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©2015 by ICAR-CIBA, Chennai; Can be used by the stakeholders associated with the

development of brackishwater aquaculture in India with due acknowledgement.

Course Director

Dr. K.K. Vijayan

Director, ICAR-CIBA, Chennai

Concept and Facilitation

Dr. T.K. Ghoshal

Principal Scientist and Officer-in-Charge, KRC of ICAR-CIBA

Conveners

Dr. Gouranga Biswas, Scientist, KRC of ICAR-CIBA

Dr. Prem Kumar, Scientist, KRC of ICAR-CIBA

Co-Conveners

Dr. Sanjoy Das, Senior Scientist, KRC of ICAR-CIBA

Ms. Christina L., Scientist, KRC of ICAR-CIBA

CIBA Special Publication No. 81

July 2015

ContentsNo. Chapter Page No.

1. Site selection, design and construction of different types of

brackishwater aquafarms 1

2. Biology of cultivable brackishwater finfishes and shellfishes 11

3. Breeding and seed production of brackishwater finfishes 30

4. Sustainable brackishwater fish culture practices 46

5. Shrimp farming with special reference to Litopenaeus vannamei

culture 61

6. Soil and water quality management in brackishwater aquaculture 69

7. Nutrition, feed formulation and feed management in brackishwater

aquaculture 82

8. Advances in mud crab farming 95

9. Concept and scope of organic brackishwater aquafarming 101

10. Brackishwater ornamental fish culture 114

11. Biosecurity and best management practices in shrimp aquaculture 121

12. Application of periphyton and biofloc technologies- new opportunities

in brackishwater farming 126

13. Brackishwater fish and crustacean diseases and their control 134

14. Fish health management in brackishwater aquaculture with special

reference to emerging diseases 152

15. Application of genetics and biotechnological tools in aquaculture 161

16. Policies and guidelines for sustainable coastal aquaculture 168

Training Manual on Sustainable Brackishwater Aquaculture Practices, 21–25 July 2015

1

Site Selection, Design and Construction of

Different Types of Brackishwater Aquafarms

Gouranga Biswas, Prem Kumar and Christina L.

Kakdwip Research Centre of ICAR-CIBA, Kakdwip, West Bengal

1.1. Introduction

India is bestowed with 1.2 million ha potential area for development of brackishwater

aquaculture and only 15–16% of the area has so far been brought under culture. With good

number of candidate species like shrimps, crabs and finfishes available in the country,

there is a vast scope for development of brackishwater aquaculture. However, level of

intensification and lack of awareness about the management practices has attributed to the

disease outbreak and severe economic losses to the brackishwater aquaculture industry.

Moreover, improper site selection, lack of good layout plan and design and faulty

construction of farm result in various environmental issues like salinization of agricultural

lands and drinking water, destruction and conversion of ecologically sensitive mangrove

areas etc. Therefore, besides technological aspects of the culture, the environmental and

socio-economical aspects need to be considered before finalizing the site for brackishwater

farms.

1.2. Site selection

Selection of a suitable site is the first and foremost step in the design and construction of

an aquafarm. A mistake made during site selection may result in higher cost of

construction and culture operation, and create environmental problems as well. A suitable

site provides optimum conditions for the growth of species cultured at the targeted

production level, given an effective pond design and support facilities. Proper guidelines

are to be followed for integrating coastal aquaculture with the local environment and

social settings. The following factors are to be considered in order to select a best possible

site for brackishwater aquaculture.

1


2

1.2.1. Main factors

1.2.1.1. Topography and tidal amplitude

Topography refers to changes in the surface elevation of natural ground, i.e. whether the

ground is flat, sloping, undulating or hilly. The best area for brackishwater ponds is where

the ground is leveled (flat) or there is a slight slope between 0.5–1.0% and not > 2%. It

should be rectangular/ square shaped flat areas near brackishwater sources like creek,

rivers, canals etc. and there may be natural ground elevation of 1–3 m above MSL having

no or minimum vegetation. Preference should be given for gravity flow of water to

facilitate easy pond bottom drying and proper water exchange. Excessive undulating

topography should be avoided as it increases cost of construction.

Average tidal amplitude of 1.5–2.0 m is ideal for brackishwater farms. Sites having

tidal fluctuation > 4 m and < 1 m should be avoided as it can cause difficulty in water

filling and drainage. The site should be minimum 50 m away from creek to avoid soil

erosion.

1.2.1.2. Type of soil and its quality

Soil is one of the most important components of a brackishwater culture system. Soil

quality should be analyzed for pH, permeability, bearing capacity, nutrient status and

heavy metal content. Permeability or water retention capacity of soil depends on the soil

texture. A soil permeability of < 510-6

m/sec is desirable. Clayey loam soil is ideal for

brackishwater farms as it has low permeability and high fertility. Clayey loam contains

textural components like sand: 20–45%, silt: 15–23% and clay: 27–40%. Area containing

sandy soil should be avoided as it causes seepage and salinization problems. Soil with pH

below 5 and high concentration of heavy metals should be avoided. Also, soil containing

organic matter layer > 0.6 m is unsuitable. Again the area affected with acid sulphate soils

(pH 2.5–5.0) should be rejected. The desirable soil parameters are as follows:

Sl. No. Parameter Optimum range

1. pH 6.5–7.5

2. Organic Carbon 1.5–2.5%

3. Calcium Carbonate > 5%

4. Available Nitrogen 50–70 mg/ 100 g soil

5. Available Phosphorus 4–6 mg/ 100 g soil

6. Electrical Conductivity > 4 µmhos/ cm


3

1.2.1.3. Water source and its quality

Good quality and adequate amount of brackishwater should be available throughout the

culture period. The water source could be from brackishwater creeks/canal, lagoons or

backwaters. The quality of the water available in the site has a strong influence on the

success of the shrimp/ fish farm. Water quality parameters like pH, salinity, and dissolved

oxygen and the presence of heavy metals should be ascertained. The water source should

be free from any industrial or agricultural pollution. Wide fluctuation in salinity and pH is

detrimental to the cultured animals.

Sl. No. Water quality parameters Ideal range

1. Temperature(°C) 28–33

2. pH 7.5–8.5

3. Salinity(ppt) 15–25

4. Dissolved oxygen (ppm) > 5

5. Transparency (cm) 25–45

6. Total alkalinity (ppm) 80–200

7. Nitrite-N (ppm) < 0.01

8. Nitrate-N (ppm) < 0.03

9. Ammonia-N (ppm) < 0.01

10. Mercury (ppm) < 0.001

11. Cadmium (ppm) < 0.01

12. Chromium, Copper, Zinc (ppm) < 0.1

1.2.2. Other miscellaneous factors

The following factors need to be considered before selecting a site:

i) Environmental (Meteorological) factors for climatic conditions, storms, etc.

ii) Accessibility of the site

iii) Socio-economic conditions of the locality

iv) Pollution problems

v) Availability of seed from vicinity

vi) Availability of freshwater and power supply

vii) Transportation and marketing facilities of the farm produce

viii) Social and political factors

ix) Technical guidance


4

1.3. Design of brackishwater aquafarms

To make functionally efficient and economically viable fish farm there should be sound

design following scientific and engineering aspects. Brackishwater aquafarms are

classified into 3 groups as follows:

1.3.1. Tide-fed farms

Tide-fed farms are best suited for traditional extensive systems. It is suitable at places

where mean spring tide ranges in between 1.3–2.0 m. Invariably, tide-fed aquafarms

require only one water channel, i.e. feeder channel-cum-drainage channel. There should be

a main sluice gate to control the flow of water in the farm. Every pond of the farm needs

individual sluice for water exchange. This type of farm is expensive on investment but

economical in operation.

1.3.2. Pump-fed farms

Pump-fed farms are best suited for semi-intensive and intensive systems. Pump-fed farms

generally have separate water channel and drainage channel. It also requires a storage-

cum-sedimentation tank (reservoir) and an efficient pumping unit. It does not require big

main sluice gate. It is suitable at places where tidal amplitude is either very high (> 2 m) or

low (< 0.8 m). This type of farm is economical on investment but expensive in operation.

1.3.3. Tide-cum-pump fed farms

The places where tidal water is available only during some months, tide-cum-pump fed

farms are suitable. A site having mean spring tide range between 0.8 to 1.3 m with ground

levels at about low spring tide levels is suitable for this farm. It requires main sluice gate

and individual pond sluices like in the case of tide-fed farm. In addition pumping unit is

required for supplying the water during the shortage of water. The tide-cum-pump fed

farm is expensive on whole because of heavy investment and operation.

1.3.4. Orientation of the farm

Overall total shape of the farm area should be more squarish than oblong to minimize the

cost on peripheral dyke. Cost of construction of squarish pond is cheaper than the

rectangular pond.


5

1.3.5. Design and construction of dike

1.3.5.1. Types of dike

There are two types of dike-

i) Periphery dike: It is the protective cover to the whole farm. Pond size, high flood

level, slope of pond bottom, vehicular load etc. are important factors to be

considered in the design.

ii) Internal dike (Secondary dike): It is the partition between two ponds. Water depth

for culture plays an important role in the design of an internal dike.

1.3.5.2. Cross sectional area and quantity of earth for a dike

Cross sectional area (trapezoidal) of a dike is calculated by using following formula-

A= Bd + Sd2

Where, B= Width of dike (Crest)

d= Depth

S= Slope (H:V)

Total quantity of earth (Q) for a dike can be calculated as-

Q = L A

Where, L = Length of a dike

A = Cross sectional area

Slope (s)

Here, slope=1:1

Top width/ Crest (B)

Height (d)

H

V

C/S Area= Bd+Sd2

Fig. - Cross section of a dike


6

1.3.5.3. Free board

Free board is provided as a safety factor to prevent overtopping of dike. Free board is

defined as the vertical distance between crest after settlement and the surface of water

level in the pond at its design depth. It is maintained as minimum of 0.6 m for periphery

dike and 0.3 m for internal dike.

1.3.5.4. Side slope

Side slope of pond dike depends mainly on soil texture and prevailing site conditions.

Flatter slope provides more stability. Ideal slope is 1.5:1 to 2:1 (H:V).

1.3.5.5. Top width

The top width or crest of dike depends on the height of dike and its purpose. It generally

varies from 1.5 to 2.5 m. When the dike is used as a roadway, minimum 3.7 m top width is

provided.

1.3.5.6. Dike protection

Dike is constructed by putting earth layers of not more than 30 cm soil with proper

compaction and consolidation of each layer. Slopes of dike should be lined with suitable

lining materials, like stone pitching, brick tiling, concrete slabs, lime concrete mixtures,

polymer based chemicals, etc. to prevent soil erosion.

1.3.6. Layout and design of ponds

As per Coastal Aquaculture Authority (CAA) guidelines, 60% of total farm area should be

water spread, rest 40% for other purposes. There are two types of ponds based on mode of

construction-

i) Embankment pond: It is also called as watershed pond. It is constructed by erecting

a dam/ levee/ dike around a small water course.

ii) Excavated pond: It is constructed by digging trenches in the ground and building

dike around it.

1.3.6.1. Shape, size and depth of ponds

Pond shape may be rectangular/ square, but rectangular is preferred for fish culture. For

rectangular pond the ratio of length and breadth should be 1.5:1 to 2:1 (L:B). Square

shaped pond for shrimp culture provides better uniform aeration. Pond size may be 0.5–


7

1.0 ha for better management point of view. Pond depth depends mainly on the species to

be cultured, topography of the area and the climatic conditions.

Sl. No. Species to be cultured Pond depth (m)

1. Shrimp 1.0–1.5

2. Fish 1.0–2.0

1.3.6.2. Types of pond

Based on the culture operation there are three types of pond-

i) Nursery ponds: 10–15% of total water spread area is kept for nursery ponds with

size 0.05–0.1 ha for fish and 0.5 ha for shrimp with 0.8–1.0 m depth.

ii) Stocking/ grow-out ponds: About 60–65% of total productive area is kept for

grow-out ponds with 0.5–1.0 ha size. These ponds should have one inlet and one

outlet placed diagonally. Corners of the ponds are made round and smooth for

better circulation of water and to prevent soil erosion in the corners.

iii) Bio-ponds/ Effluent treatment ponds (ETP): As per CAA guidelines, 10% of the

water area is to be converted into ETP when the farm area is > 5 ha and this pond

can be used for secondary fish culture.

1.3.6.3. Berm

A berm is step like structure constructed between dike base and top. It mainly helps in

preventing soil erosion from dike. It also helps in easy netting operation.

Crest

Berm

Pond

Dike

Pond bed level

Fig. - Berm


8

1.3.7. Water intake and supply system

Design of water intake and supply canal depends on the daily water requirement.

Depending on the soil quality, earthen/ stone pitched/ concrete canal can be designed.

PVC pipes (10–12 inch dia) can be used for the water supply system. While designing

sluice gate it is essential to consider tidal fluctuation in order to ensure effective control of

water flow to fill the ponds within 4–6 hours. Sluice gates are classified in to main sluice

gate and secondary gates. Main sluice gates are situated at the periphery dike and

secondary gates are in the individual ponds. Wooden shutters are used to regulate the entry

and exit of water flow into the ponds. The coarse and fine meshed screens are used in the

outlet sluice gate to prevent the entry of unwanted organisms. Separate inlets and outlets

should be constructed and must be diagonally placed for proper drainage.

1.3.8. Drainage systems

1.3.8.1. Outlets

Outlet sluice constructed on the dike opposite to inlet point is used for water drainage from

pond. It may be rectangular masonry monk type with provisions of nylon screens and

wooden plank shutters to drain water completely from pond to drainage canal. Slope from

inlet to outlet is kept as 1:1000.

1.3.8.2. Drainage canal

Earthen or lined drainage canals with a minimum bed width of 0.3 m and bed slope of

1:1500 (V:H) should be 0.3 m below pond bottom level and 0.3 m above the lowest low

tide level (LLTL) at the end of canal.

Main sluice gate Secondary sluice gates


9

1.4. Construction of farm

Farm construction requires proper planning, careful supervision and skilled workmanship.

The sequence of operations followed in farm construction is mentioned below.

i) Land clearing: There are three types of land clearing methods- manual,

mechanical and chemical clearing

ii) Land marking: Dry white powder is used to mark the positions of dikes,

channels, ponds etc. to be constructed.

iii) Excavation: Either manually or mechanically

iv) Construction of dikes and sluices

v) Construction of ponds

vi) Construction of water channels and drainage units

vii) Lining of dike slopes: With stone pitching/ brick pitching/ cement concrete

lining/ stone slab lining/ polyethylene paper lining/ growing grass, etc.

viii) Office, lab, store room, etc.

ix) Construction of residence, watchman shed etc.

1.5. CAA guidelines for construction of brackishwater aquafarms

i) Mangroves, agri lands, saltpans, sanctuaries, etc. should not be converted into

brackishwater farms.

ii) The farm should be 100 m away from a village with < 500 population, 300 m

away from a village with > 500 people and 2 km from towns, heritage areas.

iii) It should be 100 m away from drinking water source.

iv) The farm should not be located across natural drainage canals/ flood drain.

v) Traditional activities like fishing should not be interfered while using creeks,

canals, etc.

vi) Space between two adjacent farms: 20 m for small farms, 100–150 m for bigger

farms.

vii) Farm should be minimum 50–100 m away from the nearest agri land.

viii) Water spread area of farm should not exceed 60%, rest 40% for other purposes.

ix) Areas with many farms should be avoided.


10

Fig. 1. Layout of a brackishwater farm

(Source: CIBA Extension Bulletin)

Fig. 2. Model layout of a shrimp farm (Source: MPDEA)


11

Biology of Cultivable Brackishwater

Finfishes and Shellfishes

Prem Kumar, Gouranga Biswas, Krishna Sukumaran* and Babita

Mandal*


*ICAR-Central Institute of Brackishwater Aquaculture, Chennai

2.1. Introduction

The brackishwater environment is endowed with vast and varied natural resources.

However, commercial farming of finfish and shellfishes are restricted to only few species

due to some important factors, viz., economic importance, growth rate, culture

compatibility, seed availability etc. It is necessary to have knowledge on basic biology of

any animal before undertaking their husbandry and maintenance. Cultivable brackishwater

shellfishes include mostly penaeid shrimps and brachyuran mud crabs. The main cultured

penaeid shrimps in India are the giant tiger shrimp (Penaeusmonodon), the Indian white

shrimp (Fenneropenaeus indicus), and the banana shrimp (F. merguiensis). The whiteleg

shrimp (Litopenaeus vannamei) has been introduced recently. Among the 700 marine

littoral crabs of India, only two species of mud crabs, Scylla serrata and S. olivacea are

commercially cultured in brackishwater ponds. Cultured shrimps and live mud crabs

continue to be the main shellfish commodities in export market. The important

brackishwater fishes include Asian seabass (Lates calcarifer), grey mullet (Mugil

cephalus), milkfish (Chanos chanos), pearlspot (Etroplus suratensis) etc.

Here, biology of some brackishwater finfish and shellfish species having economic

importance is discussed.

2.2. Biology of finfishes

2.2.1. Biology of Lates calcarifer

The Asian seabass, L. calcarifer is an esteemed food fish which belongs to the family

Centropomidae.

2


12

Food and feeding habits

Adult seabass is carnivorous in nature. However, juveniles are omnivores. It is

opportunistic predator and its diet changes with size. Stomach contents of smaller fish (1–

10 cm) showed 20% phytoplankton and 80% fish, shrimp etc. In bigger fish (20 cm), the

gut contained 100% animal prey (70% crustaceans and 30% fishes). It prefers pelagic

fishes than benthic crustaceans. It also has cannibalistic habit.

Size at maturity

Seabass is a protandrous hermaphrodite fish. Majority of individuals from early age

groups are males weighing 2.0–3.5 kg body weight, but after attaining 4 kg and above (4

years old), the majority of them become females. Males attain maturity at 25 cm in total

length and females mature at the size of 65–85 cm.

Maturation

Gonadal development is very rapid just before spawning and coincides with fast growth.

The gonads are strongly dimorphic and the gonad size varies in different growth stages.

Usually, oocytes in the posterior end of ovary are larger in size than the oocytes of anterior

region indicating the process of continuous ovarian development and occurrence of

multiple spawning. In fully mature females, the diameter of oocyte usually ranges from

0.45-0.53 mm.

Spawning season

Spawning season of seabass extends from April to November in Indian waters. Spawning

takes place in sea. In multiple batches, eggs are released continuously up to 3 days.

Fertilized eggs are usually transparent, pelagic and easily drifted by tides towards coastal

areas for larval development. Restoration of gonads takes place during onset of north east

monsoon in the Indian east coast.

Sex ratio

In induced breeding operation, sex ratio of 2:1 (male to female) is maintained for proper

fertilization.

Fecundity

Fecundity of seabass varies from 1.0 to 20.0 million eggs depending on the size and

weight of fish.


13

Age and growth

Normally, fish attains 0.8–1.0 kg in the first year and 2 kg in the second year. Sometimes

large size seabass even up to 6 kg is caught from estuaries and inshore waters using hook

and line. It shows wide growth variations under culture condition. Even though same size

group seed stocked together, due to natural differential growth in the first year itself, fish

are available from 0.4 to 4 kg indicating its growth potential.

2.2.2. Biology of Chanos chanos

It is an important fish from aquaculture view point and cultured in large scale in South

East Asia. Milkfish, C. chanos is the only member of the family Chanidae under order

Gonorynchiformes. Milkfish is one of the most important brackishwater cultivable food

fish species around the world which is well studied by researchers in the past. It is having

good demand in South East Asian countries like the Philippines, Indonesia and Taiwan as

well as a readily available good domestic market in India also. It is called as Paal Meen in

Tamil, Pala Bontha and Tulli Chepa in Telugu, Poomeen in Malayalam, Hoomeenu in

Kannada, Golsi in Goa and Seba khainga in Oriya. Milkfish is easy to culture with low

operational cost due to its feeding habit and less disease occurrence. It can survive in

salinities ranging from 0 to 100 ppt. It can grow rapidly in brackishwater by feeding on

algae and phytoplankton. It is considered as food fish as well as bait fish for tuna fishery.


Milkfish is an herbivorous fish but their larvae feed mainly on zooplankton. Juveniles and

adults eat cyanobacteria, soft algae (Cyanophyta, Lyngbya spp. and diatoms), small

benthic invertebrates, decayed organic matter and even pelagic fish eggs and larvae. The

plant-animal complex, namely lab-lab formed in shallow water is one of the preferred

food items. It has fine gill rackers and long intestinal tract which help in retaining and

digesting this kinds of food ingested. They can be adapted to accept artificial diet very

easily.

Size at maturity

They attain maturity at an age of 5–7 years in captive condition with body weight of 3 kg

and above.


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Spawning season

In Indian peninsular coast, milkfish spawns during December to May. Seed collection

centres are on east coast, Rameswaram, Mandapam and Pulikat Lake in Tamil Nadu and

Cochin coast in Kerala on the west coast.

Spawning

Spawning takes place in offshore waters, 15–30 km away from the shore at a depth of 20–

30 m in clear water over sandy or coral bed. Milkfish reaches gonadal maturity in open sea

after attaining 4–5 years of age. There is no distinct morphological difference between

milkfish of opposite sex. Milkfish is a highly fecund species (0.3 to 1 million eggs/kg

body weight). Mature ovaries usually comprise around 10–15% of the body weight of the

spawner. In wild, milkfish spawns more than once a year. The natural spawning season

extends from April to September. In wild, spawning occurs near the sea surface (30~40 m

in depth), and the female produces millions of eggs that hatch within 24 h into yolk sac

larvae. Spawning occurs around new and full moon phases, most often at night (probably

after midnight). It spawns in big shoals in open sea. Eggs are pelagic and comes near shore

area where they hatch and hatchlings gets its nutrition and become fry and fingerling.

Fecundity

Induced maturation and spawning have been successfully done in the Philippines, Taiwan

and Indonesia in past. ICAR-CIBA has also achieved success in captive broodstock

maturation which resulted in successful spawning and fertilization very recently.

Habitat and growth

It is a euryhaline species which can withstand sudden changes in salinity and can be grown

in fresh, brackish and marine waters. Its salinity tolerance limit is 0 to 100 ppt. It can

tolerate a temperature range of 15–40°C, but the optimum is between 20°C and 33°C.

Milkfish is a marine species with catadromous migratory habit. Adults spend part of their

lives in littoral waters and go to sea for breeding. In nature, it grows to a maximum of 1.5

m. In well maintained culture ponds, it grows to a marketable size of 300–400 g in 3–4

months.

2.2.3. Biology of Mugil cephalus

The striped mullet, jumping grey mullet, or the flathead mullet M. cephalus is the most

important species of the grey mullets which belong to the family Mugilidae, which has 20


15

genera and 70 valid species, 11 of which belong to the genus Mugil. Grey mullet enjoys a

cosmopolitan yet discontinuous distribution. It is euryhaline and its salinity tolerance

ranges from fresh to hypersaline waters. Similarly, it can withstand a wide range of

dissolved oxygen conditions, including very low dissolved oxygen levels when the fish

may switch to anaerobic metabolism to swim through hypoxic waters. The grey mullet is

often observed to ventilate water in contact with the air in an adaptive process called the

aquatic surface respiration (ASR). It is also tolerant to a wide range of turbidities 10-80

NTU. It is important commercially not just as a food fish but also because of its roe which

is marketed as Botarga caviar in Japan and Taiwan.


Larvae and fry of less than 30 mm feed principally on zooplankton. The juveniles feed

preferably on diatoms and epiphytic cyanophyceae. Gut contents of adult consist of sand,

decayed organic matter, diatoms, dinoflagellates, foraminifera, algae and miscellaneous

items like copepods and tintinnids. Qualitative composition of gut contents says that it is

an iliophagous subsisting mainly on decayed organic matter. They feed in a head down

position, moving its head from side to side. The movement sometimes is so vigorous that

the whole body shakes, as a result a cloud of mud along with soft flocculant matters rich in

microorganisms are sucked through its protrusible mouth. Although it can adapt itself to

artificial diet, it has a preference to natural food.

Size at maturity

The age at sexual maturity of the fish varies widely, varying from first year to eighth year

in both sexes, and size at maturity in males varies from 230 to 400 mm and in females

from 240 to 415 mm. However, the most commonly accepted age at first maturity is two

years for males and three years for females.

Maturation

Ova of different maturity stages are found, but only one distinct group of mature ova with

a wide range of size indicates that the fish has a single spawning and is group synchronous

in nature. The eggs with 0.6 mm diameter are fully ripened.

Spawning season

The spawning season in India is from October to May and the fry availability along the

coastal regions is very seasonal. In Kerala, fry availability is from June to August in the


16

Puduvypu region. In Pulicat Lake, seeds are available during January to March. In West

Bengal coast, grey mullet seeds availability is found from February to April.

Spawning

Spawning occurs in offshore waters where warm water current exists with surface water

temperature of 20–23°C during spawning season.

Sex ratio

Globally, the commonly reported sex ratios for grey mullet shoals are quite balanced, very

close to a 1:1 ratio. Sex ratio in Pulicat Lake was found to be 1.56:1.00 for male to female.

Fecundity

The estimated fecundity of Pulicat Lake M.Cephalus female ranged from 4.34 to 47.17

lakh eggs per female. The annual fecundity has been recorded between 1.2 to 3.6 million

by most authors.

Migration

M. cephalus undergoes 3 types of migrations in its life history. A) Osmoregulatory

migration: a phenomenon of juveniles anadromously migrating towards estuaries, B)

Seaweed migration: adult mullets migrating towards open sea after being in estuaries for

gonadal maturity, C) Spawning migration: the ripe mullets migrating in schools from

feeding grounds to spawning grounds in a particular direction.

Age, growth and habitat

The maximum size reported is 1.2 m and the most common marketable size is 500–800 g

(30–50 cm). The rate of growth is highly variable depending on the climatic and

environmental conditions. When cultured with Indian major carps, they can grow up to 40

cm in a year. It is a eurythermal and euryhaline species. The maximum temperature

tolerance limit is 40°C. It can be cultured in waters with salinities ranging from 0 to 145

ppt.

2.2.4. Biology of Tenualosa ilisha

Hilsa shad, Tenualosa ilisha is a high value fish, popularly known as Hilsa. The fish

spends its adult life in the marine environment and migrates to freshwater riverine habitats

for breeding (anadromous). Hydrological alterations in the form of barrages and dams

built across the major rivers, especially along Ganges, Narmada have blocked its


17

migratory routes to breeding grounds in riverine areas, resulting in collapse of its fishery

in the river.


The fish is planktonic feeder, without any food preference and subsists on whatever

planktonic feed available in the environment. Young ones fed on copepods, cladocerans

were the next important group. Adult hilsa feeds mainly on copepods, organic matter,

green algae, diatoms, rotifers in the order of preference.

Maturity and breeding season

Dey (1986) revealed that females below 300 mm size were hardly found to take part in

spawning activity. The smallest mature females observed in Hooghly estuary were around

341 mm (av. wt. 550 g). Ruben et al. (1992) reported that the size at first maturity at 37

mm, at the age of approximately 2 years. However, some of the recent observations

suggested attainment of maturity even at 160–170 mm. Maximum percentages of larger

oocytes found in ovary during August-October and a minor peak during January, which

indicate the breeding season.

Sex ratio

Sex ratio of Hooghly hilsa, is 1:1 (Jones and Menon, 1951).

Spawning

Hooghly hilsa spawns intermittently and the fish has two distinct breeding seasons but the

same fish do not spawn twice in a year. The prolonged availability of hilsa seeds in the

Hooghly estuary during August to March with peak in October and November indicates

that the spawning of the species do not take place simultaneously in all the individuals of

the same school. This indicates that the spawning is not group synchronous type.

Breeding

Wilson (1909) was the first to achieve success in artificial fertilizing hilsa eggs (1917).

Sen et al. (1990) successfully bred the fish through stripping method.

2.2.5. Biology of brackishwater catfish, Mystus gulio

M. gulio is commonly used as a food fish and has occasionally been caught and exported

as an ornamental fish (Ng, 2010). It is known as Nuna-tengra in Bangladesh (Rahman,

1989), Kala-tenguah or Nona Tengra in India (Daniels, 2002), Long-whiskered catfish in


18

Sri Lanka (Pethiyagoda, 1991) and Nga-zin in Myanmar (Khin, 1948). This small

indigenous fish contains high nutritional value in terms of protein, micronutrients,

vitamins and minerals which are not usually found in other foods making it a very

favourable candidate for aquaculture in southeast Asia (Ross et al., 2003).

Identification

Body is elongated and compressed with a rough and granulated upper surface. Head is

depressed. There are four pairs of barbells and maxillary one extends to the end of pelvic

fin. Adipose fin is small and caudal fin is forked. D. 1/7; P1. 1/8-9; P2. 6; A.12-15

(Rahman, 1989).

Distribution

M. gulio is found in south and Southeast Asian countries including Bangladesh, India,

Myanmar, Pakistan, Sri Lanka, Indonesia, Malaysia, Singapore, Thailand and Viet Nam

(Ng, 2010).

Food and feeding

This species inhabits estuaries, tidal rivers and lakes, ascending to freshwater, often

entering the sea (Talwar and Jhingran, 1991). Its food mainly consists of crustaceans and

insects (Pandian, 1968).

Spawning season

Spawning season varied from March to November (Sarker et al., 2002). The absolute

fecundity varied from 11,436 (10 cm TL fish) to 23,481 (22 cm TL fish) in Bangladesh

(Sarker et al., 2002). Fecundity of the M. gulio was found to range from 3,891 to 1,68,358

with an average of 32,000.

Sexual maturity

The total length and weight of the male fish ranged from 10.5 to 20.6 cm and 18 to 102 g,

respectively, whereas it was 12.3 to 24.5 cm and 20 to 205 g, respectively in case of

female. GSI values of both male and female were found to increase from March onwards

reaching a peak in July followed by a gradual decrease up to December.

2.2.6. Biology of Goldspot mullet, Liza parsia

The fish Liza parsia (Ham.), belonging to the family Mugilidae commonly known as

goldspot mullet, is a catadromous fish and widely distributed in the coastal waters of

tropical and sub-tropical regions extending from 420N to 420S (Talwar and Jhingran,

2001; Nash and Shehadeh, 1980). This brackishwater fish species commonly available in


19

shallow coastal waters, estuary and mangrove swamps, is one of the most favourite, tasty

and commercially important fishes in Bangladesh as well as in Southeast Asia, India and

many parts of central and South America.

Sexual maturity and spawning

The maximum GSI values obtained for male and female were 1.49 and 14.71,

respectively. On the basis of GSI values, the reproduction period of L. parsia was found to

extend from November to March with two peaks in the months of December and

February. Rheman et al. (2002) reported that female L. parsia has maximum GSI values

(16.7) in December and this species spawned for several months with two spawning peaks

in the month of December and February. The egg diameter of L. parsia reached 0.49 mm

in December and 0.5 mm in February.

Fecundity

Fecundity of L. parsia was found to range from 18,950 to 1,71,210.

2.2.7. Biology of cobia (Rachycentron canadum)

Cobia, Rachycentron canadum (Goode 1884) is considered as one of the most promising

candidate species for warm water marine aquaculture in the world (Franks et al., 2001;

Liao et al., 2004; Benetti et al., 2007, 2010), owing to its extraordinary growth rate,

adaptability for captive breeding, low cost of production, good meat quality, high market

demand, especially for sashimi industry and overall aquaculture performance.

Distribution

Cobia is a pelagic fish that is found throughout most of the warm ocean waters of the

world, except for the Pacific coast of North America (Migdalski and Fichter, 1983). Cobia,

the only member of the family Rachycentridae, is found in the warm temperate to tropical

waters of the West and East Atlantic, throughout the Caribbean and in the Indo-Pacific off

India, Australia and Japan (Shaffer and Nakamura, 1989; DuPaul et al., 1997).

Sexual maturity

Sexual maturity is reported in 1–2 years old males and in females of 2–3 years, with

females growing larger and faster with maximum sizes up to 60 kg.

Fecundity

The number of eggs produced in each spawning by a female weighing 15 kg ranges from 2

to 3 million (Xan, 2005).


20

Spawning

The species has protracted spawning season (March to September in Indian seas) and it

can spawn in captivity. The freshly spawned eggs measured 1.0–1.1 mm in diameter. They

were yellowish brown in colour with one prominent oil globule. All the fertilized eggs

were found floating.

Culture potential

Under culture conditions, cobia can reach 3–4 kg body weight in one year and 8–10 kg in

two years.

2.2.8. Biology of Etroplus suratensis

The pearlspot, E. suratensis belonging to the family Cichlidae is also referred to as green

chromide and has high market value in the southern states of India, especially Kerala.

Pearlspot is naturally distributed in peninsular India and Sri Lanka. It is of the three

indigenous cichlids of our country along with the orange chromide E. maculatus and the

Canara pearlspot E. canarensis.


Young ones feed almost on zooplankton, but from juvenile stage onwards, they are mainly

herbivorous and detritivorous and feed on algal weeds, filamentous algae, detritus etc.

However, miscellaneous food items such as insects, molluscs, crustaceans and sponges

also form part of its food. The fish is commonly observed to exhibit scraping behaviour,

hence periphyton substrates can be effectively utilized during its culture.

Size at maturity

The fish attains maturity at 8-9 months of age and the size at maturity varies from 10.5–

18.0 cm.

Maturation

There are different maturity stages of gonads, viz. immature, maturing, ripening, ripe and

spent. At ripe stage ovaries measure 30–52 mm in length with largest group of ova of 2

mm diameter. Whereas, for male, testes measures 32–48 mm in length and with little

pressure, milt oozes out. Different size groups of ova are observed in mature fish

indicative of its asynchronous spawning nature.


21

Spawning season

It breeds throughout the year but two peaks have been noticed, one from December to

February and the other from July to August. Some authors have co-related this with the

cessation of monsoons.

Breeding behaviour

The breeding behaviour of pearlspot is complex involving courtship, pairing, nest-building

and parental care. Before pair formation they move in group and courtship starts between

some members of the groups and pairs are formed. Nest-building occurs in preparation of

the nest for laying the eggs. Eggs are attached to hard substrates and thereafter the larvae

are deposited in the nest and commonly 1000–2000 larvae are observed. Parental care

involves care of the eggs and the young ones. An incubation period of 72 h is commonly

observed. The newly hatched larvae are picked up by mother into her mouth and

transferred to pits measuring 6–8 cm diameter with 2–3 cm depth. These pits are made

ready before the eggs hatch out. Parents actively produce a constant current near pits by

fanning with fins. After yolk sac absorption, the larvae are led out as the pectoral fins

become functional. Parental care lasts for a considerable time even after the young ones

assume adult forms (up to 40 to 50 mm).

Sex ratio

Females dominate over males in natural waters. The sex ratio in different size groups was

reported as 1:0.84 to 2.73:1 (female:male) from Indian coast.

Fecundity

In general, the fecundity of perlspot is low ranging from 500 to 6000. But it also depends

on various parameters such as fish size, ovary size.

Age and growth

Males are bigger than females and exhibit better growth rate (150–175 mm/ 125–150 g in

a year). It can grow over 30 cm in length and 1.35 kg in weight under favourable

conditions. In Chilka lake areas they grow up to 105 mm in the first year.

2.2.9. Biology of Scatophagus argus

The spotted scat, S. argus is a euryhaline teleost widely distributed in near shore waters of

Indo-Pacific region. It is a popular aquarium fish and an important food fish in its

available areas.


22

Food and feeding habit

The binomial nomenclature Scatophagus argus is translated from Greek as „spotted

faeces-eater‟, and was derived from the habit of scat to gather in harbours and feed on

offal and other wastes dumped from ships. It is uncertain, however, if scats are true

coprophages since their acceptance and/or preference for faecal matter has not been

confirmed. Gut content analysis revealed that adult scats are primarily herbivorous. They

accept green filamentous algae and brown seaweeds also. Worms, crustaceans and insects

constitute part of their food items. The evidence of herbivorous food habit is supported by

presence of their long coiled intestine approximately 3.5 times the body length.

Sex determination

Sexes can be differentiated by head shape. In females, head profile ascends at a constant

slope, whereas males have a concave curvature of the head above the eye. This difference

is more prominent in larger fish of 100 g and above. In addition, females are often a lighter

olive green colour compared to darker males.

Size at first maturity

Size at first maturity varies with sexes. Females with 14 cm (150 g) and males with 11.5

cm (83.5 g) standard lengths show first sexual maturity.

Spawning season

In West Bengal coast, the fish spawns from June to August during prevalence of south-

west monsoon wind.

Spawning

Spawning occurs in water with salinity of 25 ppt or more in river mouth or estuarine areas.

Sizes of spawned eggs are of 0.68–0.75 mm diameter. The eggs are transparent and

spherical containing a single oil droplet of 0.30 mm diameter.

Tholichthys larvae

Scat larvae pass through a developmental stage known as tholichthys. This stage is a

unique feature of few genera of teleost, including butterfly fish (Chaetodontidae) and scats

(Scatophagidae). These larvae are deep bodied and laterally compressed. They are usually

very dark, have rough and scaleless skin and a well developed lateral line. Their size

ranges from 0.6 to 1.2 cm. The most distinctive feature of these larvae is bony plate which


23

completely encases the head in a thick protective sheath. One of these plates dorsal to the

eye has posteriorly oriented projections which form spiny horns on either side of the head.

These plates are slowly absorbed as the tholichthys larvae metamorphose into juvenile

forms.

2.3. Biology of shellfishes

2.3.1. Biology of commercially important penaeid shrimps

The family of Penaeid shrimps consists of approximately 110 species, of which 10 species

are important for commercial culture. Shrimp farming in India is dominated with Penaeus

monodon, the declined production of this species is compensated by Litopenaus vannamei,

which was introduced in India in the year 2009.

Distribution

Penaeid shrimps are widely distributed in Indo-west Pacific water bodies. They are mainly

cultured in coastal and off shore waters of both eastern and western hemisphere.

Habitat

Adult penaeid shrimps generally found in off-shore waters and spwan in the salinity

regime of 30-35 ppt at a depth of 30-100 m. Juveniles often prefer brackishwaters of

estuaries and coastal wetlands, while larval stages inhabit plankton-rich surface waters off-

shore, with an on-shore migration as growth advances.

Morphology

The morphology of penaeid shrimp consists of carapase (head), abdomen (body) and

telson (tail). The sexes are separate and identified by secondary sexual characters. In male,

the endopods of first pair of pleopods (swimming legs) appear initially as leaf like and

later develop into semicylindrical tubes. The tube like structures fuse together when the

shrimp attains the maturity and is called as petasma. In female external genetilia is called

as thelycum, placed at the base of last three walking legs. Thelycum is only pouch where

spermatophores are stored at the time of mating. In Penaeus species, the rostrum has

dorsal and ventral teeth, whereas, the dorsal teeth only present in the genera of the family

metapenaeidae. The rostrum extends beyond the tip of the antennular peduncles and has

generally 6–8 dorsal and 2–4 ventral teeth. In penaeids, adrostral carina reaches almost to

the tip of epigastric tooth and carina reaches to the posteriar edge of the carapace. The


24

abdomen is carinated dorsally from the anterior one third of the 4th

to 6th

somites and the

telson is unarmed.

Life cycle

The penaeid life cycle includes several distinct stages and they are generally found in a

variety of habitats. Adults migrate to the sea for breeding. During spawning, eggs and

sperm are simultaneously released from the female and male. Fertilization is external, and

egg development occurs in the water column.

The fertilized eggs are demersal and hatch

within 14 h to strongly phototropic nauplii (6

sub-stages, each moults every 4–6 h

intervals), which swim towards the surface.

After 36 h, the larvae pass through distinct

stages, protozoea (3 sub-stages, each moults at

1 day intervals) and mysis (3 sub-stages, each

moults at 1 day intervals), before metamorphosing into postlarval shrimp. Larvae are

planktonic. The early post larvae (PL) become benthic and are adapted to tolerate wide

range of salinity fluctuation. So, PL and juveniles migrate to brackishwaters of estuaries

and coastal water bodies.


Penaeid shrimps are known to ingest a variety of items and have been described as

omnivorous, detritus feeders and carnivores. Their diet ranges from the hereditary yolk

sack, during the early naupli stage to phytoplankton at protozoeal stage and then to

zooplankton at mysis stage. Epibenthic PL and juveniles consume both animal and plant

matters, including microalgae, detrital aggregates, macrophytes, foraminiferans,

nematodes, copepods, tanaids, larval molluscs and brachyuran larvae. As shrimps grow,

they consume mysid and caridean shrimp, amphipods, polychaetes, and molluscs, as well

as fishes. Sub-adult and adult shrimps also consume significant amount of detrital

aggregates.

Moulting

Shrimp increases in size through a physiological process called moulting (Ecdysis) cycles.

Moulting begins with an increase in concentration of moulting hormone in the

haemolymph. During moulting, a shrimp undergoes continuous process like periodically


25

loosen the connectives between their epidermis and the extracellular cuticle; rapidly

escape from the confines of this rigid cuticle; take up water to expand the new, flexible

exoskeleton; and then quickly harden it with minerals and proteins. Ecdysis, as a stage,

only lasts a few minutes. It begins with the old exoskeleton opening at the dorsal junction

of the thorax and abdomen in decapod crustaceans, and is completed when the animal

escapes from its confines. Different stages of the moulting process includes premolt

(proecdysis), moulting, postmolting and intermoult.

Digestive system

The morphology of the digestive tract in the penaeid shrimp is similar to that of most

decapods. It is divided into a complex cuticle-lined foregut region (proventriculus); a

compact digestive gland, hepatopancreas at the beginning of the midgut region, followed

by a long tubular, mid gut gland and a cuticle-lined hindgut region. The mouth leads into a

short vertical oesophagus, which opens into the lumen of the anterior of the foregut. The

proventriculus is divided into two principal chambers. The anterior chamber is distensible,

called the cardiac stomach, and has a pair of ventro-lateral plates, gastric mill and a dorsal

median tooth. The posterior chamber, pyloric stomach is much narrower which opens into

the midgut, through filter-press. The principal functions of the midgut are the secretion of

digestive enzymes and absorption of nutrients. The remainder of the midgut is a straight

tube, running from the cephalothorax dorsally through the abdomen to the rectum. The

short muscular rectum is lined by six pad-like ridges, whose primary function appears to

be for grasping the faecal pellet in the peritrophic membrane and extruding it.

Reproductive system

Penaeid shrimps are sexually dimorphic with distinct external features. The male has two

pairs of modified abdominal appendages on the first and second abdominal segments

namely the petasma and appendix masculine respectively which are modified for

spermatophore transfer to the female's external receptacle, the thelycum which is located

between the bases of the fifth walking legs. The thelycum may be "open" or "closed",

depending on the species. In closed thelyca species, thelycum is enclosed by chitinous

plates and spermatophore is placed inside the groove whereas open thelyca are not

enclosed by plates, and the spermatophore must be placed on it by a male when the

female's exoskeleton is hard. Usually females having open thelycum spawn immediately

after mating unlike closed thelycum species where there is a time lag between mating and


26

spawning. The open thelyca are found in some shrimp species endemic to the Western

Hemisphere, such as P. stylirostris and L. vannamei; while closed thelyca are

characteristic of most Asian species, such as P. monodon, P. chinensis, F. indicus and F.

merguiensis.

Internal organs of the reproductive system

Male reproductive system includes a paired testes, vas deferens and terminal ampoules for

spermatophore storage. The female reproductive system includes paired (but partially

fused) ovaries that extend from the mid-thorax to the posterior end of the abdomen, and

oviducts terminating adjacent to a single thelycum.

Litopenaeus vannamei (whiteleg shrimp/ Pacific white shrimp)

This shrimp is grayish-white in colour, commonly called as whiteleg shrimp. Unlike tiger

shrimp, this species is open thelycum-type in which seminal recepticles are present.

Penaeid shrimp can be distinguished by number of rostral teeth and L. vannamei is known

to have 8-9 teeth on the dorsal and 1-3 on the ventral side. Its distribution ranges from the

North of Peru to the North of Mexico. It is usually found on mud bottom, down to a depth

of 75 m. They grow to a maximum weight of 120 g (females). Males are relatively

smaller. Males in this species become mature from 20 g and females from 28 g onwards at

the age of 6–7 months. It is open thelycum species; hence they differ in their mating

pattern. In open thelycum species, mating takes place when the female shell already has

hardened. Both male and female cling parallel together, belly to belly. The spermatophore

is visible as coarse whitish mass of approximately 1×1 cm, glued to the thelycum. In L.

vannamei the colour of the ovary changes just before spawning, this can be used as

ripeness indicator. Absolute fecundity of wild broodstock is 5.6 million/ kg. However,

cultured L. vannamei of 50 g produced around 1.4 lakh eggs per spawn (2.8 million/ kg).

In general, ablated females spawn 1–3 times per month. Reproduction is fully controlled

and genetic improvement can be made. When the eggs are released from body, they pass

through the sperm mass and get fertilized. Females usually spawn within hours of

fertilization, mostly at night. L. vannamei weighing 30–40 g will spawn 100000–250000

eggs of approximately 0.22 mm in diameter. Floating eggs 0.2–0.3 mm in diameter drift

with the currents and develop into nauplii. Hatching occurs about 16 h after spawning and

fertilization. The first stage larvae, nauplii, swim intermittently and positively phototactic

and metamorphose through stages like that of other penaeid species.


27

2.3.2. Biology of commercially important mud crabs

Commercially important mud crabs belong to the family portunidae. The main cultivable

brackishwater mud crabs are Scylla serrata and S. olivacea. Mud crabs are generally sold

in live condition both in domestic and export market. Live and gravid female mud crabs

above 300 g size is much sought after commodity in export market.

Distribution

The mud crabs are economically and recreationally important brachyuran crabs distributed

in the shallow coastal waters, brackishwater lakes, and lagoons and inter tidal mangrove

areas of the Indo-West Pacific region.

Habitat

Adult mud crabs are generally found in muddy, mangrove-lined estuaries, and the

ovigerous females move off-shore to spawn. Crabs which have a dispersive coastal larval

stage and occur within estuaries as adults usually colonize in coastal habitats as megalopae

or postlarvae. S. serrata is free living and frequently seen in open estuaries, whereas S.

olivacea is burrowing in nature. They are mainly euryhaline in nature and able to tolerate

0–45 ppt salinity level. However, in grow-out condition they grow well in 10–30 ppt

salinity.

Sexual identification

Mud crabs are sexually dimorphic and can be distinguished once it reaches 35 mm

carapace width (CW). Abdominal flaps are slender and triangular in case of males,

whereas it is triangular and broad in female. In fully matured and berried female,

abdominal flap is semi-circular or half-moon in shape.


Mud crabs are generally carnivorous in nature. They feed on bottom dwelling animals,

small crustaceans and decayed animal matters. In culture condition, they accept

formulated feeds.

Moulting

The moulting process depends on body size, physiological and environmental factors.

During moulting animal uptakes water and minerals get absorbed from the exoskeleton

and then it is cast off. After moulting tissue gets replaced with water. The newly moulted


28

crab will be having more water in the tissue and generally known as water crabs or soft

crabs. Frequency of moulting decreases as animal age increases. Larger species generally

attains a size of 210 mm CW /2.4 kg whereas smaller ones attain a maximum size of 700

g/ 140 mm CW.

Sexual maturity and breeding

Usually, the mud crab reaches the

reproductive stage when its shell width is

greater than 7.8 cm and its body weight over

100 g. Breeding season varies all along the

coast. During mating female stores

spermatophore in its body and when eggs

become ripe they get fertilized and attached to

the pleura. Mud crabs are continuous breeders

and berried females occur throughout the

coastal waters. However, peak breeding season varies from place to place. Fecundity vary

from 2-3 million eggs in larger species and 0.2–0.3 million in smaller ones. Incubation

period is 2 weeks and during that time colour of the berry changes from orange to brown,

then to black.

Larval life cycle

There are 5 zoeal stages which moult at 2–3 days interval and one megalopa stage which

takes 11–12 days to reach first crab instar stage. Zoeal stage onwards its cannibalistic

nature commences. The megalopa larvae gradually adapt themselves to a benthic life.

Because of their phototactic behaviour, larvae are often attracted by light at night.

Further readings

Biology of Finfishes and Shellfishes by S.L. Chondar. SCSC Publishers, Howrah,

India.

Text Book of Brackishwater Fish and Shrimp Farming by Susheela Jose and K.

Jayashree Vadhyar, Kalyani Publishers, New Delhi.

Biology of Spotted Scat (Scatophagus argus) in the Philippines. Asian Fisheries

Science, 5 (1992): 163-179.


29

Biology, fishery, culture and seed production of the pearlspot Etroplus suratensis

(Bloch). CIBA Bulletin No.7, 1995.

Biology and Fishery of Important Grey Mullets of Pulicat Lake. CIBA Bulletin No.11,

1998.

Baily-Brook, J.H. and Moss, S.M., 1992. Penaeid taxonomy, biology and

zoogeography; in Marine Shrimp Culture: Principles and Practices, Fast, A.W. and

Lester, L.J. (eds.), pp. 9-27, Elsevier Science Publishers, Amsterdam, Netherlands

Kathirvel, M.; Kulasekarapandain, S; Balasubramanian, C.P. (2004). Mud crab culture

in India, CIBA bulletin No.17.

Ravichandran,P. and Pillai, S.M., 2004. Hand book of shrimp seed production and

farming,CIBA bulletin, No :16

Treece, G.D. and M.E. Yates, 1990. Laboratory manual for the culture of penaeid

shrimp larvae. Texas A&M Univ., Sea Grant College Program, Bryan, TX, Pub. 88-

202 pp.


30

Breeding and Seed Production of Brackishwater

Finfishes

Prem Kumar, Gouranga Biswas, M. Kailasam* and M. Natarajan*



3.1. Introduction

Success of aquaculture mostly depends on the availability of sufficient quality seed at the

required time. Availability of quality seed from wild sources is always unpredictable and

unreliable. Most of the cultivable fish do not breed in captivity as they fail to attain final

oocyte maturation. Hence it is necessary to go for induced breeding either by hormonal or

environmental manipulation.

3.2. Asian seabass, Lates calcarifer

Broodstock development

Success of seed production under captive condition depends upon the availability of

healthy brood fish. Seabass is a catadromous fish (adults migrate to sea for maturation and

spawning). Collection of brood fish at the right stage of maturity, transporting, holding

would cause stress and ultimately affect breeding. Hence, it is important to develop viable

broodstock under captive conditions. Since, seabass attains maturity after 2 years of age to

develop broodstock from farm grown fish; one has to wait more than 2 years. To save

time, adult fishes could be procured from the commercial catches, transported carefully to

the hatchery and maintained in holding facilities. Whether from the farm or from the wild

catches, fish have to be procured with care and transported following protocols of healthy

broodstock development. Fish are stocked @ 1 kg/ m3 in the broodstock tank after

quarantine.

Broodstock management

Quality feed in adequate quantity is a pre-requirement for obtaining healthy brooder.

Quality feed with nutritional value required for maturation and spawning will help in

attaining the purpose for which the stock is maintained. As such, seabass can be

maintained feeding with trash fishes or formulated feed. Seabass is a voracious

3


31

carnivorous fish feeding mainly on crustaceans/ small fishes in live condition. But while

maintaining in captive condition, the fish have to be slowly weaned to feed on the diet that

can be provided. In the broodstock holding tanks, fish are fed with trash fish @ 5% of the

body weight in frozen form. Fresh trash fish like tilapia (Oreochromis mossambicus),

sardines (Sardinella spp.), horse mackeral (Decapterus spp.) etc. are procured, cleaned

and packed in polythene bags of 2–4 kg block and stored in deep freezers at –20°C. At the

time of feeding, the fish are taken out, thawed, washed and fed to the fish. It is important

to provide trash fishes with addition of vitamin mix @ 2 g/ kg feed. Since squid is having

rich resources of protein, it can be supplied to fish once in a week. Feeding is done once a

day in evening hours. Excessive feeding should be avoided since the left over fish would

deteriorate the water quality. If any fish is unfed it should be removed immediately. Health

management is important aspect of broodstock management; more commonly encountered

pathogens are the monogenic parasites like Diplostomum, Caligus and Dactylogyrus spp.

etc. Prophylactic treatment with 100 ppm formalin is done at regular intervals. The

infection of parasites would be more during winter months when the water temperature is

less than 22°C. In case of higher degree of infection with parasite, treatment with 1 ppm

dichlorovas (Nuvan) may used though it is not desirable.

Selection of spawners

The gonadal condition is assessed by ovarian biopsy. Female with ova diameter above 450

µ are selected. Male with oozing milt when the abdomen is gently pressed is selected.

Brood fish selected for induction of spawning should be active, free from disease, wounds

or injuries. Female fish will be in the size of 4–7 kg and males will be of 2–3 kg. Since

seabass spawning is found to have lunar periodicity, days of new moon or full moon or

one or two days prior or after these days are preferred for inducing the spawning.

Induction of Spawning

The commonly used hormones in the finfish hatcheries for induction of spawning

are:

LHRH-a - Luteinizing Hormone Releasing Hormone analogue

(Available from SIGMA CHEMICALS- USA-

ARGENT CHEMICALS)

HCG - Human Chorionic Gonadotropins (Available in


32

pharmacy, medical shops)

Ovaprim - A Glaxo Product

But in the case of seabass, a single dose LHRH-a hormone is found to be more effective

with assured result, other hormones can also be used singly or in combination and hence

always LHRHa is preferred.

Dosage of hormone

The dosage level has been standardized as LHRHa @ 60–70 µg /kg body weight for

females and 30–35 µg/ kg body weight for males. After selecting the matured males and

females, the requirement of hormone to be injected is assessed. The hormone in the vial

(normally 1 mg) is dissolved in distilled water of known volume (5 mL). Hence, each mL

will have hormone concentration of 0.2 mg, i.e. 200 µg. After taking the weight of the

brood fish, the required hormone dose is taken from the vials using a syringe.

Administration of hormone

The fish is held firmly kept over a sponge bed. To reduce the activity, the snout portion is

covered with a hood. Just below the dorsal fin above the pectoral region the syringe needle

is inserted into the muscular region and the hormone is gently administered

intramuscularly. Since the spawning normally occurs in the late evening hours 30–36 h

after the hormone administration, the hormone is injected normally in the early hours of

the day between 07.00 and 08.00 hours.

Spawning tanks

Spawning tank size depends upon the size of the fish selected. Normally 10–20 ton

capacity tanks with provision of water inlet, drainage, overflow provision and aeration is

used.

Sex Ratio

Female seabass are generally larger (more than 4 kg) and the males are smaller (in the size

of 2–3 kg). To ensure proper fertilization normally two males are introduced for one

female in the spawning tank.


33

Spawning

Fish injected with LHRH-a hormone respond for spawning after 30–36 h of injection.

Prior to spawning, swelling of the abdomen will be seen indicating the ovulation process.

Spawning normally occurs late in the evening hours 19:00–20:00 hours. At the time of

spawning, the fish will be moving very fast and a milky white frothing could be seen in

the water surface. There will be a fishy odour which can be felt few meters away. Prior to

spawning activity, the males and the female will be moving together always, the males on

the sides of the female fish. Spawning activity in seabass coincides with lunar periodicity.

During full moon or new moon days, the activity is found to be in peak. Hence, induced

spawning is done during new moon/ full moon or one or two days prior or after these days.

Seabass has high fecundity. It is a protracted intermittent spawner (releasing eggs batch by

batch). The number of eggs released in each batch depends upon the size of the fish, the

frequency of spawning etc. In one spawning the fish may release 1–3 million eggs. The

process of spawning will follow during subsequent day also. If the condition is good, both

female and male respond simultaneously resulting spontaneous natural spawning and

fertilization is effected.

Natural spawning

Asian seabass could be made to spawn spontaneously after domestication by providing

required conditions for acceleration of maturation and spawning. By manipulating

environmental conditions as that provide in the sea like, water exchange coinciding with

tidal conditions in the sea, adjusting the salinity as that of seawater, seabass could be made

to spawn. At CIBA, under a Recirculating Aquaculture System (RAS) in the FRP circular

tanks, fish kept and maintained spawn spontaneously. Hence, fish are maintained with

least stress condition and with optimal requirement and less environmental variability. The

water provided in the tank is filtered when the water passed through sand filters and the

nitrogenous waste is utilized using the biological filters.

Fertilization

Fertilization is external. In natural spawning of seabass in good maturity condition,

fertilization will be 70–90%. The size of the fertilized eggs will be around 0.75–0.80 mm.

The fertilized eggs will be floating on the surface and will be transparent. The unfertilized

eggs will be opaque and slowly sink to bottom. Due to water hardening sometime, even


34

the unfertilized eggs, for short duration will be on the sub-surface but will sink

subsequently.

Egg Collection

After spawning and fertilization, the water level in the spawning tanks can be increased

and allowed to overflow through overflow outlet. The eggs will be pushed by the water

flow. Below the overflow pipe a trough covered with bolting cloth of mesh size 150–200

µ is kept. The water with eggs is allowed to pass through. The eggs are collected in the

next bolting cloth washed and transferred to the incubation tanks.

Incubation and hatching

The eggs collected from the spawning tank are washed to remove the debris that would

have adhered to and transferred to the hatching tanks for incubation and hatching. The

hatching/ incubation tanks can be 200–250 L capacity cylindro-conical tanks. Eggs are

kept @ 100–200 nos./ L density. Continuous aeration is provided. Temperature of 27–

28°C is desirable. The eggs will hatch out in 17–18 h after fertilization undergoing

developmental stages as below:

Embryonic development Stages Duration

One Cell stage 30 minutes

Two Cell stage 40 minutes

Four Cell stage 45 minutes

Eight Cell stage 60 minutes

Thirty two Cell stage 2 hrs

Sixty four Cell stage 2 hrs 30 minutes

128 Cell stage 3 hrs

Blastula stage 5 hrs 30 minutes

Gastrula stage 6 hrs 30 minutes

Neurula stage 8 hrs


35

After hatching the larvae are transferred to larval rearing tanks. The unhatched/

unfertilized eggs (dead eggs) in the incubation tank can be removed by siphoning. The

larvae are scooped gently using scoop net and transferred into buckets of known volume.

After taking random sample counting depending upon the number required to be kept in

the rearing tanks, larvae will be transferred to rearing tanks.

Larval rearing

Larval rearing can be done in indoor and outdoor tanks. Indoor tanks are desirable since

close monitoring of feed, water quality and health is possible. The influence of extraneous

factors like light intensity, algal blooms can be avoided. Outdoor tanks are mainly

extensive type. As the larvae may grow large, the ultimate survival will be very low.

Rearing tanks can be circular or rectangular FRP or concrete tanks with proper slope on

the outer side for larval collection. Provision for clear filtered seawater, freshwater and

aeration should be made. Tanks in the size of 4–5 ton capacity are preferable for

operational convenience. Larvae can be reared in the same rearing tanks up to 25–30 days

or it can be transferred/ thinned to other tanks after 14 days depending upon the larval

density in the rearing tank. Freshly hatched healthy larvae (hatchlings) from the

incubation tanks are transferred carefully to the rearing tanks. Larvae are stocked initially

@ 40–50 nos./L. Depending upon the age and size, the larval density is reduced to 20–25

nos./L on 10th day and later, and after15 days, the density is maintained around 10–15

nos./L.

Important live feed for feeding fish larvae

Algae: Green unicellular algae like Chlorella spp., Tetraselmis spp., Nannochloropsis or

Isochrysis spp. are needed for feeding the live feed (zooplankton, rotifer) and for larval

rearing water quality maintenance.

Early embryo 11 hrs

Heart functional and tail movement 15 hrs

Hatching 17 – 18 hrs

Hatched larval size 1.4 to 1.5 mm


36

Rotifer: Rotifer (Brachionus plicatilis) or B. rotundiformis is the most preferred diet for

the fish larvae in their early stages. Size of the Rotifers varies from 50–250 μ. The early

stage larvae (up to 7 days) are fed with small sized rotifer, viz. less than 120 μ and later

assorted size can be fed.

Artemia: Artemia the brine shrimp, Artemia salina in nauplii stage is required for feeding

the larvae from 9th

day to till 21 days.

Water quality management

Water quality in the rearing tanks is very important for better survival and growth of the

larvae. Water provided to the larval rearing tanks should be free from flagellates, ciliates

and other unwanted pathogenic organisms. Water should be filtered through biological

filters, pressure sand filters. UV radiation treatment is also given to get rid of the

pathogenic organisms. If chlorine treated water is drawn, residual chlorine should be

removed, since, fish larvae are highly sensitive to chlorine and water should be used only

after dechlorination. In the larval rearing tanks, the larvae stocked as well the live feed

supplied for the larvae will excrete nitrogenous metabolites and other debris also will

accumulate. They have to be removed carefully. The debris and bottom sediment are

removed by siphoning using siphon tubes. The bottom debris is slowly siphoned out

along with water into a rough with filter net. The mesh size of the filter net used will be

100–200 μ for water change up to 9 days. After wards filter net with 200–400 μ mesh size

can be used. To maintain water quality in the larval rearing tanks, 30–40% water change

is done daily. The salinity should be maintained around 30 ppt and the desirable range of

temperature is 27–29°C. Algal water is added daily up to 15th

day. After bottom cleaning

and water reduction, while water change is done, algal water is also added depending

upon the concentration (around 20 thousand cells/ mL in the rearing tank). This algal

water play an important role is the larval rearing tank.

Feeding

Feeding larvae should be done with utmost care. Under feeding will lead to starvation and

cannibalism in seabass larvae. Excessive feeding with feed like rotifers will remain in the

tank and excrete toxic metabolites deteriorating conditions in the tank. Feed rationing and

feeding depends upon the larval density and conditions of the larvae. Rotifer (B. plicatilis)

is given as feed to the larvae from the 3rd

day. Rotifer is maintained in the larval rearing

tanks at concentration @20 nos./mL initially. From 4th

day to 15th

day, the rotifer


37

concentration is increased to 30-50 nos./mL gradually . Every day after water exchange,

the food concentration in the tank should be assessed and fresh rotifers should be added at

the required concentration. In the early stages (3–5 days) the larvae may not be in a

position to ingest the large sized rotifers. Hence, after collecting the rotifers from the

tanks, small sized rotifer less than 100 μ should be sieved using suitable mesh size bolting

cloth nets. Rotifers collected are passed through bolting cloth net of 100 μ are collected

and fed to the early larvae. From 6th

day assorted size rotifer can be given as feed.

Artemia nauplii are given as feed along with rotifers and green water from 10th

day. By

this time the larvae will be around 4 mm TL in size. Larvae can be fed exclusively with

Artemia from 16th

day to 24th

day. The density of the brine shrimp nauplii in the rearing

medium is maintained @2000 nos./L initially and gradually increased to 6000 nos./L as

the rearing days progress. From 25th

day the larvae can be fed with Artemia sub-adult

biomass or formulated feed. Under circumstances, when the rotifers could not be fed with

marine Chlorella adequately, the nutritional quality of such rotifers may be poor. In such

case, the rotifers can be enriched with special enrichment media. Enrichment is done by

keeping the rotifers in emulsified enrichment medium like SELCO DHA orcod-liveroil

for 18–24 h.

Grading

Seabass while growing exhibits differential growth, hierarchy, resulting different size

groups in the same rearing tank. Larger ones (shooters) dominate others for food and

space, and also prey on them. Seabass larvae are highly cannibalistic in early stages. In

the rearing tanks, when the larval concentration is more and congregation takes place for

food and feeding, the larger ones tempted to feed on the smaller ones. To avoid this

problem, regular grading has to be done. The large sized larvae have to be removed.

Uniform sized larvae should be kept in the rearing tanks for better survival and growth.

Grading should be done once in three days from 15th

day or whenever different size larvae

are seen in the tanks. Grading can be done using a series of fish graders with different

pore size of 2, 4, 6, 8 and 10 mm. Grading may cause injuries leading to mortality. Hence,

proper care should be taken in handling the larvae. Prophylactic treatment with 5 ppm

acriflavin may be given. After rearing the larvae in the hatchery for 25–30 days, the fry

can be transferred to nurseries for further growing.


38

3.3. Cobia, Rachycentron canadum

Cobia is considered as one of the fastest growing fishes, which can attain the weight up to

6-8 kg in a year under ideal culture conditions. Considering the commercial importance of

this fish, many countries have taken up breeding and culture of this fish worldwide. Major

cobia producers are Bahamas, Belize, the Dominican Republic, Mexico, the Philippines,

Puerto Rico, United States of America and Vietnam (FAO Report). In India, this species

is popularizing in the recent years. Some of the government institutions have taken up

seed production and culture programmes of this species in India to promote the

commercial farming.


Broodstock maintenance of cobia can be done in three holding facilities according to the

resources available with the entrepreneurs, viz. tanks, ponds and cages. Size selection,

procurement and transportation methods are few important aspects to be taken care for

injury free and healthy selection of brooders from the wild. CIBA has developed the

protocol for pond based broodstock development of cobia. Cobia fish in the size range of

5–25 kg can be maintained in earthen ponds. Water exchange up to the extent of 20–30%

can be done daily. The salinity required is above 30 ppt. Fish can be fed with forage

fishes such as tilapia/ oil sardine @ 5% body weight once daily.

Sexual maturity and spawning

Sexual maturity is reported in males at 1–2 years and in females at 2–3 years, with

females growing both larger and faster with maximum size up to 60 kg. In the nature, it is

reported that cobia spawning takes place in both near shore and off-shore waters where

females release several hundred thousand to million eggs (1.4 mm diameter) which are

then fertilized by the attending males. Under captivity, cobia can be induced to breed

through hormone application.

Induced breeding

CIBA has developed the induced breeding technique of pond reared cobia. Cobia fish in

the size range of 5–25 kg can be maintained in the earthen pond at a salinity range of 25–

30 ppt. Within one year these fish attain the maturity. Female fish with the ova diameter

of above 0.65 mm and the oozing males will be selected in the ratio of female and male

1:2 for induced breeding. For induced spawning, female fish were given a prime dose

with HCG @ 300 IU/kg body weight and the males received half of the female dose.


39

Successful spawning was observed after 36 h. Fertilized eggs are floating type, which can

be collected using suitable nets.


The fertilized floating eggs were collected and stocked in the incubation tanks @ 250–

400 nos./L with continuous flow through and aeration. After the incubation of 16–18 h,

eggs hatch out.

Larval rearing

In the larval rearing system, larvae are fed with rotifers from the 3rd

day and continued up

to 6th

day, after which they are fed with Artemia nauplii for a period of 13 days. The

larvae slowly weaned to the formulated diet from 14th

day and totally conditioned to feed

on formulated feed from 18th

day post-hatch. Over period of 30–45-days rearing, the

juvenile cobia attained total length of 10–12 cm and which will be further reared in

nursery and grow-out culture system in cages and ponds.

3.4. Grey mullet, Mugil cephalus


Adult Grey mullets to be used for breeding purposes are obtained from pond reared stocks

of over 2 years of age or collected from the wild during their spawning migrations. Adult

broodstock maintained in confined conditions in large RCC tanks or ponds are fed ad

libitum with a specially formulated pellet feed containing 32–35% protein and over 6%

lipid content.

Broodstock management

For the healthy broodstock it is essential to maintain the stocks in good quality seawater

of over 30 ppt salinity avoiding over-crowding and mishandling. Broodstocks should be

carefully observed daily for any changes in appetite or swimming behaviour. Presence of

parasites such as Caligus or poor water quality must be immediately corrected. Monthly

prophylactic bath treatment (60 min) with 100 ppm formalin is essential to keep the

ectoparasitic infections under control. At monthly intervals, captive broodstock are

examined for development of gonads. Fish are anaesthetised with 2-phenoxyethonol (300

ppm) before handling gently.


40

Sexual maturity

Adult males attain sexual maturity after 2 years while females mature during their 3rd

year

of age. Development of gonads, testes and ovary occurs during the month of August in the

East Coast of India. Oozing males can be noticed by September, while the females will be

in various stages of ovarian maturity. Maturity stage of female can be assessed by the

roundish soft abdomen, bulged pink genital opening and microscopic evaluation of the

ova obtained by catheterization (biopsy). Female mullets having large vitellogenic

oocytes measuring over 530 μ are selected for breeding induction by hormone treatments.

Female M. cephalus in captivity, although will attain maturity, could not undergo full final

maturation and ovulation. Hence, a variety of hormonal treatments are administered to

induce female mullets to ovulate and spawn in captivity.

Hormonal induction of spawning

The most effective hormonal treatment for spawning flathead grey mullet is to select a

female at the appropriate stage of maturity and employ a two-injection protocol involving

a priming injection of carp pituitary homogenate (CPH @ 10 mg/ kg) or Human

Chorionic Gonadotrophin (HCG @ 10000 IU/ kg). This is followed 24 h later with a

resolving injection of Luteinizing Hormone Releasing Hormone analogue (LHRHa @ 100

or 200 μg/ kg). Males are administered half the dose (100 μg/ kg LHRHa) at the time of

resolving dose of the female mullet. Females usually spawn 12–18 h after receiving the

resolving injection.


One hour after spawning, the spawned eggs are collected from the surface of the water by

scooping. This is done using a fine mesh net and incubated in a 500 or 1000 L incubation

tanks at density of 500 eggs/ L, with continuous aeration and flow through of clean sea

water. When the mullet embryos reach somite stage of development (about 15 h), aeration

and seawater flow in the incubation tank are turned off. Salinity of sea water should be

32–35 ppt. All fertilized eggs will float to the surface of water. Dead eggs and debris

settle to the bottom. Viable floating eggs are skimmed and transferred to larval rearing

tanks where they would hatch in about 35 h at26°C. Stocking rate of eggs in the larval

rearing tank is 25 eggs/ L.


41

Larval Rearing

In larval rearing system, larvae are fed with rotifers from the 3rd

day and continued up to

6th

day, after which they are fed with Artemia nauplii for a period of 15 days. The larvae

slowly weaned to the formulated diet from 15th

day and totally conditioned to feed on

formulated feed from 18th

day post-hatch.

3.5. Pearlspot, Etroplus suratensis

Pearlspot is an indigenous brackishwater fish belonging to the family Cichlidae, endemic

to peninsular India and Sri Lanka. Its distribution extends from Gujarat on the West Coast

to Odisha and Bengal on the East Coast of the country. This species has also been

transplanted into the inland saline water of Haryana. This is a very popular fish in Kerala

and is called “Karimeen” in Malayalam. It is also called as “Sethukendai” in Tamil,

“Cashimara” in Telugu, “Elimeenu” in Kannada and “Kalundar” in Konkani. Pearlspot is

tolerant to a wide salinity conditions. It can be cultivated in freshwater to all levels of

salinity including full strength seawater. However, it performs best at low salinities of 10–

20 ppt. It has the potential to grow to large size of up to 1 kg but the common marketable

size are smaller in the ranges of 100–250 g, fetching high price in Kerala. This fish is

omnivorous and feeds on all natural food available in the system including algae and plant

materials. It easily accepts artificial feeds and hence locally formulated feeds are adequate

for its cultivation.

Maturity and spawning

Fish attain maturity when they are over 40 g in weight. Males and females are distinct,

and can be easily identified by their colour and appearance of genital papillae. Spawning

takes place in shallow clear waters along the margins of the pond or tanks, and eggs are

laid and attached in a single row as a patch on pre-prepared substrates such as tiles,

coconut husks, flat stone. Generally, the breeding season peaks twice in a year, but if

conditions are suitable, they can breed throughout the year.

Parental care

Pearlspot exhibits elaborate breeding and spawning behaviour and the parent fish take

care of the laid eggs and hatchlings (parental care). Both parents clean and guard the egg

patch and also provide water circulation by continuous fanning with their pectoral fins.

Larvae on hatching are transferred in to small pit like depressions in the bottom soil and

are taken care. Once the larvae become free swimming they hover and swarm around the


42

parents for another 7–10 days. During this period of larval development, a major portion

of their nutrition is derived by nipping on the mucus of the parent fish.

Controlled breeding

Since this fish easily breeds in tanks and ponds, their natural breeding is facilitated by

providing substrates for egg attachments and seeds are netted out once in 15 or 30 days.

But this system is inefficient since many of the young ones get damaged due to injury and

survival is poor. Efficient systems of controlled breeding and easy seed collection

methods have been developed by CIBA for year round production of young ones.

Maximum fecundity of pearlspot has been reported as 6000 per female. But generally fish

of 150–250 g size used for breeding produce around 3000 eggs per batch.

Three systems of pearlspot seed production has been standardized at CIBA

a) Earthen pond breeding system

b) RCC tank breeding system

c) Hapa or net cage breeding system

Earthen pond breeding system

In the pond breeding system, 500 adult pearlspot of 150–250 g size are stocked in an

earthen pond of around 900 to 1000 m2 area. Fish are fed mash feed in dough form or

formulated pellet feed at 2% of total biomass. Palm leaves are placed at several points for

egg attachment. Pair formation, breeding and egg attachment occurs naturally. If no

breeding takes place, the fish can be induced by reduction in water salinities. Once a

month, fry collection can be done using a small meshed net around bunches of twigs

placed at several places for aggregating the fish seed.

RCC tank breeding system

Breeding in RCC tanks is done by stocking 20 adult pearlspot of over 150 g size at male

and female ratio of 4:6 in a 20 ton tank. Before release of breeders, tank is provided with

about four inches of soil at the bottom and 10 tiles are suspended for egg attachment.

Water with salinity around 20 ppt is allowed to flow-through and feeding is provided ad

libitum in feeding trays. The tiles are checked frequently for egg deposition. Tiles with

attached eggs can be carefully shifted to a separate hatching tank or if hatching occurs in

the breeding tank itself, the hatchlings can be carefully collected from the larval pits, for

rearing separately. From each batch 700 to 2100 fry can generally be obtained.


43

Hapa or net cage breeding system

In hapa breeding system, 2–4 adult pearlspot are released into a fine meshed hapa of

1.5×1×1 m dimension. A tub with little soil and an earthen tile are suspended inside the

hapa. Breeding and hatching occur in the larval pit or inside the tub, and the larval stages

(wrigglers) can be collected for rearing.

Recirculation system

Breeding trials of pearlspot were conducted in 1 ton rectangular plastic tanks provided

with a continuous water flow using a biofilter facility. Each tank was provided with a small

plastic tub filled with clayey soil to facilitate breeding. Each breeding tank was stocked

with 4 mature brooders (total length >160 mm) and fed with pellet feed twice a day @ 2–

3% body weight. Pairing in the tanks could be observed within 2–3 days of stocking and

the paired fish were observed to occupy the soil filled plastic container provided.

Aggressive behaviour was observed to centre on this container and the breeding pair was

seen to actively chase other approaching fish from it. The aggressive behaviour increased

towards approach of breeding, even leading to mortality.

Pearlspot larval rearing

The wrigglers are reared in small FRP tanks of 50–100 L capacity. Larvae will be

exhibiting as warming behaviour after the yolk is absorbed and will have to be fed with

rotifers, and later with Artemia nauplii. Fry can be fed with formulated particulate feed or

moist feeds like egg custard, twice daily. Fry are prone to parasitic infections which can

be taken care by prophylactic formalin bath at 50 ppm for 30 min.

3.6. Breeding of milkfish, Chanos chanos

Milkfish ChanosChanos is an important brackishwater candidate species suitable for

brackishwater farming. Being herbivore, it can feed low protein feed which is of low cost

and there by production cost can be reduced. It is an ideal species for polyculture farmed

along with mullet and shrimp species. Farming of milkfish in India is at primitive stage

since the seed is mainly collected from the wild source. During the months from March to

May, larval or fry size seed are collected abundantly along the east coast of India

especially in Andhra Pradesh and Tamil Nadu coasts. These seeds are collected by the

local fishermen along with other fishes and sold to farmers. Farmers stock these seed

directly in the ponds without segregation of the predatory fishes. Milkfish can reach to


44

500 g size in six months culture period under brackishwater pond condition. The

production cost would be around Rs.60–70/kg. In the domestic market, milkfish can be

sold @ Rs.100–150/kg.

Selection of brooder

Milkfish seed production technology has been well documented in Philippines, Indonesia

and Taiwan. It is reported that mature male female collected form wild or reared under

captive condition is used for breeding.

Induced Spawning

Vanstone et al. (2015) induced to spawn milk fish with acetone dried pituitary gland

extract and HCG. Other inducing agents such as GnRH can also be used to induce the

maturation and spawning.

Egg Incubation

Embryonic development which was very similar to that described for other pelagic fish

egg (Vanstone et al., 2015). Egg sizes ranged from 1.1 to 1.23 mm, with a mean diameter

of 1.16 (Vanstone et al., 2015).The yolk was slightly yellowish, devoid of oil globules

and finely granulated. The egg at this stage was buoyant in water of 34 ppt salinity and

hatching occurred 35 to 36 hr afterward. Incubation required mild aeration to keep eggs

floating.Like othe marine fish eggs dead eggs will settled at the bottom of the incubation

tanks which need to siphoned out. Newly hatched larvae measured 3.5 mm in total length

(Vanstone et al., 2015).

Larval rearing

It is documented that the yolk was completely absorbed in 3-day old larvae) which also

measured 5.1 mm (preserved. The larvae were fed various mixtures: 1) Chlorella with

contaminating diatoms and protozoa, 2) immature Brachionu splicatilis (40–60 µ), and 3)

mixed zooplankton between 40 to 60 µ in size which were collected by means of an airlift

pump (Novotny, 1971) from the lagoon adjacent to the laboratory. During larval rearing

in the aquaria, the salinity ranged from 32 to 34 ppt and the temperature from 27.5 to

29.7°C (Vanstome et al., 2015).

3.7. Breeding of brackishwater cat fish, Mystus gulio

Mystus gulio, locally known as Nona Tengra in West Bengal and Bangladesh is a catfish

belonging to the order Siluriformes and family Bagridae. They are commonly found in


45

coastal waters of Bangladesh and eastern coast of India. Considering the euryhaline

nature, this fish has potential for culture in both brackishwater as well as freshwater ponds.


Adult brood fish were collected from wild, quarantined and stocked in 500 L tanks. Fish

were fed with chicken liver or trash fish enriched with vitamin E daily twice @ 3% body

weight. At regular interval oocytes development was observed through cannulation. Fish

were implanted with hormone implant to accelerate maturation process in captive

condition.

Induced breeding

Mature male and female in the ratio of 2:1 were selected for induced breeding.

Primary dose: Selected males and females were injected either with HCG or pituitary

gland extract or LHRH implant as per body weight of the fish.

Secondary dose: After 36 h males and females were injected with HCG or LHRH at the

same dose.


Fertilized eggs (transparent and sticky in nature) were collected and incubated for 18 h.

Hatchlings were fed with egg custard from 3 days onwards and later on weaned to Artemia

nauplii.


46

Sustainable Brackishwater Aquaculture Practices

Gouranga Biswas, Prem Kumar, S.N. Sethi* and Aritra Bera*



4.1. Introduction

Aquaculture is now the fastest growing food production sector in different regions of the

world except Sub-Saharan Africa. In land based and offshore culture systems, 210 species

of finfish, molluscs, crustacean and sea weeds are farmed, yielding about 90 million tons

annually and accounting > 50% of the world‟s fish supply for direct human consumption.

It is forecasted that 62% of food fish will come from aquaculture by 2030. In India,

sufficient protein rich food or food products must be available for her population sharing

>17% of the world population. Thus, aquaculture has emerged as a highly vibrant sector

worldwide. The global average per capita consumption of fish is around 15 kg. The

present average per capita consumption in India is around 9 kg. Even in countries like

Japan and some of the South East Asian countries the average per capita consumption is

more than 100 kg. To reach the global average of 15 kg, taking into consideration of 50%

of Indian population will be fish consumers; by 2020 the domestic requirement itself will

be in the order of 9 million tons. The average fish production in India is around 9 million

tons equally contributed by freshwater and marine sectors. The maximum sustainable

yield is static and the capture fisheries trend is declining. It is expected that the

brackishwater aquaculture has to make a greater contribution to the fish production in

Indian context. By 2020, the coastal aquaculture is expected to support to the tune of

around 3,50,000 tons, from the current production of around 1,50,000 tons. This implies

that a quantum jump has to be made in the ensuing years. Out of this, shrimp is expected

to contribute around 2,50,000 tons and rest has to come through fishes and other non-

conventional groups.

4.2. Resources for brackishwtaer aquaculture

The scope for increasing the fish production through aquaculture is great. Along the 8118

km of the coastline of India, intercepted with innumerable estuaries, creeks, backwaters

lagoons and lakes it is extended to a potential area of 1.20 million ha for brackishwater

4


47

farming. Apart from this, in the upland inland area a vast stretch (8.5–9.0 million ha) of

saline ground and surface water exists, which can only be used for salt water fishes.

Table 1. State-wise estimated potential brackishwater area and area under shrimp culture.

State Estimated potential

area (ha)

Area under shrimp

culture (ha)

Andhra Pradesh 150,000 39,750

West Bengal 405,000 49,174

Kerala 65,000 13,236

Orissa 31,600 7,732

Tamil Nadu &

Pondicherry

56,800

5072

Karnataka 8,000 812

Goa 18,500 34

Gujarat 376,000 4426

Maharashtra 80,000 1401

Total 1,190,900 1,21,637

Source: MPDEA 2014-15

4.3. Status of brackishwater aquaculture

Coastal aquaculture is a traditional practice in India. In the low-lying fields of Kerala

(Pokkali), West Bengal (Bheries), Odisha (Gheries), Goa (Khazans) and Karnataka

(Kharlands) which experience influx of saline water, traditional farming of fish/shrimp

has been practiced. The practice includes allowing entry of juveniles of fish/shrimp in the

fields and letting them to grow, applying supplementary feeding sometimes, facilitating

tidal water exchange and harvesting periodically at 3–4 months. With the improvement of

technologies and realizing the importance of aquaculture, these practices were improved

with the supplementary stocking and water quality management resulting in moderate to

higher production. The technology improvement made in the aquaculture sector has

opened new areas for the scientific farming which is called as semi-intensive and intensive


48

farming following all the protocols for farming with production as high as 10 ton/ha per

culture period of 4–5 months for mainly shrimp and brackishwater fish like seabass

production of 3 to 4 ton/ha/crop in the coastal area. Polyculture of fish and shrimp with

different stocking patterns has yielded a productivity of 3 ton/ha/crop in South 24

Paraganas of West Bengal. In addition to that farmers have achieved a production of 2

ton/ha/crop of milkfish when it is practiced in monoculture system in West Bengal and in

Andhra Pradesh. Green water technology in brackishwater aquaculture has been

standardized and farmers started adopting the same in different costal districts of Tamil

Nadu. Phenomenal growth in Pacific whiteleg shrimp, Litopenaeus vannamei farming has

been occurred in the recent past. The technology advancement helped in the establishment

of more than 390 shrimp and 1 crab hatcheries. The coastal aquaculture witnessed a rapid

growth during 1980s and in the beginning of 1990s. But the shrimp aquaculture sector

witnessed severe setbacks from the later part of 1990s due to socio-economic,

environmental issues coupled with the outbreaks of uncontrollable diseases like white spot

syndrome virus (WSSV), Monodon slow growth syndrome, loose shell syndrome, early

mortality syndrome diseases etc. The major reasons attributed to this are the unregulated

development and unforeseen disease outbreaks. The sole dependency on single species

tiger shrimp, Penaeus monodon in coastal aquaculture has been switching to L. vannamei

farming since last few years and this had pronounced impact on the coastal aquaculture

sector questioning its sustainability.

4.4. Species diversification: an advanced option for sustainable brackishwater

aquaculture

The estimated potential area under coastal aquaculture is 1.2 million ha, of which only

around 10% area has been brought under the culture. Considering the production potential

of the sector, its production is projected to grow by four-fold by 2020 from the present at

0.15 million tons. Development of Indian coastal aquaculture in the country was driven by

the technologies for seed production of tiger shrimp, P. monodon and the white shrimp,

Fenneropenaeus indicus. Disease outbreaks due to WSSV during the last 10–16 years

have acutely affected shrimp farming in the country and in other continents. With the

diagnostic kits developed for detecting WSSV, PCR-tested seed is available all over the

country. Supplementary feeding is the most important management measure in

commercial shrimp farming. Commercial shrimp farming in India largely involves use of

formulated pellet feed, constituting a significant share of the input expenditure. While bulk


49

of the feed used was imported from Southeast Asian countries till a decade back, it is at

present mainly produced in the country. Unavailability of quality ingredients, especially

the fish meal, has been a major constraint faced by these industries, requiring import. The

high price of the commercial feed, however, is forcing the small-scale farmers to resort to

farm-made feeds. For the sustainable eco-friendly aquaculture practice, diversification to

other species is considered as one of the important steps. Fishes like Asian seabass (Lates

calcarifer), grouper (Epinephelus tauvina), snappers (Lutjanus spp.), which are high value

carnivorous fishes and grey mullet (Mugil cephalus), milk fish (Chanos chanos), pearlspot

(Etroplus suratensis), rabbit fish (Siganus spp.), orange chromide (Etroplus maculatus)

which are herbivorous/omnivorous suitable for farming in the coastal eco-system are

available. The species like cobia (Rachycentron canadum), silver pomfret (Pampus

argenteus) and pampano (Trachinotus carolinus) are being considered as candidate

species for farming. Efforts have been made to develop comprehensive technology

packages for seed production under controlled conditions and farming of these candidate

species. Technologies have been developed elsewhere in the world for several

brackishwater and marine finfishes. In Indian scenario, the successful technology has been

developed for the year round seed production of Asian seabass, L. calcarifer under

controlled conditions and farming by the Central Institute of Brackishwater Aquaculture.

The institute has also accomplished controlled breeding of grouper, E. tauvina, milkfish,

C. chanos and pearlspot, E. suratensis. In addition, a new avenue has been made by the

successful breeding and seed production of ornamental fishes, spotted scat, Scatophagus

argus, crescent perch (Terapon jarbua) and orange chromide, E. maculatus. Marine sea

weeds have been a new area for brackishwtaer farming in different costal states of India.

Successful demonstration of seabass farming has been conducted in all the coastal states.

High export prices of crabs have made fattening of species like Scylla serrata and S.

olivacea as a remunerative farming practice.

4.5. Technological advances in sustainable brackishwater aquaculture practices

4.5.1. Seed rearing of finfishes

4.5.1.1. Nursery rearing of seabass

4.5.1.1.1. Nursery rearing in hatcheries

Seabass fry of 25–30 days old of 1.0–1.5 cm size can be stocked in 5–10 ton capacity

circular or rectangular (RCC or FRP) nursery tanks. Outdoor tanks are preferable. The


50

tanks should be fitted with inlets and outlets. Flow-through provision is desirable. In situ

biological filter outside the rearing tanks would help in the maintenance of water quality.

The water level in the rearing tanks should be 70–80 cm. Tanks should be provided with

good aeration facility. After filling with 30–40 cm water and fertilized with ammonium

sulphate, urea and superphosphate @ 50, 5 and 5 g (10:1:1 ratio) per 10 ton of water,

respectively. The natural algal growth would appear within 2–4 days. In these tanks,

freshly hatched Artemia nauplii @ 500–1000 nos./L are stocked after leveling the water to

70–80 cm. The nauplii stocked are allowed to grow into biomass feeding with rice bran.

When sufficient Artemia biomass is seen, seabass fry are stocked @ 800–1000 nos./m3.

The pre-adult Artemia would form good food for seabass fry. The fry would not suffer for

want of food in the transitional nursery phase in the tank since the larvae are habituated to

feed on Artemia in the larval rearing phase. Along with „Artemia biomass‟ available as

feed inside the tank supplementary feed mainly minced fish/shrimp meat is passed through

a mesh net to make each particle of size of around 3–5 mm and cladoceran like Moina sp.

can also be given. The fish/shrimp meat feeding has to be done 3–4 times daily. Feeding

rate is 100% of the body weight in the first week of rearing. This is gradually reduced to

80, 60, 40 and 20% during 2nd

, 3rd

, 4th

and 5th

week, respectively. Regular water change to

an extent of 70% is to be done daily. The left over feed and the metabolites have to be

removed daily and aeration should be provided. In a rearing period of 4–5 weeks in the

nursery rearing, the seed will be in the size of 1.5 to 3.0 g/ 4–6 cm with survival rate of

60–70%. Adopting this technique at a stocking density @ 1000 nos./m3 in the hatchery,

survival rate up to 80% has been achieved. For better survival „grading‟ should be done

regularly. Vessels/ troughs placed with different mesh sized nets can be used for grading.

When the seeds are left into the containers the seeds will be sieved in different grades

according to the mesh size and seed size. Care should be taken that the fry are not injured

while handling. If the number is less it could be manually done.

4.5.1.1.2. Nursery rearing in grow-out site

Rearing fry to stockable size seed in the hatchery itself has some problems. All hatcheries

may not have such facilities since the requirement of space will be 5–6 times more than

larval rearing space. Maintenance requires additional man power, energy etc. Above all,

transportation of large sized seed to culture site would be expensive. To avoid these

problems nursery rearing in grow-out site itself can be done wherever possible.


51

4.5.1.1.2.1. Nursery rearing in ponds

Nursery ponds can be around 200–500 m2 area with provision to retain at least 70–80 cm

water level. Adequate provision for water inlet and water drainage should be provided.

Towards drainage side there should be slope. Suitable sized (normally 1 mm) mesh screen

nets should be provided in the inlet side and outlet side to avoid entry of unwanted fishes

and escape of the stocked fish, respectively. The pond is prepared before stocking. If there

are any predator/pest fishes they have to be removed. In case where complete draining is

not possible, water level is reduced to the extent possible and treated with Derris root

powder @ 20 kg/ha or mohua oil cake @ 2000–3000 kg/ha-m to eradicate unwanted

fishes. Use of other inorganic chemicals or pesticides is avoided because these may have

residual effects. After checking the pond bottom quality water is filled. If the pond bottom

is acidic, neutralization is done with lime application. In order to make the natural food

abundant, the pond is fertilized with chicken manure @ 500 kg/ha keeping the pond water

level 40–50 cm. The water level is gradually increased. After 2–3 weeks period when the

natural algal food is more, freshly hatched Artemia nauplii are introduced. Normally 1 kg

of cyst is used for 1 ha pond. These stocked nauplii grow and become biomass in the pond

forming food for the seabass fry.

Seabass fry is stocked @ 20–30 nos./m2. Stocking should be done in the early

hours of the day. Fry should be acclimatized to the pond condition. Acclimatization for the

pond condition is done as follows: the fry in the transport container are emptied into

another tank and the pond water is gradually added into the container. This process is

continued for a day or two depending upon the difference in the parameters. When the

water temperature and salinity in the pond and tank water reach same, fry can be released

into the pond. Water is changed @ 30% daily. Supplementary feeding is done with

chopped, cooked fish/shrimp meat. The larvae can be weaned to artificial feed at this

stage. The feeding rate can be as mentioned earlier. Excessive feeding should be avoided

since it would deteriorate the pond condition and also promote filamentous algal growth.

The excessive algal growth would deplete dissolved oxygen level in the early hours of the

day leading to fish mortality. Hence, excessive algae if any should be removed.

4.5.1.1.2.2. Nursery rearing in cages/ hapas

This method is advantageous to other methods since the management is easier and

installation of rearing facility requires less space and capital investment. It can also be


52

extended to any scale depending on the necessity and the capability of the farmer. It can be

maintained in one corner of the grow-out pond or near the grow-out cage itself. Since

cages or hapas are in in situ condition, this will provide conducive environmental

condition. The water flow in the cage site would give the fish natural condition.

Metabolites and excess uneaten feed will be washed away by the flow of water.

Floating net cages/hapas can be in the size of 211 to 221 m depending

upon necessity. Cages are made with nylon/polyethylene webbings with mesh size of <1

mm. Fry can be stocked @ 400–500 nos./m3. The net cages have to be checked daily for

damages, those may be caused by other animals like crabs. The net cages will be clogged

by the adherence of suspended and detritus materials and siltation or due to fouler

resulting in the restriction of water flow. This would create confinement in the cages and

unhealthy conditions. To avoid this, cages/hapas should be cleaned once in a or two-days.

Regular grading should be done to avoid cannibalism and increase the survival rate. Even

in higher stocking density @ 500 nos./m3 farmer could get survival of 80% in the farm site

when the fry were reared in hapas adopting the trash fish feeding and other management

strategies mentioned above.

4.5.1.2. Nursery rearing of grey mullet

Nursery rearing of wild collected stripped grey mullet fry can be conducted in

brackishwater tide-fed ponds for production of advanced fingerlings. Grey mullet fry

(0.17g/ 23.77mm) were stocked in ponds at 7500 and 15,000 nos./ha and reared for 6

months. In feed system, low cost feed prepared from locally available ingredients was

provided in powder form for initial 4 months @20-5% and in pellet form for the rest 2

months @5-3.5% body weight daily in feed trays. In fertilization system, ponds were

fertilized with cattle dung, urea and single super phosphate @ 500, 30 and 30 kg/ha,

respectively at fortnightly applications. After 180 days of rearing, fish in fertilization

system, achieved higher growth and survival than feed system.

In the previous trial a stocking density of 15,000 nos./ha was found as the optimum

density for advanced grey mullet fingerlings rearing. With this density, the effect of

fertilization and feeding was evaluated. (i) With only fertilization: Fertilization of the

ponds with cattle dung, urea and single super phosphate. Initial application was done

seven days prior to fish stocking and intermittent application was continued at 15 days

intervals; (ii) Feed alone: Low cost formulated feed in powder form for first 1 month, then


53

as pellet form for next 4 months given in feed trays. Feed was composed of rice bran,

mustard oil cake, wheat flour, fish meal and vit.-min mixture with 27%CP and 6% lipid;

(iii) Feed and fertilization: Combination of both as given under (i) and (ii). The rearing

duration was 150 days and initial larval size of 0.55 g (36.03 mm). Feed and fertilization

was found to be the best rearing system in term of final bodyweight. Though the survival

was higher in the treatment with feed and fertilization, the difference with other treatments

was not statistically significant. For the rearing systems of fertilization alone, feed alone,

and feed and fertilization, the cost of production averaged Rs.92300, 106250 and 128300/

ha, respectively with the highest net return of Rs.93400/ ha from the later method.

4.5.2. Grow-out systems (pond based)

4.5.2.1. Traditional grow-out practices

Seabass is cultured in ponds traditionally as an extensive type culture throughout the areas

in the Indo-pacific region where seabass is distributed. Low-lying excavated ponds are

stocked whenever the seabass juveniles are available in the wild seed collection centers

(For e.g. April-June in West Bengal, May-August in Andhra Pradesh, Sept-Nov in Tamil

Nadu, May-July in Kerala and June-July in Maharashtra). Juveniles of assorted size

seabass are collected and introduced into the traditional ponds which will be already with

some species of fish, shrimps and prawns. These ponds will have the water source from

adjoining brackishwater or freshwater canals, or from monsoon flood. The juvenile

seabass introduced in the pond will prey upon the available fish or shrimp juveniles as

much as available and grow. Since seabass by nature is a species with differential growth,

on introduction into the pond at times of food scarcity, the larger may resort to feed upon

the smaller ones reducing the number. Seabass are allowed to grow for 6–7 months of

culture period till such time water level is available in these ponds and then harvested. At

the time of harvesting there will be large fish of 4 to 5 kg as well as very small fish. In this

manner, production up to 2 ton/ha/7–8 months has been obtained depending upon the

number and size of the fish entered/introduced into the pond and the feed available in the

pond.

However, this practice is highly unorganized and without any guarantee on

production or return for the aquaculturists. With advances in the technology in the

production of seed under captivity assuring the supply of uniform sized seed for stocking

and quality feed for feeding, the seabass culture is done in South East Asian countries and


54

Australia in more organized manner. The major problem in the development of seabass

aquaculture in India is the unavailability of seed in adequate quantity and in time and

quality feed for nursery rearing and grow-out culture. The former has been overcome and

the technology package for the seed production of seabass under controlled conditions is

available. The suitable feed for the culture of seabass has been developed. The seed

production technology developed by CIBA has already been commercialized and the feed

technology (CIBA Bhetki AHAAR) is ready for commercialization. These technological

improvements in the seabass culture have motivated the farmers to select seabass as a

candidate species for aquaculture. Farmers have been adopting improved farming practices

in seabass culture.

4.5.2.2. Improved seabass grow-out practices

The traditional culture method is improved with stocking of uniform sized seed at specific

density and fed with low cost trash fishes/formulated feed of required quantity. Water

quality is maintained with exchange periodically. Fish are allowed to grow to marketable

size, harvested and marketed for high unit price. Seabass culture can be done in a more

organized manner as a small-scale/large scale aquaculture in brackishwater and freshwater

pond cages. This practice was further demonstrated in Public Private Partnership mode in

three different costal states of India. Successful crops have been demonstrated in Andhra

Pradesh, Tamil Nadu and Maharashtra.

4.5.2.3. Monoculture of grey mullet, Mugil cephalus

Grey mullet can be farmed in monoculture ponds. The pond for monoculture is prepared

first, following eradication of unwanted organisms and application of manures and

fertilizers. Advanced fingerlings of >50 g size are stocked at 10,000 nos./ha. Fish are fed

with supplementary feed. In an 8-month culture, fish become 500–800 g with total

production of 3–4 ton/ha.

4.5.2.4. Monoculture of milk fish, Chanos chanos

Milk fish can be farmed in monoculture and polyculture ponds. The wild seeds are

collected in organized manner in Tamil Nadu and seeds are stocked in farms in costal

ponds. The milkfish farming follows a protocol of nursery rearing and farmed with farm

made feed and floating pellet available in the market for other species. The scientific water

quality management and supplementary feeding have given a production of 2 to 2.5 ton in

West Bengal and a higher production has been achieved in Andhra Pradesh.


55

4.5.2.5. Polyculture of fishes and shrimps

Polyculture is a farming practice where two or more species of fishes are reared together.

The concept of polyculture is based on the fact that rearing of two or more compatible

aquatic species together will result in higher production compared to monoculture. The

underlying goal of polyculture involves increasing productivity by more efficiently

utilizing ecological resources within an aquatic environment. Sometimes, one species

enhances food availability to other species and thus increases total fish production per unit

area. It is commonly believed that polyculture gives higher production than monoculture

in extensive and semi-intensive systems and is considered more ecologically sound than

monoculture. Before stocking of seeds, pond is prepared well following eradication of pest

and predatory fishes, removal of bottom mud and liming, fertilization etc. The ready ponds

are stocked with seeds of fish species at 8000–15,000 nos./ha along with tiger shrimp

seeds of 15,000–30,000 nos./ha. The stocking density varies with the quantum of seed

availability. Natural pond productivity is maintained by fertilization. In addition,

supplementary feed prepared from locally available ingredients can be used at 2-5% body

weight daily. This kind of system can yield a total production of 1.5–3.0 ton/ha in 6–10

months. The preferred species among fishes are: Mullets- Mugil cephalus (striped grey

mullet), Liza tade (tade grey mullet), L. parsia (goldspot mullet), Milkfish- Chanos

chanos, Pearlspot- Etroplus suratensis and Tiger shrimp- Penaeus monodon.

4.5.2.6. Integrated multi-trophic aquaculture (IMTA)/ Brackishwater integrated

farming systems (BIFS)

IMTA is a farming practice which combines cultivation of fed aquaculture species (e.g.,

finfish/shrimp) with organic extractive aquaculture species (e.g., shellfish/herbivorous

fish) and inorganic extractive aquaculture species (e.g., seaweed/ seagrass) in the

appropriate proportions to create balanced systems for environmental sustainability,

economic stability and social acceptability. The IMTA concept is very flexible and can be

land-based (pond/RAS) or open-water systems (cage/pen), brackishwater or marine

system. IMTA is well recognized as a mitigation approach against the excess nutrients/

organic matter generated by intensive aquaculture activities especially in brackishwaters,

since it incorporates species from different trophic positions or nutritional levels in the

same systems. In addition, it is also relevant to implementation of the Ecosystem

Approach to Aquaculture (EAA) that is propagated and conceptualized by FAO.

Sometimes the more general term „integrated aquaculture‟ is used to describe IMTA. The


56

terms „IMTA‟ and „integrated aquaculture‟ differ primarily in their degree of

descriptiveness. Different forms of IMTA are Aquaponics, fractionated aquaculture,

integrated agriculture-aquaculture systems, integrated peri-urban aquaculture systems and

integrated fisheries-aquaculture systems.

Currently, the existing major IMTA systems in the world are generally simplified

with finfish, shellfish and seaweed. The aim is to increase long term sustainability and

profitability for the cultivation unit, as the waste of one crop is converted into fertilizer,

food and energy for the other crops, which can in turn be sold in market. It reduces

adverse impacts on environment while producing economically viable products at the

same time. The preferred species for brackishwater IMTA (BIMTA) are: finfishes-

seabass, milkfish and mullets; shellfish- green mussel/ oyster; seaweed- Laminaria sp.,

Gracillaria sp. or Kappaphycus sp. IMTA as viable option to fish farmers in coastal

waters in India has not been demonstrated still now. Understanding its potentiality and

sustainable nature, all the stakeholders of coastal and marine aquaculture should be

encouraged to promote it.

4.5.3. Grow-out systems (cage based)

4.5.3.1. Cage culture of seabass

Fish culture in cages has been identified as one of the eco-friendly at the same time

intensive culture practices for increasing fish production. Cages can be installed in an open

sea or in coastal area. The open sea cage is yet to be developed in many countries where

seabass is cultured but coastal cage culture is an established household activity in the

South East Asian countries. There are abundant potential in India also for cage culture in

the lagoons, protected coastal areas, estuaries and creeks. Since cage culture of seabass has

been proved to be a technically feasible and viable proposition, this can be taken up in a

large scale in suitable areas.

Cage culture system allows high stocking density and assures high survival rate. It

is natural and eco-friendly and can be adopted to any scale. Feeding can be controlled and

cages can be easily managed. Harvesting is not expensive. Even in areas, where the

topography of the bottom is unsuitable for pond construction, cage can be installed.

Diseases can be easily monitored. Fish in cages can be harvested as per the requirement of

the consumers, which will fetch high unit price. Above all, cage culture has got low capital

input and operating costs are minimal. Cages can be relocated whenever necessary to


57

avoid any unfavorable condition. In India, Rajiv Gandhi Centre for Aquaculture has

successfully demonstrated the pond based cage farming of seabass.

4.5.3.1.1. Stocking density

In the cages, fish can be stocked @25–30nos./m3 initially when they are in the size of 10–

15 g. As they grow, after 2–3 months culture, when they are around 100–150 g, density

has to be reduced to 10–12 nos./m3 for space. Cage culture is normally done in two

phases- till they attain 100–150 g size in 2–3 months and afterwards till they attain 600–

800 g in 5 months.

4.5.3.1.2. Feeding in cages

Fish in the cage can be fed with either extruded pellets or with low cost fishes as per the

availability and cost. Floating pellets have advantages of procurement, storage and

feeding. Huge quantity of low cost fishes are landed in the commercial landings in the

coastal areas which fetch around Rs.5–10/kg only and can be used as feed for seabass

culture. Low cost fish like tilapia available in freshwater and brackishwater also serves as

feed for seabass in ponds and in many cage culture operations. The rate of feeding can be

maintained around 20% initially and reduced to 10% and 5% gradually in the case of trash

fish feeding and in the pellet feeding, the feeding rate can be around 5% initially and

gradually reduced to 2–3% at later stage. In the feeding of low cost fish, FCR works out

around 6 or 7 (i.e., 7 kg of cheaper fishes has to be given for one kg of seabass). In the

case of pellet feeding, FCR is claimed to be around 1 to 1.2 in Australia. However, the

cost effectiveness of the pellet feeding for seabass in grow-out culture has to be tested.

4.5.3.1.3. Production

Under cage culture, since seabass can be intensively stocked and properly managed, the

production will be high. Frequently culling and maintenance of uniform sized fish in the

cages will ensure uniform growth and high production. Production of 6–8 kg/m3 is

possible in the cages, under normal maintenance and production as high as 20–25 kg/m3 is

obtained in intensive cage management in the culture of seabass.

4.5.3.2. Integration of cage culture of seabass with shrimp culture

If seabass can be weaned to feed on floating pellets, because of their addictive nature to

selective feed, they will not resort to prey upon shrimp as normally experienced in shrimp

culture ponds. If the water depth can be maintained around 1.5–2.0 m, in a pond, cages can


58

be installed in the shrimp culture pond itself and seabass seed weaned to feed on floating

pellets can be stocked in the cages and reared. In this way, seabass culture will be a

complimentary to shrimp culture.

4.6. Challenges in advancement of brackishwtaer fish culture

The barckishwater aquaculture production potential is not utilized due to several

constraints. Few of them are highlighted below.

Poor infrastructure for farming system in different costal states.

Unavailability of quality seed as input for finfish culture.

Improved nursery rearing technology for other finfishes.

Larval and broodstock diet for commercial hatchery operation.

Poor health management facilities and disease outbreak.

Unavailability of uniform leasing policy of land for brackishwater aquaculture in

different costal states.

Poor market intelligence and facilities for marketing of harvested product.

Poor post-harvest technology.

Lack of awareness about the new finfishes.

4.7. Future strategies towards attaining sustainabilty

The attempt to improve the production from brackishwater aquaculture should focus on

following strategies, which will address the above challenges.

Hatchery and seed production technology for finfishes like grey mullets, cobia,

pampano, snapper etc.

Breed improvement and diversification with finfishes such as seabass, mullets,

pearlspot and cobia.

Establishment of aquatic quarantine and biosecurity system, with suitable capacity

building at various levels.

Availability of quality and affordable feed for farming of different species.

Comprehensive health management with disease diagnostics and treatment

measures for broodfish and larvae.


59

Water budgeting and management in aquaculture practices, including treatment

and use of wastewater, recycling and multiple use of water and mechanisation in

aquaculture.

Integrated farming systems for enhancing input use efficiency.

Brackishwater ornamental fisheries as an enterprise.

Comprehensive national policy for brackishwater aquaculture.

Establishment of model hygienic domestic markets and improvements in fish

distribution system with reduced number of intermediaries in market channels and

door to door delivery of fish/fish products.

Emphasis on infrastructure development for aquafarming site.

Market information and training on marketing intelligence, with a national data

centre for exports of fish products.

Ensuring food safety through necessary laboratories and trained personnel.

Rapid detection of pathogens and contaminants in fish products.

Insurance system for all fishery based commercial activities right from producers

to user‟s level.

Ensuring financial assistance for fisheries and aquaculture activities from

production to consumption level.

4.8. Capacity building

Different capacity building steps are: strengthening extension mechanisms and use of

information and communication technology (ICT) for educating farmers on new

technologies including exposure visits, capacity building in State Fisheries Departments

and capsule courses in local language about fish culture for aquafarmers through Matsya

Pathshalas, setting up of Aqua Service Centres, model fish farms and laboratories for

soil-water testing and disease diagnosis, community-based fisheries entrepreneurship

training for women like brackishwater ornamental fish production, post-harvest

technology etc.


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4.9. Conclusion

The aquaculture development project should try to achieve the maximum possible yield,

which is not currently possible with existing technology and infrastructure. Development

of eco-friendly and cost-effective culture technologies of finfish targeting small-scale

farmers is the need of the hour. Some steps towards brackishwater aquaculture

development are extension of culture to inland saline areas, bringing more areas under

culture, species diversification from existing shrimp to fishes etc. Adequate availability of

quality fish seeds will also help in expansion of culture.


61

Shrimp Farming with Special Reference to

Litopenaeus vannamei Culture

Christina L. and P.S. Shyne Anand*


*ICAR- Central Institute of Brackishwater Aquaculture, Chennai

5.1. Introduction

Shrimp farming has always been a major centre of brackishwater aquaculture in India.

Major candidate species include Penaeus monodon, Penaeus semisulcatus,

Fenneropenaeus indicus, Fenneropenaeus merguensis, Fenneropenaeus penicillatus,

Metapenaeus monoceros, Metapenaeus kutchensis, Metapenaeus dobsoni and

Metapenaeus brevicornis. Initially, shrimp aquaculture in India in its predominant form

was essentially farming of Penaeus monodon. The importance of shrimp farming to

country‟s economy was realized in the early seventies and the first experimental

brackishwater fish farm was started in Kakdwip, West Bengal by Central Inland Fisheries

Research Institute (CIFRI) under Indian Council of Agricultural Research in 1973 and All

India Co-ordinated Research Project on Brackishwater Fish Farming was started in 1975

by ICAR with centres in West Bengal, Orissa, Andhra Pradesh, Tamil Nadu, Kerela and

Goa. The growth rate of the black tiger shrimp farming was phenomenal until the first

outbreak of White Spot Syndrome Virus (WSSV) in 1995 and subsequently viral infection

plagued the shrimp farming sector of the country.

In 2003, considering the commercial success of specific pathogen free (SPF)

Litopenaeus vannamei culture in some of the South East Asian countries, the National

Committee on Introduction of Exotic Species in Indian waters under the Ministry of

Agriculture approved the proposal to take up the culture operation of this exotic species

on an experimental bases under controlled bio-secured conditions. At present, farming of

L. vannamei is allowed only in hatcheries and farms that are registered with Coastal

Aquaculture Authority (CAA).

5.2. Shrimp production and trade

According to FAO Statistics (2014), in 2012, farmed crustaceans accounted for 9.7% (6.4

million ton) of food fish aquaculture production by volume and 22.4% (US$30.9 billion)

5


62

by value on a global scale. Globally, L. vannamei contributes around 2.8 million tonnes

followed by P. monodon (0.8 million ton). Shrimp aquaculture in India also has shown a

tremendous growth (30.64%) with a record production level of 4,34,558 ton. Of the total

shrimp produced in 2014-15, production of L. vannamei increased by 41% to 3,53,413 ton

where as black tiger shrimp (P. monodon) production remained stagnant at 71,400 ton.

However, the recent data indicate that export of black tiger shrimp has picked up from

negative growth during 2013-14 to a positive growth of 0.64% during 2014-15.

5.3. Culture/ farming system

The country has vast potential for brackishwater aquaculture development in the coastal

saline affected lands with a total estuarine area of 3.9 million ha and backwaters of 3.5

million ha. Among these coastal salt affected lands, 1.2 million ha has been identified to

be potentially suitable for shrimp farming. Out of these total areas available, hardly 16%

has been developed into shrimp farming which includes 4% of traditional farming in West

Bengal, Kerela, Goa and Karnataka.

5.3.1. Traditional farming

Brackishwater aquaculture traditionally practiced in West Bengal is called the bheri or

bhasabhandha fishery where tidal water is impounded in inter-tidal mudflats by raising

bunds. At present, about 44,000 ha is under this system producing 500–750 kg/ha and

shrimps contribute 20–25% of the total production. In Kerela, shrimp culture is practiced

by trapping tide water after harvesting rice in the seasonal fields known as “Pokkali”. In

Karnataka, shrimp culture is traditionally carried out in kharlands after a crop of „Kagga‟,

a salt resistant variety of paddy. About 2,500–3,000 ha is under this type of culture. In

Goa, around 500 ha of „khazan‟ lands are under traditional farming.

5.3.2. Scientific shrimp farming

Scientific methods of shrimp farming include proper husbandry protocols such as removal

of pests and predators, development of natural food by using manures and fertilizers,

stocking of healthy seed, feeding with nutritionally balanced feed, monitoring and

maintenance of water quality and health management. In these methods, various degrees

of control are maintained and accordingly various types have been classified.


63

5.3.2.1. Improved traditional

In this farming method, the improvement over the traditional approach is in the

introduction of selective stocking and supplementation with locally made feed to increase

the production and productivity. This culture method takes advantage of water being

constantly renewed through tidal fluctuations and by water current. Stocking density

generally followed is between 40,000 and 60,000 nos./ha.

5.3.2.2. Extensive/ modified extensive/ improved extensive

There is not much difference between improved traditional and extensive systems.

Stocking density also remains at the same level. Supplementary feed either formulated or

fresh, is given daily in addition to the existing natural food produced through the

application of fertilizers. This operation also requires the use of a water pump to facilitate

water exchange. The system is either tide-fed or pump-fed.

5.3.2.3. Semi Intensive

In this type, stocking density is very high which goes up to 1–3 lakhs/ha. Water quality

management increased with the addition of pond aeration. Animals are fed with high

protein diets with strict feed management. Animal‟s health is also monitored at regular

intervals. In India, such high stocking density is not permitted by the CAA.

5.3.2.4. Super- intensive

The distinct features of this culture operation are the complete dependence on hatchery-

bred seed, high stocking density, use of formulated feeds, application of aeration to

increase dissolved oxygen level in pond water and intensive water management. The

shrimps are cultured under fully controlled conditions with high stocking density of 100–

200 nos./m2. Presently, super intensive system is not being practiced in the country.

5.4. Advances in culture system of L. vannamei

5.4.1. Open system

In open system, exchange of more than 20% of the total pond volume at one time is

necessary in order to reduce pond wastes and the density of the plankton. Seeds can be

stocked up to 60 PL/m2 and will grow to 25–35 g within 120 days. The open system has

recently become less favourable to farmers since the environmental conditions, especially

the quality of water, tend to deteriorate with time.


64

5.4.2. Closed System

This system involves filling up the pond with cleaned seawater which are disinfected using

chemicals. The shrimps are stocked up to 30 PL/m2 and cultured for a period of 100–120

days to attain the average weight of 15–20 g. Water loss due to evaporation and seepage is

replenished with seawater or freshwater by pumping. The disadvantages of this system are

that it requires low stocking density and high efficient water and waste management.

However, it can be operated anywhere, even in the inland area where seawater is not easily

accessible.

5.4.3. Re-circulatory system

Integrated closed recirculation system in intensive shrimp culture is one strategy that

minimizes waste from culture systems and the risk of disease. RAS typically includes

shrimp rearing tanks/ ponds sustained by a water treatment process, which is focused on

the detoxification of nitrogenous wastes, oxygenation, removal of suspended solids, and

typically water exchange not exceeding 10%. To operate the system, cleaned seawater is

initially pumped into the pond and kept within the system. During the culture period, the

effluent from culture pond is drained into the sedimentation pond, treated with chemicals

and pumped into the reservoir for supply to culture ponds. The stocking density for this

system generally varies between 30–50 nos./m2

and the culture period is up to 130 days.

5.4.4. Zero-discharge raceway system

In this system, a greenhouse enclosed, plastic lined raceways outfitted with foam

fractionator (FF), and settling tank are stocked with juvenile Pacific whiteleg shrimp at

high density and operated with no water exchange. They are also equipped with spray

nozzles and airlift pumps for constant movement and aeration of the water. This system is

practically done on experimental scale in European countries and has not been taken up in

India.

5.4.5. Biofloc based culture system

Biofloc, a super intensive aquaculture technology seems a very promising for stable and

sustainable production as the system has self-nitrification process within culture ponds

with zero water exchange. A C:N ratio above 10:1 is optimal for generation of biofloc

which can be maintained by adding locally available carbon sources. Fish and shrimp use

these microorganisms aggregated as additional feed source to increase productivity, reduce

FCR, possibly prevent diseases for a consequently sustainable production. Production per


65

unit area is high in biofloc system. The stocking density of animals in HDP-lined biofloc

pond is twice the density of an ordinary shrimp pond ranging from 250 to 500 PL/m2.

Production per hectare in a conventional pond is 10-15 ton, while a biofloc pond gives out

20–30 ton.

5.5. Biosecurity measures in shrimp farming

The biosecurity measures include farm to be fenced (including crab fencing), installation

of bird fencing, water intake through reservoirs, separate implements for each pond,

effluent treatment system (ETS) in position, usage of only feed manufactured by reputed

companies and proper maintenance of records regarding seed procurement source,

quantity, stocking density etc. as well as quantity of shrimp produced and sold indicating

the name and address of processors.

5.5.1. Good pond management practices in shrimp culture

5.5.1.1. Pond bottom soil removal

The upper 25 to 75 cm layer of soil should be removed after complete draining and drying

of pond. This top layer contains high organic content resulting from deposition of uneaten

feed and faecal matter during the culture period. High concentration of organic matter can

lead to anaerobic sediment that can have adverse effect on shrimp growth and survival.

5.5.1.2. Water intake

Intake water must be filtered at the main sluice and at each pond feeder pipe with fine

mesh screen filter bag (60 mesh/inch) to prevent entry of vectors and pathogens that

maybe present in the source water. The water must be disinfected with 60 ppm of calcium

hypochlorite and left for a week.

5.5.1.3. Seed Stocking

Only quality seed should be procured for culture and PCR testing should be done to ensure

virus free seed. L. vannamei seed should be procured only from hatcheries authorized for

import of broodstock and/or production of seed. Before stocking at pond, PL should be

treated with formalin at 100 ppm concentration for 30 min in well aerated tanks and

acclimatized gradually to pond salinity, temperature and pH. Stocking density should not

exceed 60 nos./m2 for L. vannamei and 10–12 nos./m

2 for P. monodon.


66

5.5.1.4. Soil and water quality management

In any shrimp farming, management of water quality is of primary consideration

particularly in ponds with higher stocking rates. Degradation of water quality is

detrimental to shrimp growth and survival. Good quality water is usually defined as the

fitness or suitability of the water for survival and growth of shrimp. Regular monitoring of

soil and water quality parameters like temperature, salinity, pH, dissolved oxygen, TAN,

nitrate, nitrite, total suspended solids, etc. should be done.

5.5.1.5. Pond aeration

Aeration of ponds should be carried out to increase the dissolve oxygen and remove

stratification in ponds. L. vannamei in particular is sensitive to oxygen stress and since a

higher stocking density is maintained all along, aeration is very critical aspects in L.

vannamei farm.

5.5.1.6. Feeding management

One of the most important operational functions in shrimp culture is the provision of

adequate food supply to ensure that the cultured animals attain the desired harvesting size

within the targeted time frame. Optimal feeding rate and frequency are essential in

maximizing conversion rate of feed to shrimp biomass. Check tray should be monitor at

interval to avoid overfeeding or underfeeding of shrimp, and feed requirements must be

calculated as per the standing biomass. Feeding is usually done @ 5% of total biomass at

the beginning which is gradually reduced to 3.5% at the end of culture period.

5.5.1.7. Health management

Shrimp should be sampled once a week and should be checked for their general health

condition like external appearance (body colour, missing appendages, external/ gill

fouling, black gills or gill choking, etc.), gut condition, and growth in terms of weight or

length. Shrimp behavior and feeding trends should also be monitored. The gut content

colour is a good indicator of the probable health status and corrective action to be taken. A

black/ brown/ green gut implies under feeding whereas a red or pink gut indicate disease

manifestation, whereas a pale whitish gut showed gut infection. A normal gut will have a

light or golden brown colour.


67

5.5.1.8. Effluent treatment system (ETS)

Pond effluents should be treated and should conform to the standards prescribed under the

Guidelines issued by the CAA. Waste water should be retained in the ETS for a minimum

period of two days. Treatments may include disinfector or biological filtration through

cultivation of algae, seaweeds, clams and filter feeders or omnivorous fishes to reduce the

excess organic matter and pathogen. In case of disease outbreak, water should be

chlorinated and dechlorinated before discharge into the drainage system.

5.5.1.9. Farm record maintenance

Maintenance of record is necessary to identify problems in the pond environment and

shrimp health, and to rectify these problems at the earliest during the production cycle.

Record keeping also helps the farmer to learn from past mistakes, thus reducing risk and

costs of production in subsequent crops. Records are useful to plan the entire crop cycle

including stocking densities for each pond, well ahead of its start. Farm records ideally

should contain details on pond preparation, seed and its stocking, feed management, water

quality parameters and its management, pond bottom management, shrimp health and

harvest. The farm data maintenance sheet should be used for the purpose.

5.6. Role of Coastal Aquaculture Authority in L. vannamei farming in India

In India, farming of L. vannamei is allowed only in the hatcheries and farms that are

registered with CAA and strict bio-security as spelt out in the guidelines shall have to be

maintained. The CAA shortlisted SPF L. vannamei broodstock suppliers based on the

genetic base and disease status, and import of SPF broodstock shall be permitted only

from such suppliers. After obtaining the letter of permission from CAA for import of

broodstock and seed production, the hatchery operators have to apply to the DAFH & F,

Govt. of India for Sanitary Import Permit (SIP) which is valid for six months and can be

extended by the competent authority for a further period of six months on request from

importers. The quarantine of the imported broodstock would be ensured through the

Aquatic Quarantine Facility (AQF) set up at RGCA, Neelankarai at Chennai. Hatchery

operators permitted by CAA should sell post larvae of L. vannamei only to farm registered

with CAA.


68

Further readings

State of Fisheries and Aquaculture (2014). Food and Agricultural Organization. Rome.

www.caa.gov.in

Handbook of Fisheries and Aquaculture. (2011). Indian Council of Agricultural

Research. New Delhi.

Shrimp Health Management Extension Manual. (2003). MPEDA/NACA. India.

http://www.fao.org/fishery/culturedspecies/Penaeus_vannamei/en#tcNA0112.


69

Soil and Water Quality Management in

Brackishwater Aquaculture

R. Saraswathy, P. Kumararaja and M. Muralidhar

ICAR-Central Institute of Brackishwater Aquaculture, Chennai

6.1. Introduction

Successful aquaculture largely depends on providing animals with a satisfactory

environment to grow. The most important principle regarding soil and water is that a pond

has a finite capacity to assimilate nutrients and organic matter. When the capacity is

exceeded, water and soil quality will deteriorate resulting in growth inhibition,

vulnerability to diseases and ultimately mortality. Soil and water quality can be maintained

within the optimal range by giving due importance right from site selection, suitable pond

preparation, good culture practices and post-harvest pond management for next crop.

Maintaining a good pond environment through use of proper management practices will

reduce the stress, risk of disease, increase production and improve productivity and

livelihood.

6.2. Soils

Soils provide the base on which aquaculture ponds are built and obviously play a major

role. The condition of pond bottom influences water quality and production.

Concentrations of nutrients and phytoplankton productivity in pond water are related to

pH and nutrient concentration in soils. Before initiating aquaculture operation, one should

be well acquainted with the nature of soil as it affects the production.

6.2.1. Soil texture

Soil texture refers to the relative percentage of sand, silt and clay in the soil and has a

direct effect on the productivity of ponds. Clayey soils with 18–35% clay are best suited

for constructing bunds and have good water retention properties. Sandy soil is porous and

is very poor material for constructing bunds. Therefore, brackishwater soils with

moderately heavy texture such as sandy clay, sandy clay loam and clay loam are highly

suitable for aquaculture.

6


70

6.2.2. pH

pH indicates the acidic or alkaline nature of the soil. It is an important parameter as it

influences availability of nutrients, rate of mineralization, bacterial activities and fixation

of phosphorus. In general, soil pH ranging between 6.5 and 7.5 are best suited for

brackishwater aquaculture. Within this pH range, the availability of nitrogen, phosphorus,

potassium, sulfur, calcium and magnesium concentration is maximum.

6.2.3. Calcium carbonate

Soil rich in CaCO3 content promotes biological productivity as it enhances the breakdown

of organic substances by bacteria creating more favourable oxygen and carbon reserves. It

decreases BOD and enhances nitrification due to the requirement of calcium by nitrifying

organisms. The productive soil should have calcium carbonate more than 5%.

6.2.4. Organic matter

Organic matter is an important index of soil fertility. It helps in prevention of seepage loss,

increases arability of pond bottom and supplies nutrients. It reduces turbidity of pond

water and act as antioxidants. Organic matter influences microbial activity and

productivity of pond. Soil which has organic carbon content less than 0.5% is low

productive, 0.5–2% is medium productive and > 2% is highly productive. Optimum value

is 1.5–2%.

6.3. Soil quality management

Even if the site is good with optimum soil characteristics, problems may still crop up due

to the large quantity of inputs like feed and fertilizers which lead to excessive

phytoplankton production, low DO, high ammonia, poor bottom soil condition and other

problems. Most of these problems can be avoided by proper management practices during

pond preparation and culture period.

6.3.1. Pond preparation

The main objectives of pond preparation are to provide the animal with a clean pond base

and appropriate stable water quality. Pond preparation is generally dealt in two categories

viz., newly constructed ponds and existing culture ponds. In newly dug out ponds, the

characteristics of the soil has to be understood and appropriate measures to be followed

instead of waiting until poor bottom soil quality develops later. It is highly recommended

to analyse the soil quality and its characteristics by professionals before starting the


71

culture. Pond preparation after harvest is completely different from newly excavated

ponds. Following are the importance practices to be followed.

6.3.1.1. Pond mud drying and sediment removal

When ponds are drained for harvest, nutrients and planktons are discharged, and the

flocculent layer of highly organic material and many of the benthic organisms which

thrive in the soil-water interface are suspended and lost from ponds. Pond bottom should

be left to dry for at least 7–10 days or till the soil cracks to a depth of 25–50 mm for

proper mineralization of organic matter and release of nutrients. Drying of ponds

maintains hygienic conditions and stimulates oxidation of materials that result in release of

noxious gases such as hydrogen sulphide, ammonia and methane. The sludge left in the

pond after drying, may contain high organic load, bacteria, viral particles and many other

viral carriers. All these should be removed to prevent the persistence of viral diseases.

This can be achieved by the application of burnt lime @ 100 ppm followed by exposure of

the pond bottom to sunlight, removal of top soil and compacting the bottom soil. Drying

and cracking of pond bottom enhance aeration and microbial decomposition of organic

matter. In situations where complete drying is not possible, organic and biodegradable

piscicides such as Mahua oil cake (100–150 ppm) and tea seed cake (15–20 ppm) can be

used. A minimum period of 10 days should be provided to degrade the viral/ bacterial

effects completely. Calcium carbide can be used to destroy the carb. Ammonium sulphate

(one part) in combination with lime (five parts) can be an effective eradicating material.

Tilling of pond bottom during dry period enhances aeration, improves organic matter

decomposition and oxidation of reduced compounds. Heavy textured soils (clays and clay

loam) will benefit more from tilling than light texture soil (sands, sandy loam and loam).

Tilling should be done with a disc harrow and limited to a depth of 5 to 10 cm. Sediment

disposal should be done in a way to prevent the sediment from washing into ponds or

canals after heavy rains and to avoid adverse ecological impacts outside of ponds. Site

specific methods of sediment disposal must be developed for each farm.

6.3.1.2. Liming

Liming helps to neutralize the soil acidity, enhances availability of nutrients, accelerates

microbial activity and maintains alkalinity. It also improves the hygiene of the pond

bottom and increases production. To estimate liming dose, either pH or total alkalinity

may be used. Brackishwater ponds with total alkalinity below 60 ppm or pH below 7


72

usually will benefit from liming. The amount of different lime materials required to raise

the pH to 7 is given in the following table. Agricultural lime stone will not react with dry

soil, so it should be applied while soils are still visibly moist but dry enough to walk on.

Table: Amount of lime (ton/ha) to raise the soil pH to 7

Soil pH Quantity of lime material (ton/ha)

Dolomite Agricultural lime Quick lime

6 to 6.5 5.7 to 2.8 5.5 to 2.8 4.6 to 2.3

5.5 to 6.0 8.5 to 5.7 8.3 to 5.5 6.9 to 4.6

5.0 to 5.5 11.3 to 8.5 11.1 to 8.3 9.2 to 6.9

4.5 to 5.0 14.2 to 11.3 13.9 to 11.1 11.5 to 9.2

4.0 to 4.5 17.0 to 14.2 16.6 to 13.9 13.8 to 11.5

6.3.1.3. Fertilization

Decomposition in organic soil is slow because pH usually is low and the amount of carbon

relative to nitrogen is high. Urea (200 to 400 kg/ ha) or sodium nitrate (20 to 40 kg/ ha)

can be applied to accelerate the decomposition of organic soil. Depending upon the

phytoplankton density as exemplified by turbidity of the pumped water, required quantity

of the fertilizers may be applied in split doses at short intervals for sustained plankton

production.

6.3.2. Management of pond bottom during culture

Various physical, chemical and biological processes occur in the aquaculture pond bottom,

often referred to as the sediment. The oxidized layer at the sediment surface is highly

beneficial and should be maintained throughout the culture period. Ponds should be

managed to prevent large accumulations of fresh organic matter at the soil surface or in the

upper few millimetres of the soil and are called as sediment-water interface. It is an

intricate system where complex chemical and microbial changes occur and plays an

important role in brackishwater aquaculture. To understand the condition of pond bottom,

the following parameters are to be monitored regularly.


73

6.3.2.1. pH of soil

This is one of the most important soil quality parameters since it affects the pond

condition. Generally, soil pH ranging between 6.5 and 7.5 is best suited for aquaculture,

where availability of nitrogen, phosphorus, potassium, calcium and magnesium is

maximum. Lower pH of bottom sediment indicates unhygienic condition and needs

regular checkup.

6.3.2.2. Redox-potential

In sediments, when organic matter exceeds the supply of oxygen, anaerobic condition

develops. This reducing condition can be measured as the redox potential and is

represented as Eh. Negative redox value shows reducing condition whereas positive value

shows aerobic condition. Reaction under aerobic and anaerobic condition is given in the

figure below. Under anaerobic condition, some microorganisms decompose organic matter

by fermentation reactions that produce alcohols, ketones, aldehydes and other organic

compounds as metabolites. Other anaerobic microorganisms are able to use oxygen from

nitrate, nitrite, iron, manganese oxides, sulphate and carbon di-oxide to decompose

organic matter and release nitrogen gas, ammonia, ferrous, manganous, manganese,

hydrogen sulphide, methane and metabolites. The redox potential of sediment should not

exceed –200 mV. Water circulation by water exchange, wind or aeration helps to move

water across mud surface and prevent the development of reduced condition. Bottom

should be smoothened and sloped to facilitate draining of organic waste and toxic

substances. Central drainage canal in the pond may also help in the removal of organic

waste periodically.


74

6.3.2.3. Organic matter

Unutilized feed, carbonaceous matter, dissolved solids, faecal matter, dead plankton etc.

settle at the pond bottom resulting in the accumulation of organic loads. The change in the

bottom in terms of increasing organic load should be recorded regularly for better pond

management.

6.4. Water quality management

Maintenance of good water quality is essential for both survival and optimum growth of

animal. Water treatment is necessary during pond preparation for maintenance of good

water quality at later stages. Water from the source should be filtered through 60 µ filters

to prevent the entry of parasites and crustaceans that are carriers of diseases. Inorganic

turbidity should be removed by providing sedimentation/ reservoir pond before water is

taken into production ponds. Chlorination should be done in reservoir pond to sterilize the

water by applying enough chlorine (approximately 30 ppm) to overcome the chlorine

demand of organic matter and other substances in the water. Chlorine dose varies with pH,

concentrations of organic matter and ammonia. Water has to be pumped in the grow-out

pond after 12 days of treatment, at which time, the permissible levels of chlorine residuals

Pond Water

Sediment Aerobic layer

Anaero

bic

layer

Sedim

ent depth

Oxygen reduction

1/2O2 + 2e- + 2H

+ --> H2O

Nitrate and Manganese reduction

2NO3- + 12H

+ + 10e

- --> N2 + 6H2O (Denitrifiers)

MnO2 + 4H+ + 2e

- --> Mn

2+ + 2H2O (Manganese reducing bacteria)

Iron reduction

Fe(OH)3 + 3H+ + 2e

- --> Fe

2+ + 2H2O (Iron reducing bacteria)

Sulphate reduction

SO42-

+ 10H+ + 8e

- --> H2S + 4H2O (Sulphate reducing bacteria)

Methane formation

CO2 + 8H+ + 8e

- --> CH4 + 2H2O (Methanogens)


75

should be less than 0.001 ppm. Intense aeration, addition of 1 mg/L of sodium thio-sulfate for

every mg/L of chlorine and exposure to sunlight are some of the management practices.

During culture, the parameters that should be monitored routinely are water temperature,

salinity, pH, dissolved oxygen, total alkalinity, minerals, nutrients and metabolites.

6.4.1. Physical characteristics

6.4.1.1. Water temperature

Temperature of water is obviously very vital. All metabolic and physiological activities

and life processes such as feeding, reproduction, movement and distribution of aquatic

organisms are greatly influenced by water temperature. Temperature also affects the speed

of chemical changes in soil and water, and the contents of dissolved gases. On account of

unequal distribution of temperature with higher temperature near the surface layer and

decreasing temperature with depth, thermal stratification can occur resulting in formation

of methane, hydrogen sulphide and ammonia causing degradation of water quality.

Optimum level of pond water temperature is 25–30°C. Operation of aerators during warm

and calm afternoons helps to break thermal stratification by mixing warm surface water

with cool sub-surface water.

6.4.1.2. Salinity

Salinity refers to the total concentration of ions in water (calcium, magnesium, sodium,

potassium, bicarbonate, chloride and sulphate). It determines osmotic relationships and

also affects the growth, reproduction and migratory behaviour of the animal as well as its

general metabolism. In brackishwater ponds, the salinity of water varies with the salinity

of the estuarine water supply. During the wet season, high discharges of freshwater from

rivers into estuaries cause salinity values to decline, whereas low or no discharges of

freshwater during the dry season result in higher salinities. Maintenance of salinity of 18

to 35 ppt with variations not exceeding 5 ppt will help in reducing stress on the animal.

The stress response associated with the sudden decrease in salinity is reduced when the

calcium concentration of the low salinity is increased from 84 to 150 ppm.

6.4.1.3. pH

The initial pH of pond waters (before biological activity adds to or removes CO2 to water)

is a function of the total alkalinity of the water. pH of most pond water is determined by

interactions among dissolved CO2, carbonic acid, bicarbonate, carbonate and carbonate


76

containing minerals. pH can fluctuate between 7.5 and 9.5 with the accumulation of

residual feed, dead algae and excreta over a 24 h period with lowest pH occurring near

dawn and the highest pH occurring in the afternoon. Unusually high afternoon pH values

typically occur in waters of moderate to high total alkalinity (50–200 ppm as CaCO3) and

low total hardness (< 25 ppm as CaCO3). The proportion of total ammonia existing in the

toxic, un-ionized form (NH3) increases as the pH increases whereas low pH increases nitrite

toxicity and also the fraction of H2S (toxic form). However, the pH of brackishwater is usually

not a direct threat to the health of the aquatic animal, since it is well buffered against pH

changes. Calcium is a particularly important modulator of pH toxicity because calcium affects

the permeability and stability of biological membranes. Optimum level of pH is between 7.5

and 8.5.

6.4.1.4. Turbidity

Turbidity refers to an optical property of water that causes light to be scattered or absorbed

rather than transmitted through the water in a straight line. Turbidity can be measured in

terms of transparency using secchi disc. Turbidity caused by plankton is desirable whereas

turbidity resulting from suspended particles of clay is undesirable in aquaculture ponds. It

will restrict light penetration, adversely affecting plant growth and destroy benthic

organisms. In case of very high turbidity, fish die due to gill clogging. High value of

transparency (> 60 cm) is indicative of poor plankton density and the water should be

fertilized with right kind of fertilizers. Low value (< 20cm) indicates high density of

plankton and hence fertilization rate and frequency should be reduced. Optimum range of

transparency is 25–35 cm. Alum (aluminium sulfate) is an excellent coagulant and is used

widely in water-treatment plants to clarify the water. Calcium sulfate, calcium hydroxide

calcium ferric chloride, organic matter, certain synthetic polymers and chemical fertilizers

are used in removing suspended solids from ponds.

6.4.2. Chemical characteristics

6.4.2.1. Dissolved oxygen

Dissolved oxygen is the most important and critical water quality parameter because of its

direct effect on the feed consumption and metabolism of animal as well as indirect

influence on the water quality. The concentration of toxic substances such as unionized

NH3, hydrogen sulphide and carbon metabolites (methane) increases when low DO level

exists. However, in the presence of optimum level of oxygen, the toxic substances are


77

converted into their oxidized and less harmful forms. Optimum DO concentration for

aquatic animal growth is 3–10 ppm. Aeration is the best option to maintain DO

concentration. Use of aerators result in mixing of water at surface and bottom and breaks

down DO stratification and can also eliminate black mud formed at soil-water interface.

Paddle wheel aerators are commonly used and the latest ones such as the long arm aerators

and spiral aerators can circulate oxygen to the pond bottom more effectively. Management

of DO in pond waters is very closely related to the amount and type of phytoplankton,

animal biomass, organic matter in the pond and bacterial activity. Generally one

horsepower of aerator is suggested for every 500 kg production. Water exchange is the

best solution to prevent low DO problem in the pond where aeration is not practiced, but it

comes with the inherent risk of disease outbreak.

6.4.2.2. Minerals

Minerals are important for the growth and metabolism of animals. Among the minerals,

the ratio of Na to K and Ca to Mg in the water are highly important for survival, growth

and production rather than salinity. The ratio of minerals should be maintained similar to

the ratio of sea water. In general, water is suitable for aquaculture if levels of minerals are

similar to the levels in seawater diluted to same salinity. In order to calculate the desired

mineral levels at different water salinities, the water salinity (in ppt) is to be multiplied by

the factors shown for each mineral.

Minerals

Salinity

1 ppt 5 ppt 10 ppt

Calcium (ppm) 11.6 58.0 116.0

Magnesium (ppm) 39.1 195.5 391.0

Potassium (ppm) 10.7 53.5 107.0

Sodium (ppm) 304.5 1522.5 3045.0

Generally the deficiency of mineral is seldom observed in high saline water,

whereas after introduction of L. vannamei, farmers are very keen on mineral application. If

pond water is deficient with the above said mineral, it has to be corrected by the addition

of following salts.


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Minerals Chemical formula General name %

Calcium sulphate Ca2SO42H2O

Gypsum Ca: 22%

SO4: 55%

Potassium chloride KCl Murate of potash K: 50%

Cl: 45%

Potassium

magnesium sulphate

K2SO42MgSO4

K-Mag K: 17.8%

Mg: 10.5%

SO4: 63.6%

Potassium sulphate K2SO4 - K: 41.5%

SO4: 50.9%

Hydrated

magnesium sulphate

MgSO47H2O

Epsom Mg: 10%

SO4: 39%

Amount of salt to be added in the pond will be calculated based on the desired mineral

level and the selected salt.

• Amount of salt to be added = Concentration of minerals required in the pond (in

ppm) / % of mineral ions in the selected salt.

• For example, to get the potassium content of 200 ppm, the amount of murate of

potash to be applied = 200 / (50% / 100) = 400 mg / L

6.4.2.3. Total alkalinity

Total alkalinity is the sum of titrable bases in water, predominantly bicarbonate and

carbonate. Alkalinity of pond water is determined by the quality of the water supply and

nature of pond bottom soils. It is the capacity of water to buffer against wide swings in pH

and enhanced natural fertility of water. Ponds with a total alkalinity of 20–150 ppm have

sufficient supply of CO2 for phytoplankton growth and it may improve productivity. It

also decreases potential of metal toxicity. Very high alkalinity (200–250 ppm) coupled

with low hardness (less than 20 ppm) results in rise in afternoon pH beyond 11 and causes

death of animal. Dolomite, shell lime and zeolite improve alkalinity and stabilize pond

water quality.


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6.4.3. Metabolites

6.4.3.1. Ammonia

Ammonia in the pond water is a by-product of metabolism by animals and decomposition

of organic matter by bacteria. As ammonia in water increases, ammonia excretion by

aquatic organism diminishes, and levels of ammonia in blood and other tissue increases. In

water, ammonia-nitrogen occurs in two forms, un-ionized ammonia and ammonium ion

(NH4). Un-ionized ammonia is determined by total ammonia concentration, pH, and water

temperature and to a lesser extent on salinity. It is considered more toxic form of ammonia

due to its ability to diffuse readily across cell membrane, hence should be less than 0.1

ppm. A given concentration of un-ionized ammonia is more toxic when dissolved oxygen

concentrations are low. Ammonia toxicity reduces when salinities are near the optimum

levels and when high concentrations of calcium are present. Toxic effect of ammonia may

be minimized by maintaining sufficient level of dissolved oxygen, periodic partial removal

of algal blooms and water exchange.

6.4.3.2. Nitrite

Nitrite is an intermediate product in the bacterial nitrification of ammonia to nitrate.

Nitrite is highly toxic to fish as it oxidizes haemoglobin to form methaemoglobin, which is

incapable of transporting oxygen. Nitrite toxicity is affected by water pH and the presence

of chloride and calcium ions. Toxicity increases with increasing pH and decreases with

increasing calcium and chloride concentrations. Optimum level of nitrite is less than 0.25

mg/L. Optimum level can be maintained by effective removal of organic waste, adequate

aeration and correct application of fertilizer.

6.4.3.3. Hydrogen sulfide

Under anaerobic condition, certain heterotrophic bacteria can use sulphate and other

oxidized sulphur compounds as terminal electron acceptors in metabolism and excrete

sulphide. pH regulates the distribution of total sulphide among its forms (H2S, HS- & S

2-).

Un-ionized H2S is toxic and it decreases rapidly with increasing pH. H2S builds up mostly

in sediment which is highly reduced (redox potential < 100 mv), within a pH range of 6.5–

8.5 and low in iron. Sulfide can be reduced by aeration, water exchange and circulation of

water to minimize anaerobic zones in the pond bottom. Application of lime or potassium

permanganate or iron oxide will reduce hydrogen sulfide. Iron reacts with H2S and forms

insoluble iron sulphide. Periodic pond draining and drying of bottom muds will result in


80

oxidation of sulfide and enhance the decomposition of organic matter. Concentration of

H2S more than 0.01 mg/L may be lethal to aquatic organisms.

The optimum soil and water quality parameters for brackishwater aquaculture have been

summarized in the table below.

Soil Water

Parameters Optimum range Parameters Optimum range

pH 6.5–7.5 Temperature (oC) 28–32

Electrical conductivity

(dS m-1

)

> 4 pH 7.5–8.5

Clay content (%) 18–35 Salinity (ppt) 15–25

Texture Sandy clay, sandy

clay loam, clay loam

Transparency (cm) 30–40

Organic carbon (%) 1.5–2.0 Total suspended solids

(ppm)

< 100

Calcium carbonate

(%)

> 5 Dissolved oxygen

(ppm)

4–7

Available N

(mg/100g)

50–70 Chemical oxygen

demand (ppm)

< 70

Available P (mg/100g) 4–6 Biochemical oxygen

demand (ppm)

< 10

Total ammonia N

(ppm)

< 1

Free ammonia N

(ppm)

< 0.1

Nitrite N (ppm) < 0.25

Nitrate N (ppm) 0.2–0.5

Phosphate (ppm) 0.1–0.2


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6.5. Conclusion

Of the many factors that affect the production and productivity of aquaculture, soil and

water quality play a pivotal role. Deterioration of pond environment leads to stress to

animals and increases susceptibility to diseases. Key to successful aquaculture is

intervention at the right time through appropriate management practices. Hence, it is

imperative to constantly monitor and maintain soil and water quality parameters within the

optimum range. pH and redox potential are the important soil parameters and they should

be monitored at least once a week. Similarly, the key water quality parameter, dissolved

oxygen, should be measured at dawn and late afternoon, which will normally provide

information on the daily extremes. pH and metabolites should be measured at weekly

intervals as a minimum. Apart from the monitoring of the pond conditions, observing

animal behaviour along with accurate record keeping helps the farmer to recognize and

prevent deleterious environmental conditions through better management practices at early

stages and thereby maximize the production.


82

Nutrition, Feed Formulation and

Feed Management in Brackishwater Aquaculture

T.K. Ghoshal and Debasis De


7.1. Introduction

In modern aquaculture, formulated feed is one of the most vital inputs and feed cost alone

contributes to 50–60% operational cost. Hence, knowledge on nutritional requirement of

each candidate species, proper feed formulation and its proper management in aquafarm

are very much essential for success of aquaculture. Preparation of nutritionally adequate

feed for fish and shrimp involves understanding the dietary requirements of the species,

proper selection of feed ingredients, formulation of feeds and appropriate processing

technology for producing water stable pellet feeds.

The performance and success of a formulated aquafeed depends on many factors,

the most important being:

Feed formulation and nutrient content of feed ingredients.

Feed manufacturing process and physical characters of the feed.

Feed handling and storage.

On-farm feed management: feed application methods, feeding regime.

Aquatic environment and natural food availability.

7.2. Nutritional requirement

7.2.1. Protein and amino acid requirements

Like other animals fish and crustaceans require food to supply the energy that they need

for movement and all other activities that they engage in and the „building blocks‟ for

growth. However, they are „cold-blooded‟ and as their body temperature is the same as the

water they live in, they do not therefore have to consume energy to maintain a steady body

temperature and they tend to be more efficient users of food than other farm animals. Food

requirement of different species of finfish and shellfishes vary in quantity and quality

according to the nature of the animal, its feeding habits, size, environment and

7


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reproductive state. Fish and crustaceans require food protein in the form of essential amino

acids for maintenance of life, growth and reproduction and the requirement of protein

depends on animal characteristics, i.e., species, physiological stage, size as well as dietary

characteristics, i.e. protein quality (digestibility and biological value), energy level etc. and

also abiotic factors, i.e. temperature, salinity etc. The protein requirement of aquatic

animals is higher than terrestrial animals which might be a consequence of the low energy

requirements of ectothermic animals. Moreover, the scarcity of carbohydrates and

abundance of protein and lipids in the natural aquatic food web is also probably

responsible for the common trend of aquatic organisms to use protein as an energy source.

Protein is the most important and essential nutrient in diet of shrimp and fish. Protein

requirement in terms of dietary concentration (% of diet) is high. Protein is required in the

diet to provide indispensable amino acids and nitrogen for synthesis of non-indispensable

amino acids. A deficiency of indispensable amino acid creates poor utilization of dietary

protein and hence growth retardation, poor live weight gain and feed efficiency. In severe

cases, deficiency reduces the ability to resist diseases and lowers the effectiveness of

immune response mechanism. For example, experiments have shown that tryptophan

deficient fish becomes scoliotic, showing curvature of spine, and methionine deficiency

produces lens cataracts.

Protein (amino acids) is used as a major energy source. Some economy can be

made here if other dietary fuels are present in adequate amounts, e.g. increasing the lipid

(fat) content of diet can help reduce dietary protein (amino acid) catabolism and

requirement. This is referred to as protein-sparing effects of lipids. Protein requirement

varies with age of the fish and crustaceans. Younger animals generally require higher level

of protein (5–10% more protein) than older animals. Carnivores require high dietary

protein (40–50%) than omnivores (25–35%). The protein requirement varies with size of

shrimps and also with the source of protein used in diet. The dietary requirement of

protein for tiger shrimp, Penaeus monodon ranges from 35 to 45% and for

Fenneropenaeus indicus it ranges from 30–43%, which are the most important species for

culture. It has been demonstrated that postlarvae and juveniles require higher protein in

diet and the requirement decreases as the shrimp grows larger in size. Among

brackishwater finfishes, requirement of protein for Asian seabass (Lates calcarifer),

milkfish (Chanos chanos) and grey mullet (Mugil cephalus) is 40–45%, 40% and 35–40%,

respectively.


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7.2.1.1. Amino acids

Growth of fish and shrimp is directly related to the quality of protein in terms of amino

acids. After digestion of protein, amino acids are metabolized at tissue level to form new

proteins for growth, maintenance and energy. Protein in body tissues incorporates about

23 amino acids and among these, 10 amino acids must be supplied in the diet since fish

and shrimps cannot synthesize them. These are termed as essential amino acids (EAA) and

include arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine,

threonine, tryptophan and valine. Amino acids are needed for maintenance, growth,

reproduction and repletion of tissues. A large proportion of the amino acid consumed by a

fish is catabolized for energy and fish are well adapted to using an excess energy in this

way. It is found that if the amino acid composition of protein in the feed matches with the

amino acid composition of shrimp body tissue, such feed promotes good growth.

Catabolism of protein leads to the release of ammonia.

7.2.2. Lipid requirement

Lipids (fats) encompass a large variety of compounds and a complex mixture of simple

fat, phospholipids, steroids, fatty acids and other fat soluble substances such as pigments,

vitamins A, D, E and K. Lipids have many roles: energy supply, structure, precursors to

many reactive substances etc. Phospholipids are responsible for the structure of cell

membranes (lipid bi-layer). Fatty acids are the main active components of dietary lipids.

Deficiency of essential fatty acids result, in general, in reduction of growth and a number

of deficiency signs including depigmentation, fin erosion, cardiac myopathy, fatty

infiltration of liver and „shock syndrome‟ (loss of consciousness for a few seconds

following an acute stress). The quantitative requirement of fat in the diet of shrimp is in

the range of 5 to 10%. Fat levels of 6–8% are adequate in most of the fish diets. However,

the quality of fat in terms of fatty acids is more important.

7.2.2.1. Fatty acids

Fish and shrimps are unable to synthesize fatty acids of the n-3 and n-6 series and they

must be provided in their diets. Aquatic animals require higher n-3 fatty acids than

terrestrial animals. Among aquatic animals, marine habitat requires more HUFA than

freshwater counterparts. Among the long chain fatty acids, polyunsaturated fatty acids

(PUFA) such as linoleic acid (18:2n6), linolenic acid (18:3n3), eicosapentaenoic acid

(20:5n3) (EPA) and docosahexaenoic acid (22:6n3) (DHA) are essential for growth,


85

survival and good feed conversion ratio for P. monodon and other penaeid shrimps. The

n3 fatty acids are more essential than the n6 acids. The fatty acids, EPA and DHA, which

are known as highly unsaturated fatty acids (HUFA) of n3 series, are particularly

important. Quantitatively EPA and DHA are needed at 0.5% and 1.0% in the diet of larvae

and juvenile shrimp. Freshwater fish show requirement for n6 and n3 essential fatty acids

(EFA), whereas marine fish show requirement of n3 and also HUFA. Studies in

Fenneropenaeus indicus have shown that oils rich in PUFA such as fish (sardine) oil,

squid oil and prawn head oil produce superior growth when incorporated in its diet. These

oils are rich in HUFA. Marine fish oils are rich dietary source of n-3 series while plant oils

are rich in n-6 fatty acids.

7.2.2.2. Phospholipids

Shrimps require phospholipids for growth, moulting, metamorphosis and maturation.

Lipids of squid, clam, shrimp, fish and polychaetes are excellent natural sources of

phospholipids. The phospholipids, phosphatidylcholine (lecithin) is essentially required in

the diet of shrimp for fast growth and good survival. Soya lecithin is a good source of

phospholipid for shrimps. It is required at 2% level in the diet. Development and survival

of larvae is significantly improved when the diet contains lecithin. Phospholipids are

found to be involved in the transport of lipid, especially steroids in haemolymph.

7.2.2.3. Steroids

Shrimps grow through the process called moulting and steroid hormones called, ecdysones

are responsible for moulting. To synthesize these hormones, the steroid cholesterol is

required in the diet. Shrimps are not capable of synthesizing cholesterol in their body and

hence must be supplied through diet. The requirement of cholesterol in shrimp diet was

shown to vary from 0.5% to 1.0%. Cholesterol is not essential for finfishes. Many natural

feed ingredients, such as prawn head waste and squid are good sources of cholesterol,

which can be included in the feed formulations.

7.2.3. Carbohydrates requirement

The carbohydrate most commonly found in fish feed is starch, a polymer of glucose. Raw

starch in grain and other plant products is generally poorly digested by fish. Cooking of

the starch during pelleting or extrusion, however, greatly improves its digestibility for fish.

However, even if the starch is digestible, fish only appear to be able to utilize a small

amount effectively. Carbohydrates only represent a minor source of energy for fish. A


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certain amount of starch or other carbohydrates (e.g., lactose, hemicellulose) is,

nevertheless, required to achieve proper physical characteristic of the feed. The nutritional

value of carbohydrates varies among fish. Freshwater and warm water species are

generally able to utilize higher levels of dietary carbohydrates than cold water and marine

species. Carnivorous fishes require less dietary carbohydrates level (< 20%). Omnivorous

and herbivorous fishes require high level of carbohydrates (40–45%). Carnivorous fish

have poor ability to digest carbohydrates due to low amount of amylase produced. The

quantitative requirement of carbohydrate in the diet of shrimp is related to dietary protein

and lipid levels. Depending upon the total energy content required in the diet,

carbohydrate can be used from 10–40% level. Corn flour, wheat flour, tapioca flour and

other grain flours are good sources of starch in shrimp feeds.

7.2.4. Vitamin and mineral requirement

Micro-nutrient such as vitamins and minerals significantly influence the growth and

survival of fish and shrimp and these cannot be synthesized by these organisms. Even

though, some vitamins such as niacin can be synthesized by number of animals, they are

typically insufficient to meet physiological demand. Most of the vertebrates and some

invertebrates are capable of synthesizing vitamin C (ascorbic acid) from glucose due to

presence of enzyme gulonolactone oxidase, whereas many finfishes and shellfishes cannot

synthesize vitamin C due to absence of this enzyme. „Black death‟ in shrimp is a classical

symptom of vitamin C deficiency characterised by melanised haemocytic lesions

distributed throughout the collagenous tissue. Hence, supplementation of vitamins and

minerals become necessary for most aquatic organisms. The vitamin requirement depends

on various factors such as size, age, growth rate, water temperature, composition of diets

and environmental stress. Unlike higher animals, the recommended doses of vitamins for

aquatic animals are higher, as many vitamins lost during the process of feed manufacture

and also due to leaching. Vitamin deficiency symptoms in fish and shellfish are non-

specific unlike in mammals. There are four fat soluble (A, D, E and K) and 11 water

soluble (B and C) vitamins required by various organisms. In crustaceans, there is a wide

fluctuation in vitamin requirement studies and hence no standard vitamin premix has been

evolved like in fishes and other vertebrates.


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Table: Dietary vitamin requirements (mg/ kg diet unless specified) for finfish and

shellfish.

Vitamin Finfish Shellfish

Vitamin A(IU) 2000–5000 30000–50000

Vitamin D (IU) 1000–2400 2000–2400

Vitamin E 30–100 30–40

Vitamin K 10–1000 4–6

Thiamine 1–15 15–30

Riboflavin 7–30 15–60

Pantothenic acid 25–50 60–120

Pyridoxine 3–20 60–120

Niacin 120–200 60–120

Folic acid 6–10 6–10

Cyanocobalamine 0.01–0.02 0.01–0.02

Choline 2500–3000 600–800

Ascorbic acid 50–70 8000–10000

Fish and shellfish can absorb minerals directly from aquatic environment through

gills and body surfaces or by drinking. Hence, dietary requirement of minerals is largely

dependent on mineral concentration of the aquatic environment. About 20 inorganic

elements (macro and micro) are required to meet the metabolic and structural functions in

the body of animals. Aquatic organisms regulate the mineral needs through dietary source

and also through internal regulatory mechanisms in kidneys and gills. In saline waters,

calcium (Ca) is abundant, which is absorbed by most aquatic animals. Since the

availability of phosphorus (P) through water medium is poor, P should be made available

through diet. Usually the preferred Ca:P ratio is 1:1 in feeds of aquatic species. Mono and

dicalcium phosphate contain more available P than tricalcium phosphate. Incorporation of

P should be very discrete in fish and shellfish feeds, as most of it gets excreted leading to


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eutrophication. Dietary requirement of P ranges from 0.5–0.9% in fishes and 1–2% in

shellfishes. Requirement of magnesium (Mg) in shrimp and fish ranges between 0.04–

0.3%. Requirement of zinc (Zn) ranges from 15–30 mg/ kg diet for fishes and 80–120 mg/

kg diet for shellfishes. Requirement of iron (Fe) ranges from 150–200 mg/ kg diet for

fishes and 60–100 mg/ kg diet for shrimps. Major deficiency symptoms of manganese

(Mn) in fishes are cataracts and abnormal curvature of the backbone and malformation of

tail. A dietary supplementation of 11–13 mg/ kg restores normal growth in fishes. In

shrimps, the requirement goes up to 40–60 mg/ kg which may be due to periodic ecdysis.

Trace minerals like copper (Cu), cobalt (Co), selenium (Se), iodine (I) and

chromium (Cr) have some role in general upkeep of the organism. Their dietary

incorporation enhances growth and survival. Copper is needed by crustaceans because of

haemocyanin. Optimum dietary level of Cu ranges from 40–60 ppm and it was also

observed that omission of Cu from the diet was not detrimental as, crustaceans are able to

meet their demands from seawater.

7.3. Feed formulation

Before proceeding with formulating a feed, the ingredients are to be selected from

available sources. No single ingredient can be expected to provide the entire nutrient

requirement. Each ingredient in the diet should be included for a specific reason i.e., either

to supply a specific nutrient or physical property to the diet. Formulation of a feed by the

nutritionist is only the beginning of a process that ends when the feed is finally consumed.

Feed formulation is essentially a recipe making process keeping in mind the nutritional

requirement of particular species, palatability and growth promoting ability of that feed.

These objectives can be achieved by judicious selection of feed ingredients, mixing them

in proper proportion and presenting them in a most acceptable form.

The basic technique used in ingredient selection is through “Least cost” or “Best

buy” calculations.

7.3.1. Least-cost or best-buy technique

The price of the feedstuffs used in diet formulations must be considered to formulate a

cost-efficient diet. Feedstuffs can be compared with one another on the basis of cost per

unit of protein, energy, or amino acid. The cost of protein is often the greatest part of the

cost of a fish diet. Therefore, substantial savings can be made by using best-buy technique

to determinate least expensive protein supplement. When several feedstuffs are available


89

to supply a particular nutrient then it is useful to calculate the cost per unit of nutrient from

each of the ingredients and compare.

Example: If soybean cake costs Rs.16/ kg and contains 45% protein-

Cost/ kg protein= 16/0.45= Rs.35.56

Ground nut cake costs Rs.13/ kg and contains 40% protein

Cost/ kg protein= 13/0.40= Rs.32.50

Thus, although soybean cake contains higher level of protein, the cost per kg

protein from ground nut cake is less. Therefore, ground nut cake is a better buy. To

compare feedstuffs on the basis of cost per unit of an amino acid, one can calculate the

best buy in the same way as before.

For example, sesame oil cake which has twice as much methionine content as does

groundnut cake on a per unit protein basis would be a more attractive buy at comparable

prices.

These kinds of comparisons are only valid if the nutrient in one feedstuff is as

valuable or available to the animals as the same nutrient in another feed. Such

comparisons should be made whenever prices charge.

7.3.2. Balancing nutrient levels

In most animal diets, protein is the most expensive portion and is usually the first nutrient

that is computed in diet formulation. The energy level of the diet is then adjusted to the

desired level by addition of high energy supplements which are less expensive than protein

supplements. The square method is an easy way to determine the proper dietary

proportions of high and low protein feedstuffs to add to a feed to meet the dietary

requirement of the animal to be fed. The protein in the diet can be adjusted by following

Pearson‟s square method. For example, to prepare a diet with 38% protein using soybean

meal (CP: 45%), fish meal (CP: 55%) and wheat flour (CP: 10 %), ingredients are to be

divided into two groups, Group A- protein rich ingredients (soybean meal and fish meal)

and Group B- energy rich ingredient (wheat flour). Mean protein percent has to be

calculated from both the groups. A square is constructed first and the names of the feed

groups are written on the two left corners along with the mean protein content of each

group assuming that under each group ingredients are mixed in an equal proportion. The

required protein level of feed is written in the middle of the square. Next, the protein level


90

of the feed is subtracted from that of the ingredients and answer is placed ignoring the

positive or negative sign.

Group A (CP-50%) Group A 28

Group B (Wheat flour-CP-10%) Group B 12

-----------

40

Add the figures on the right hand side of the square, i.e., 28+12= 40

Now, to make the feed with 38% protein, we should mix

Group A ingredients- 28/40 × 100 = 70%

So, Soybean meal to be mixed- 70/2= 35%

Fish meal to be mixed- 70/2 = 35%

Group B ingredient, i.e wheat flour - 12/40 × 100 = 30%

The square method is helpful to novice feed formulators because it can get them

started in diet formulation without the need to resort to trial and error. The square method

can also be used to calculate the proportion of feed stuffs to mix together to achieve a

desired dietary energy level as well as a crude protein level. The square method cannot be

used to simultaneously solve for both crude protein level and ME level.

7.3.3. Linear programming

The mathematical technique available to nutritionists for selecting the best combination of

feed ingredients to formulate diets at the least possible cost is linear programming.

Information necessary for feed formulation using linear programming includes:

i) Nutrient content and DE or ME of ingredients;

ii) Unit price of feedstuffs including vitamin and mineral mixtures;

iii) Any other additives to be used in the feed; and

Soybean meal : Fish meal (1:1),

Mean protein= (45+55)/2= 50%

38


91

iv) Minimum and maximum restriction on the amounts of each ingredient in the feed.

Least-cost linear programming software for diet formulation is readily available,

the price varying with the sophistication required. A commonly used spreadsheet a such as

Lotus 1-2-3 can also be utilized for formulating feed, incorporating a smaller number of

variables. It should be noted that least-cost feed formulation is not always practical for

small scale aquaculturists using on-farm feed manufacture facilities where are the choice

of ingredients available is limited.

7.3.4. Quadratic programming formulation

Nutrient requirements used in linear programming feed formulation are fixed usually for

maximum rate of growth. This may not be the best decision from economic point of view.

Nutrient constraints may be relaxed to bring down feed cost while still achieving

acceptable lower growth. Quadratic programming takes into account the growth response

within a range of nutrient constraint. Therefore, good understandings of biological

response functions from actual feeding trials are essential in the use of quadratic

programming. For example, it was reported that inclusion level of arginine could be

reduced by 20% with only a 5% likely reduction of growth of Nile tilapia.

7.4. Feed management in fish culture systems

Feed management means use of feed in such a way that utilization of feed is optimum;

wastage is minimum thereby negligible impact on environment, achieving best feed

conversion ratio and maximum growth and production of fish and shrimp. A very good

quality feed can produce poor result if the feed management is poor, whereas, a moderate

feed can produce very good results under good feed management.

The foremost critical factor is selection of appropriate feeds and planning of

optimal feeding regimens. Suitable feed should fulfill the nutritional requirements of

species under culture. Proteins, lipids, carbohydrates, vitamins, minerals and water are the

six major classes of nutrients, which are used for building, maintenance of tissues and

supply of energy. The requirement for these nutrients varies depending on the species

according to their feeding habit, habitat in which they live in and the stage in their life

cycle. Our aim should, therefore, be to produce nutritionally balanced feed with optimum

protein energy ratio. It should also ensure that nutrients are not lost in water during the

feeding process. Therefore, aquaculture feeds of different formulations are processed

using the special technologies to ensure the diet remain intact in water before ingestion,


92

and that nutrients are prevented from dissolving. These general categories of feeds used in

aquaculture are wet feeds with moisture contents of 50–70%, semi moist formulated feed

with moisture contents of 20–40% and dry pelleted feeds with moisture contents of less

than 10%. Since problems are associated with the distribution, handling, utilization,

storage and quality of wet feeds and moist feeds, more and more dry feeds are

manufactured either by steam pelleting or by extrusion pelleting. Advances in fish feeds

and nutritional studies mean that many commercial feeds satisfying a wide range of

options are now available.

Following points should be strictly followed while feeding the fish for maintaining

good pond hygiene and to reduce wastage of feed and to avoid accumulation in pond

bottom.

i) Pond biomass should be assessed regularly and ration should be offered as per

biomass of the pond.

ii) Time and method of feeding should be proper.

7.4.1. Ration size

Size of daily food ration, frequency and timing of meals are the key factors influencing

growth and feed conversion. Hence, optimal feeding regimens must be determined as per

the feeding behaviour, appetite and functioning of the digestive systems and the various

specific chemical substances, which act as feeding stimulants for fishes. Fish lose weight

when their food intake falls below that required for maintenance. When ration size

increases, growth rate increases. Generally, method of calculating daily ration is based on

the body weight of fish. The quantity of ration varies from 100% of body weight for larvae

and fry, and gradually reduced to 50, 20, 10, 5 and 2–3% as the fish/ shrimp grows

marketable size. Ration size is also estimated by various methods using feeding charts,

feed equations, growth prediction and check tray etc. Besides the food ration size, optimal

food particle size also affects the growth and feed conversion efficiency. Large fish can

ingest small particles, but it requires more energy to capture the required equivalent

weight or smaller food particles. This results in measurable reduction in food conversion

efficiency. Attention should also be given to influences of feed shapes, colours and

textures of pellets on ingestion rates.


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7.4.2. Feeding methods

Production of high quality fish at least-cost depends on an effective feeding method.

Various techniques exist, from hand feeding to mechanized feeding. They depend on

diverse range of factors such as labour costs, scale of farming, species under farming, type

of holding system and hatchery or grow-out systems. Often farmers use a combination

feeding methods such as hand feeding to mechanized feeding. Feed bag suspended at

different places in ponds is most common method of feeding to the fish. In mechanical

feeding system, demand feeder is used in which fish approaches to the feeder for its feed

requirements when they feel hungry. It was observed that fish quickly learn how to obtain

feed. The growth of fish is good with best FCR and minimum wastage of feed in self-

demand feeding system. This method works best with finfish farming. A reliable and least-

cost feeding system should ensure the effective distribution and spread of adequate feeds

in aquaculture ponds.

7.4.3. Schedule and frequency of feeding

Total feed required in a day should not be fed at a time. Scheduling and frequency of

feeding greatly help in successful feed management. Time schedule for feeding the fish

may be fixed in such a way that larger ration may be given when the fish is expected to be

most hungry. If night feeding is limited, the morning feeding should have larger ration.

There should be a minimum of three time schedules of feeding in a day- morning, noon

and evening. Species which are having nocturnal feeding habit should get comparatively

larger portion of the ration in the evening or night. Frequent feeding of small portion of

ration helps in better utilization of the feed and thereby leads to efficient FCR. There must

also be a mechanism in each case to monitor the feed consumption and offering of next

dose of feed should be regulated on basis of consumption from the previous feed offered.

7.4.4. Handling and storage of feeds

Optimizing handling and storage procedures on farms is an essential component of good

management practice. High quality feed can readily spoil and denature if stored under

inadequate conditions or for too long a period. Incorrectly stored feeds may not only be

unappetizing to fish or lacking in essential nutrients but also may contain toxic and

antinutritional factors. This can lead to abnormal behaviour, poor feeding response and

growth. Hence, different feed types such as wet feeds, moist feeds and dry feeds must be

handled and stored under appropriate conditions.


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7.4.5. Water quality

The interrelationships between feeding and water quality in aquaculture is complex. By

providing optimal species-specific requirements such as temperature, dissolved oxygen,

pH and salinity, adequate feeding to satiation, improved growth and survival can be

ensured. When the water quality parameters fall below optimal levels, feeding and growth

will be impaired and the species under culture will be stressed. Accumulation of left over

feed together with excretory products is associated with high BOD, NH3, H2S, CH4 and

harmful effects of eutrophication. This is a critical issue in management, since effluent

quality can be linked directly to feeds and feeding practices and is regulated under water

pollution control laws in many countries. Thus, feeding regimes should be designed to

minimize nutrient loss and faecal output and to maximize nutrient retention and health

status of the cultured fishes. Judicious feed management is an important factor in

achieving good feed efficiency and reducing wastage. Selecting feeds, which are freshly

prepared, quality assured and proven with best potential FCR could reduce waste

production. Poor quality and water stable feeds, which have lost their nutritional potency

and are poorly accepted by the fish, should be rejected. Appropriate particle size of the

feed should be designed for a particular stage. The ration size and feeding schedules

should be regulated with reference to feeding guides, response of fish and environmental

conditions.


95

Advances in Mud Crab Farming

P.S. Shyne Anand, C.P. Balasubramanian,

Christina L.* and T.K. Ghoshal*


*Kakdwip Research Centre of ICAR-CIBA, Kakdwip, West Bengal

8.1. Introduction

Mud crabs or mangrove crabs are widely distributed in coastal waters, lagoons,

brackishwaters lakes, estuaries and intertidal swampy or mangrove areas available along

the coastal lines of tropical and subtropical countries. They are much sought-after seafood

commodities by virtue of delicacy, export demand and high market price. Mud crabs

belonging to genus Scylla spp., are commercially important and fetch high value in export

market. Among the four species of mud crabs, Scylla serrata, S. olivacea, S.

tranquebarica and S. paramamosain, the largest and most broadly distributed mud crab is

S. serrata. In India, most widely distributed species are green mud crab, S. serrate and

orange mud crab S. olivacea (Balasubramanian et al., 2014).

Mud crabs are the fastest growing species among all commercially farmed

crustaceans with average weekly gain of 10 g compared to 2 g/week of tiger shrimp.

Among these, the fastest growing S. serrata attains a maximum carapace size of 280 mm

and 3.5 kg recording even 14–28 g/week weight gain. In the light of virus affected coastal

ponds, mud crab farming forms an excellent mean of diversification of brackishwater

aquaculture. Various type of crab farming techniques like crab fattening, grow-out

rearing, cage culture, mangrove pen culture etc. are widely being practiced in Indo-Pacific

and many South East Asian countries like the Philippines, Taiwan etc. Scientific crab

culture is getting momentum due to its high value in the live export market (mainly South

East Asian countries) and minimum disease risk noticed during the culture period.

Among the two commercially important mud crabs, S. serrata and S. olivacea

cultured in the country, the former one is preferred due to its fastest growth rate, late

maturity, less aggressive behaviour with minimum burrowing nature and minimum

damages it causes to the bund and fencing arrangement of the cultured ponds compared to

8


96

later one. ICAR- Central Institute of Brackishwater Aquaculture, Chennai has

standardized the hatchery seed production cycle of S. serrata in late 1990s. A package of

technology for mud crab culture as well as for production of seed in hatchery available for

commercialization, and this envisages the scope for the large scale development of crab

farming in the country.

8.2. Brief biology

Mud crabs belonging to the family portunidae can be recognized by the presence of

flattened 5th

pair of swimming legs. Apart from the genus Scylla, Portunus and Charybdis

are other commercially important portunid crabs. After mating, the gravid female mud

1. S. serrata 2. S. olivacea


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crabs migrate from estuarine areas to the inshore sea for spawning. The number of eggs

carried by S. serrata is about 2 to 5.0 million and by S. olivacea is 1 to 3 million. The eggs

hatch out in the sea and larvae undergo metamorphosis and later they migrate to the

estuarine systems. There are five zoeal stages which undergo five moulting to reach

megalopa stage in 16–18 days interval, and megalopa changes in to crab instar in 7–8 days

period in optimum salinity (27–28 ppt). Mud crab farming includes nursery rearing, grow-

out culture and crab fattening.

8.3. Nursery rearing

Nursery rearing involves rearing of megalopa to crab instar in two phases namely up to 3 g

in hapa and 3–25 g in nursery ponds. In nursery rearing first phase, megalopa or early

crablets can be stocked in nylon net hapa (3×2×1) fixed in open brackishwater ponds or

nursery earthen ponds. In order to reduce cannibalism, seaweed bunches or nylon threads

or net bundles can be provided in nursery ponds for refuge. Early juveniles can be fed with

calm meat or minced meat at 200–50% of biomass. The average expected survival in the

nursery rearing system is up to 60%. In nursery rearing phase II, the crablets of 3 g size

are reared up to crab juveniles at 2–20 nos./m2 in fenced nursery ponds using fresh feed at

10% of body weight.

8.4. Grow-out culture techniques

Grow-out crab culture can be broadly divided in to two major techniques like crab

fattening and grow-out farming. In grow-out techniques, nursery reared crab juveniles

(30–50 g) are reared for a 6–7 month period to attain marketable size of 500 g, whereas

fattening refers to the holding of water crabs for short duration to acquire maximum

marketable traits to obtain better economic returns.

Male S. serrata Female S. serrata


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8.4.1. Grow-out ponds

Mud crab grow-out culture can be carried out in any coastal ponds or abandoned shrimp

ponds with little modification. Since mud crabs can crawl out of the ponds, it is imperative

to provide crab fencing around the ponds to avoid the escape of crabs. As mud crabs are

highly cannibalistic in nature, hideouts like PVC pipes need to be provided to protect the

crabs during moulting and to increase survival. Construction of dry raised feeding

platforms or mounds within the ponds are also appreciable as it can mimic their periodic

exposure that occurs in the natural system. These platforms can also act as the feeding

zones for the crabs. In grow-out system mud crabs are generally stocked at 0.5–1.5

nos./m2. Mud crabs can be fed with formulated feed or trash fish or locally available

mollscan meat at 8–2% of body weight. A scientifically managed grow-out rearing pond

can yield up to 2 ton/ha with an estimated survival of 60%.

8.4.2. Mangrove pens

Mangrove zones can be used as an excellent area for mud crab farming as it acts as the

native habitat of mud crabs. Mangrove pens can be designed to retain mud crab in a

specific area of mangrove where crabs can be fed and growth can be periodically

measured and managed. Height of the pens must be higher than the height of the

maximum high tide level to prevent the escape of crabs. Mangrove based mud crab

systems can add value to mangrove ecosystem and can complement conservation

measures to maintain mangrove ecosystem.

8.4.3. Polyculture

As mud crabs cannot catch fast moving preys like shrimps or finfishes, polyculture of mud

crab with finfishes or shrimp has tremendous scope to increase the economic return of the

Crab grow-out pond Crab grow-out cages


99

culture. Polyculture of mud crabs with milk fish or mullets and tiger shrimps or seaweeds

can yield up to 2.5–3 ton/ha in six month culture period. Polyculture of mud crabs is being

widely practiced in India and South East Asian countries like Tawan, Vietnam, China etc.

8.4.4. Monosex culture

Monosex culture are getting momentum now-a-days as crabs are sexually differentiated

and stocking with monosex culture minimizes post-harvest processing measure and

aggressive behaviour between crabs associated with sexual maturity. Studies reveal that

monosex culture of female or male increases the survival rate compared to mixed sex

culture.

8.5. Crab fattening

Crab fattening is the technique where water crabs or newly moulted are held for a period

of few weeks until they are full of meat and ready to market. Generally floating cages or

tanks cans be used for fattening. Fattening is widely followed in Thailand, Taiwan,

Malaysia and Indonesia. Potential grounds adjacent to productive brackishwater lakes can

be used for the expansion of this profitable venture. Carb fattening can be carried out at

high densities provided with good quality of water, optimum feed management and health

management. Flow through systems and recirculatory land based aquaculture systems are

other sophisticated mud crab fattening systems.

8.6. Silviculture and canal based systems

Damaged or degraded mangrove systems can be countered through mangrove

reforestation in coastal zones and canals systems. These areas provide opportunity for low

density culture of mud crabs through proper fencing and other management measures.

These areas also provide scope for community based mud crab farming system. Potential

mangrove ecosystem in the country provides scope for this silviculture based mudcrab

farming.

8.7. Cellular system

In cellular system, crabs are held individually in the containers or cells for the culture of

soft shell crabs. In this system, small crab (30–120 g) is held in isolation until it moults, at

which point they are chilled or frozen before shell harden. The crabs are culturde for a

week until they moult.


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8.8. Conclusion

Major disadvantage of mud crab farming is the long grow-out period extending up to a

almost an year, including nursery and hatchery phase. In order to optimize the economy

of farming, novel approach of three tire farming system comprising nursery, middle grow-

out and final grow-out phases developed by ICAR-CIBA, Chennai can produce a single

live crab of 1 kg which fetches a market value of about Rs.1000/-.

Further readings

Keenan, C. P, Davie, P. J. F. and Mann D. L., 1998. A revision of genus Scylla de

Han. 1833 (Crustacea: Decapoda: Brachyura: Portunidae). Raffles Bulletin of Zoology

46: 217-245.

Balasubramanian CP, and Gopal C., 2014. Diversification of coastal aquaculture-

mudcrab culture. Training manual on health management practices of finfish and

shellfishes of brackishwater environment. CIBA Special Publication. pp: 38-47.

Balasubramanian CP, Cubelio SS, Mohanlal DL, Ponniah AG, Kumar R, Bineesh

KK, Ravichandran P, Gopalakrishnan A, Mandal A, Jena JK., 2014. DNA sequence

information resolves taxonomic ambiguity of the common mud crab species (Genus

Scylla) in Indian waters Mitochondrial DNA.

Shelley C and Lovatelli A., 2011. Mudcrab Aquaculture-A practical Manual FAO-

Fisheries and aquaculture technical paper-547, FAO, Rome, 100 pp, C 2014.

http://www.ncbi.nlm.nih.gov/pubmed/?term=Balasubramanian%20CP%5BAuthor%5D&cauthor=true&cauthor_uid=24660913

http://www.ncbi.nlm.nih.gov/pubmed/?term=Balasubramanian%20CP%5BAuthor%5D&cauthor=true&cauthor_uid=24660913

http://www.ncbi.nlm.nih.gov/pubmed/?term=Cubelio%20SS%5BAuthor%5D&cauthor=true&cauthor_uid=24660913

http://www.ncbi.nlm.nih.gov/pubmed/?term=Mohanlal%20DL%5BAuthor%5D&cauthor=true&cauthor_uid=24660913

http://www.ncbi.nlm.nih.gov/pubmed/?term=Ponniah%20AG%5BAuthor%5D&cauthor=true&cauthor_uid=24660913

http://www.ncbi.nlm.nih.gov/pubmed/?term=Kumar%20R%5BAuthor%5D&cauthor=true&cauthor_uid=24660913

http://www.ncbi.nlm.nih.gov/pubmed/?term=Bineesh%20KK%5BAuthor%5D&cauthor=true&cauthor_uid=24660913

http://www.ncbi.nlm.nih.gov/pubmed/?term=Bineesh%20KK%5BAuthor%5D&cauthor=true&cauthor_uid=24660913

http://www.ncbi.nlm.nih.gov/pubmed/?term=Ravichandran%20P%5BAuthor%5D&cauthor=true&cauthor_uid=24660913

http://www.ncbi.nlm.nih.gov/pubmed/?term=Gopalakrishnan%20A%5BAuthor%5D&cauthor=true&cauthor_uid=24660913

http://www.ncbi.nlm.nih.gov/pubmed/?term=Mandal%20A%5BAuthor%5D&cauthor=true&cauthor_uid=24660913

http://www.ncbi.nlm.nih.gov/pubmed/?term=Jena%20JK%5BAuthor%5D&cauthor=true&cauthor_uid=24660913


101

Concept and Scope of Organic Brackishwater

Aquafarming

Akshaya Panigrahi, P.S. Shyne Anand and C.P. Balasubramanian


9.1. Introduction

Organic farming restricts the use of artificial chemical fertilizers and pesticides,

chemotherapeutic medicines including antibiotics and encourages utilization of natural

nutrients, probiotics and bioremedial measures. The first „scientific‟ approach to organic

farming can be quoted back to the “Later Vedic Period”, 1000 BC to 600 BC (Randhawa,

1986; Pereira, 1993). The essence is to live in partnership with, rather than exploit, nature.

This knowledge system is even today present with millions of Indian farmers as its

practitioners and now with the increasing organic market, there is an organic revolution

brewing throughout the country. These systems are based on specific standards precisely

formulated for food production and aim at achieving agro ecosystems, which are socially

and ecologically sustainable. To reverse the depleting productivity, biodiversity,

mangrove and other habitat, organic aquafarming is the best answer. Coming to

brackishwater aquaculture, organic shrimp farming gives a distinct orientation to the

disease and environmental concern ridden shrimp farming. Salmon and penaid shrimps are

commercially most important species followed by species like trout and carp, and new

trend of organic production is for organic mussels, algae and integrated multi-trophic

aquaculture (IMTA).

In India, organic aquaculture is in a very nascent stage though it has enormous

potential. The vast resources of bheries, gheries and pokkali fields of India where

traditional systems are being followed can qualify for organic status with certification and

traceability marks. The development of aquaculture system as model of environmental

stewardship is possible through organic practices and system. India could emerge as a

major player in organic production and exports in the world market. The country has

immense potential in this sector and the government has put in place an accreditation

system as per the National Standards for Organic Products, which will enjoy reciprocal

approval from other international organic programmes. MPEDA introduced an attractive

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102

assistance package that provides farmers 50% of the cost of procuring organic seed and

feed, as well as certification.

9.2. Main features of organic farming

Organic food production promotes biodiversity, biological cycles and biological

activity.

Organic farmers aim to manage food production as an integrated, whole system.

Organic food production encourages the maintenance and sustainability of this

system by restricting the introduction of harmful substances and practices that

reduce or alter the connectedness of the system‟s components.

Organic farming severely restricts the use of artificial chemical fertilizers and

pesticides.

Organic farmers rely on developing a healthy, fertile soil/water.

Genetically modified organisms (GMOs) and products produced from or by GMOs

are incompatible with the concept of organic production and consumers' perception

of organic products.

9.3. Definition

Organic aquaculture is a process of

production of aquatic plants and animals

with the use of only organic inputs in terms

of seed and for the supply of nutrients and

management of disease. However, the

variety of species produced in aquacultural

systems and vast differences in cultural

requirements for finfish, shellfish, molluscs

and aquatic plants add to the complexity of

defining this sector.

Organic aquaculture is a relatively

new field of organic production compared

to organic agriculture, where long

experience exists at the farm level. Given

Fig: the price premium pyramid for natural, hormone and

antibiotic free and organic products

(Source: INFOFISH, 2009)


103

consumers‟ growing interest in organic aquaculture products, further growth in the

conversion of aquaculture units to organic production is likely. This will soon lead to

increased experience and technical knowledge. Certified organic mussels, tiger shrimp,

white shrimp, and tilapia also cultured in countries like Vietnam, Peru, Ecuador, Chile,

New Zealand and Israel.

9.4. Present status

India ranks 33rd

in term of total land under organic cultivation and 88th

in term of the ratio

of agricultural land under organic crops to total farming area. The cultivable land under

organic certification is 0.96 million ha. However, including wild collection area, it

amounts to 3.95 million ha. In 2009-10, the total volume was 44,476 million tons realizing

$116 million registering a 50.31% growth over the previous year. The major products

categories include tea, spices, honey basmati rice, coffee, vegetables, cereals, dry fruits

(walnuts, cashew), sesame seeds and medicinal plants and garments made of organic

cotton.

Aquaculture (the farming of aquatic animals and plants) is expanding at an average

rate of 9% per year since 1970. Global oranic aquaculture production in 2013-14 is around

150,000 tons and global market or organic fish, shellfish and seaweed is expected to

increase further year after year. Organic penaeid shrimp production is around 25,000 tons

(increasing trend). Based on current estimates of certified organic aquaculture production

and an anticipated compound annual growth rate of 30% from 2001 to 2010, it can be

expected that certified organic aquaculture will increase considerably, while still

remaining a small share of total aquaculture production. The global demand for organic

fish and fish products is estimated at over $20 billion (Rs.9 lakh crore). US and Europe,

which are the major organic fish markets, import a major bulk of India's marine fish

products. For India, if the marine shrimp exporter can get 25% of their products labelled

as organic, it will fetch an additional export revenue of Rs.3000 crore annually. Average

price premium for these organic produce is between 20 to 40% on retail price.

In South East Asian countries including India, low input traditional systems are

being followed and these could qualify for organic status with minimum modifications.

The rationale behind raising fish on animal manure becomes apparent when it is realized

that about 72–79% of the nitrogen, 61–87% of the phosphorus and 82–92% of the

potassium in the feed rations fed to animals are recovered in the excreta (Edwards, 1980).


104

The quantities and diversity of certified organic produce being produced remain small,

partly due to the absence of universally accepted standards and accreditation criteria of

organic aquaculture. Though the organic aquaculture is in its nascent stage, with the

guideline in place by National Programme for Organic Production (NPOP), and its

promotion by ICAR institutes and MPEDA, this is being adopted by many farmers.

9.5. Organic certification

Organic certification is a process claim, not a product claim. In other words, organic

standards regulate the practices and materials used to produce an agricultural product. It

does not make any claims about the end product such as nutritional value or food safety;

however, organic producers have to follow the same strict guidelines at the local, state and

federal level that all conventional food producers must follow.

9.5.1. International organic aquaculture standards

Other aquaculture standards have been developed, many still in draft form, throughout the

world. These include Germany‟s Naturland, the UK‟s Soil Association, and Sweden‟s

KRAV standards. The International Federation of Organic Agriculture Movements

(IFOAM), a large umbrella organization, has also drafted organic aquaculture standards.

The NATURLAND (Germany) and presently the EU regulations are more important for

setting standards for organic shrimp production.

9.5.2. National standards for organic production

The standards and procedures have been formulated in harmony with the international

standards such as those of Codex, IFOAM and keeping Indian requirements in mind. The

guideline standard by NPOP under the apex body of APEDA, India is limited to the

production, processing and certification of aquaculture. These standards shall apply to all

aquatic organisms cultured in fresh and brackishwater ponds and open water bodies in

estuaries and sea. Organic producers must submit an organic plan which details all their

management practices. They must maintain records to preserve the identity of the animals.

They must document all of the feed sources and health care inputs and practices.

9.6. Important points for organic aquaculture

Organic aquaculture certification under NPOP developed standard applies to all aquatic

organisms cultured in fresh and brackishwater ponds and open water bodies in estuaries

and sea (Black tiger shrimps, Indian major carps, fresh water prawns and bivalves). Under


105

the framework given by IFOAM, ICAR-CIBA and other institutes are taking up the

organic farming defining the principles and practices broadly under the following heads.

9.6.1. Conversion period

Conversion period shall be considered from the date of registration under a certification

agency until 100% compliance to the standards is met. The length of the conversion period

would vary depending on the species, method of production, location and local conditions.

Generally, for drainable systems where cleaning and disinfection is carried out, the

conversion period shall be 6 months/ one crop whichever is longer and in case of drainable

and fallowed, the conversion period will be for 12 months. In case of non-drainable

systems which cannot be disinfected, the conversion period shall be 24 months. In case of

open water farming, the conversion period shall be considered as 3 months.

9.6.2. Aquatic production systems

In selecting the site, ensure that the surrounding aquatic and terrestrial ecosystems are not

adversely affected through modifications brought about by building the farm or through

release of farm wastes.

i) In developing new farms or expanding existing farms ensure that vegetation is protected.

Care is taken so that there is at least 30% natural vegetation by maintaining natural

vegetation or re-planted.

ii) The release of nutrients and waste into the surrounding aquatic ecosystem is minimized

and the water quality standards of released water are in conformity with those given by

Coastal Aquaculture Authority (CAA).

iii) The aquatic production systems are placed at an appropriate distance from any

contamination sources to ensure that there is chance of contamination of incoming

water. The quality of water with respect to contaminants to be checked before selecting

the site.

iv) Materials and substances used in the construction should not cause damage to

environment or organisms.

v) Only environment friendly and allowed substances should be used for the organic

production system.

vi) The production unit should only culture the specified stock neither allowing unwanted

entry of other animals nor escape of the stock from the system.


106

vii) Inputs in terms of the fertilizers and feeds should be conducive to the organic way of

farming.

viii) Use of ground water for the culture purpose should be avoided.

ix) The site should meet the criteria of the „approved‟ in terms of general water quality,

trace metal contents, bio-toxin levels and microbial load as per the specification.

x) Organic will act as a template for a new sustainable farming system where production

and conservation can be achieved in a holistic manner.

xi) Cooperation with neighboring farmers for effective management of the production

system and environment.

xii) The water quality must be conducive for the species to live in (within the optimum range-

pH, salinity, Oxygen, temperature, nitrogen fractions, BOD etc.) during the production

cycle.

9.6.3. Breeds and breeding of aquatic animals

i) Aquatic animal breeds and the breeding techniques proper for the species, environment

and local conditions should be utilized/ addressed.

ii) As far as possible the appropriate natural breeding behavior should be adopted giving no

room for the inbreeding depression.

iii) In case of tiger shrimp where still the induced maturation is largely dependent on the eye

stalk ablation. This practice will be allowed up to 2015 by when it is expected that the on-

going R and D programmes in the country would lead to the development of technology

for natural spawning of captive brood stocks on commercial scale. For carps and Fresh

water prawns, the maximum percentage of non-organically produced juveniles allowed

to be introduced to the farm shall be 80% by 2012, 50% by 2013 and 0% by 2015.

Collection of natural brood stock for tiger shrimp is permitted until domesticated brood

stock is commercially available in the country

iv) Any kind of artificially induced poplyploidy, genetically engineered or monosex stock is

to be rejected.

v) Also the synthetic hormone application for artificial propagation is not accepted for

organic aquaculture practice.

vi) To avoid stress to the animal, thermal manipulation for accelerated larval


107

development/growth or maturation, beyond natural range is prohibited in hatcheries.

vii) Eggs and their fertilization are monitored to ensure healthy seed.

viii) The disinfection and cleaning in the hatchery should not have any impact on the

surrounding environment.

ix) Monitoring and recording the water quality parameters and if possible the environmental

impact assessment.

x) Endemic species is preferred over exotic species. If exotic species are to be selected, their

impact on endemic species and environment should be ascertained. Like in case of

Litopenaeus vannamei introduction risk analysis was the first and foremost thing done

before its introduction.

xi) Collection of wild seed for selective stocking is prohibited (except for bivalves). In

traditional farming systems passive entry of wild seeds is allowed as it ensures species

diversity in farming operation.

xii) A hatchery may convert in full or partial for the production of organic seed. The

hatchery shall maintain organically and conventionally produced seed in separate units

and maintain adequate records to show the separation.

9.6.4. Organic culture practice

i) Stocking density to be limited so as not to compromise with the animal wellbeing,

ecological capacity of the site and species-specific physiological need and animal

behaviour. For shrimp farming, the stocking density should be up to 6 nos./m2 and

biomass in the pond shall not exceed 1500 kg/ha/crop and for scampi the stocking density

up to 2.5 nos./m2 and biomass in the pond shall not exceed 800 kg/ha/crop.

EU organic regulation allows a maximum on farm stocking densities and production

limits - Seeding: maximum 22 post larvae/m2; Maximum instantaneous biomass: 240

g/m2

for penaeid shrimp.

ii) For carp fry and fingerlings production in nursery, the stocking density should be up to 2

million spawn/ha (200 nos./m2) and 0.1 million fry/ha (10 nos./ m

2), respectively.

iii) For grow-out production of carps, stocking density up to 4000 fingerlings/ha (0.4 no./ m2)

may be followed and the maximum biomass should not exceed 3 tonnes/ha at any point

of time. In case of carp farming, polyculture of compatible carp species is preferred over


108

monoculture in order to utilize the ecological niche effectively.

Tropical fresh/ brackishwater fish: milkfish (Chanos chanos), tilapia (Oreochromis spp.),

siamese catfish (Pangasius spp.) can be organically grown in production systems like

ponds and net cages. Similarly, organic production of sea bass, sea bream, mullets (Liza,

Mugil) and eel (Anguilla spp.) in earthen ponds of tidal areas and costal lagoons.

9.6.5. Aquatic animal nutrition

i) The natural feeding behaviour should be explored meeting the nutritional and dietary

need of the species and its life stages with good quality organic feed beyond the portion

met by the natural productivity.

ii) All organic aquaculture system must primarily thrust on organic feed; however, the non-

organic feed is allowed only if organic feed is not accessible within a time frame.

iii) All agricultural products including plant protein etc. are organic and can be incorporated;

the aquatic animal protein and oil being non-organic can only be encouraged if it is

harvested from verifiable sustainable sources including wild marine product or by-

product from human consumption.

iv) Non-organic feed is to be specified and time limited.

v) All kind of supplements for vitamin, minerals are to be supplied through natural sources

unless insufficient.

vi) The synthetic amino acids and amino acid isolates, nitrogenous compounds, binders and

urea, growth hormone and stimulants, solvent extracted ingredients, slaughter from same

species, appetizers, preservatives and colours should never be incorporated in the feed.

vii) Any kind of GMO or derivative of them should not be incorporated.

9.6.6. Aquatic animal health and welfare

i) Production unit to be designed to keep up quality environment and most befitting with the

natural behaviour of the stock.

ii) Chemotherapeutics with allopathic veterinary drugs like formalin, BKC and antibiotics

are to be prohibited.

iii) Probiotics and yeast based organic preparations may be used for maintaining better pond

environment and to control pathogens.


109

iv) During harvest sodium metabisulphite use is prohibited, chill killing and use of ascorbic

acid to stop discolouration can be practiced.

9.7. Organic shrimp farming technology: developed by ICAR-CIBA

CIBA has developed and demonstrated some system of farming based on Low Input

Sustainable Aquaculture (LISA); like improved traditional system, Low input low cost

system, periphyton based farming system, brackishwater polyculture system and

integrated farming system involving rice-fish-horticulture. Besides these systems, the pond

based organic farming of Penaeus monodon was developed by CIBA with inputs like

biocompost/ vermicompost, yeast based organic preparations, and low fish meal feed.

Effective utilization and exploration of natural productivity through organic manuring,

zero tolerance to artificial fertilizer, pesticides, chemotherapeutants, medicines including

antibiotics and integration of mangroves and other plants in the organic ponds were among

some of the salient features of this farming practice. The technology package developed is

based on improving extensive low input production system following organic principles

with developed organic inputs in terms of fertilization (biocompost/vermicompost), yeast

based organic preparations, seeding and feed for supply of nutrients (low fish meal feed)

and management of diseases (zero tolerance to antibiotics and chemotherapeutics).

Application of yeast based organic preparations and vermicompost prepared from

different substrates with inocula of vermin Eisoenia foetida, which were developed and

standardized through yard trials could ensure higher (275–350 mgC/m3/h) natural

productivity in organic ponds compared to that in conventional ponds (200–240

mgC/m3/h). Low fish meal based organic feed prepared from different plant protein

sources were tested in different combinations to arrive at a low cost feed with 15% fish

meal (protein contribution from different sources- fish meal: other marine protein sources:

plant protein sources- is 38:35:27 in control feed and 23:24:53 in low fish meal feed).

9.7.1. Production performance

The overall growth performance was better in organically managed ponds with a

productivity in the range of 1200–1400 kg/ha. The success of this farming technology is

marked with improvement in production level (14–21%), size at harvest (10–19%) with

better FCR (lowered by 4–18%) in the organic ponds.


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9.7.2. Economics of organic farming

Studies have shown that the common organic agricultural combination of lower input

costs and favourable price premiums can offset reduced yields and make organic farms

equally or often more profitable than conventional farms. Our study indicated that there is

a reduction in cost of production and increased gross and net returns in following organic

shrimp farming compared to conventional shrimp farming in our farm. This is also true for

other agricultural produce when it is done over the years. While standardising organic

shrimp culture we had observed that major profitability comes from the reduced FCR

compared to the conventional farms.

The pilot phase of organic projects in India could show that organic aquaculture

can be implemented with success and enabling direct market access to international

premium seafood markets. The long term success of these projects however will rely

mainly on: high product quality, local feed availability, constant supply with relevant

volumes from reliable suppliers, low production costs/ competitive price on the

international market, education and training of the farmers on organic principles.

9.8. Organic farming and sunderban

Sunderban, the world‟s largest delta with an area of 426,3000 ha and mangrove swamp,

the largest mangrove reserves in the world is also home to around 172 species of fishes, 20

species of shrimps and 44 species of crabs including two edible crabs (Jhingran, 1977).

The organic way of farming can help reverse the depleting bio-diversity in this region.

Since a shrimp farm‟s ecological footprint will depend on the intensity of farming, it has

been estimated to be as high as 35–190 times the size of the farm surface for a semi-

intensive system (Larsson et al., 1994; Kautsky et al., 1998), a low stocking organic

system will have very less impact on the ecosystem. Mangroves removed for allowable

purposes shall be replaced by replanting an area three times as large. Initial crop at CIBA

had the ponds planted with mangrove trees like Rhizophora mucronata, Avicennia alba

found locally just at the water line of the ponds. The selection was based on the salinity

tolerance and other adaptation of the mangrove plants. The dykes of the organic shrimp

pond can have vertical production zones. The lower part has different mangrove species,

grasses, and aquatic plants, and the upper part has the leguminous trees, vegetables and

fruit and flower trees. In some cases depending on the culture practice, mangroves and a

wide variety of aquatic plants which grow freely inside the ponds can be grown thus,


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creating a diverse wetland environment. The protection of the mangrove area (adjacent to

the shrimp farm) is possible by adapting organic farming integrating the mangroves and

ensuring that it was saved by the same industry that once threatened it. It is possible that

some of the abandoned shrimp farms will revert to mangrove forest in other parts of the

country.

9.9. Challenges for organic aquaculture

The challenges lies before organic aquaculture in India are sourcing organically certified

feeds or feed ingredients and producing organic broodstock and larvae. In case of penaeid

shrimps closed reproduction and antibiotic free hatchery and grow-out practices need to be

achieved within a specified time as per certain standards. Marketing tie up with production

which can help get the organic premium price needs to be channelized as much as the

certification process. The challenges also include the domestication of new species,

securing welfare of the cultured species, energy use, transportation, post-harvest needs, the

tropical and temperate growth pattern and other limitation. The greatest constraints faced

by transitioning farmers are the lack of knowledge, information sources, and technical

support through appropriate research and extension.

9.10. Conclusion

Organic aquaculture uses traditional and indigenous farming knowledge, while

introducing selected modern technologies to manage and enhance diversity, to incorporate

biological principles and resources into farming systems, and to ecologically intensify

aquacultural production. It gives scope to the farmers to be innovative. The greatest

constraints faced by transitioning farmers are the lack of knowledge, information sources,

and technical support. Greater government investment in appropriate research and

extension services can help overcome these constraints. As India has vast resources of

traditional/extensive farms which are close to nature, attributing these as sustainable

organic shrimp farming with little modification wherever necessary will be more defining

in its environmental, economic, health and animal welfare goals. Also our strength lies in

the network of extensive cluster farming. Image building of India‟s organic aquaproducts

will help creating a positive market to maintain its premium quality.


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Further readings

IFOAM, 2006. The principles of organic agriculture Available online at

http://www.ifoam.org/about_ifoam/principles/index.html Accessed 1 September 2006.

Jhingran, V.G., 1977. Fish and Fisheries of India. Hindustan Publ., Delhi Ch. Xv

pp954.

Kautsky, N., C. Folke., R. Ronnback and M. Troell., 1998. The Ecological Footprint: a

tool for assessing resource use and development limitations in aquaculture. Echos of

Expo 98 Bulletin 11(2), 5–6.

Larsson, J., C. Folke and N. Kautsky, 1994. Ecological Limitations and Appropriation

of Ecosystem Support by Shrimp Farming in Colombia. Environmental Management

18(5), 663–676.

Akshaya Panigrahi, J. Syama Dayal, Shyne Anand, T.K. Ghoshal, K. Ambasankar, R.

Anand Raja, G. Biswas, R. Saraswati, A.G. Ponniah, P. Ravichandran and S.A. Ali,

2010. Low input Low Cost Shrimp Farming System Based on Organic Principles.

CIBA Technology series (3) page no: (1-10).

FAO/NACA, 2007. Aquaculture certification: a programme for implementing the

recommendation of the committee on Fisheries Sub-Committee on Aquaculture.

FAO/NACA, Network of Aquaculture Centres in Asia-Pacific (NACA), Bangkok,

Thailand. 18 pp. Available

atwww.enaca.org/modules/wfdownloads/singlefile.php?cid=84&lid=787.

Wessells, C.R, Cochrane, K., Deere, C., Wallis, P. and Willman, R., 2001. Product

certification and eco-labelling for fisheries sustainability. FAO Fisheries Technical

Paper No. 422, FAO Rome, 83 pp.


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Fig. Organic farming demonstration at KRC centre of ICAR-CIBA and farmers pond in

Kerala.


114

Brackishwater Ornamental Fish Culture

Krishna Sukumaran, S.N. Sethi, Gouranga Biswas* and

Prem Kumar*



10.1. Introduction

Aquatic ornamental trade is today a multi-billion dollar industry with an estimated value

of 15 billion US dollars in which 1500–1600 species are traded globally (Moorhead and

Zeng, 2010; Oliver, 2001). The bulk of the ornamental fish traded constitutes freshwater

fish almost 90%, however, in term of value their marine counterparts contribute

significantly higher. A notable difference is that the freshwater species are mostly captive

bred (approximately 90%) and the marine species are collected from wild (approximately

90–95%) (Oliver, 2001). USA, Europe and Japan are the largest international markets for

ornamental fish, however, Asia is home to more than 65% of the exports (Ghosh et al.,

2003). Singapore has been a consistent leader in ornamental fish exports, followed by

Indonesia, Malaysia and China. In India, Kolkata has emerged as the major hub for

ornamental trade accounting to almost 90% of the exports followed by Mumbai and

Chennai. Ornamental fish species being traded in India are of two categories; the exotic

ornamental and native fish of India. The former with almost 288 varieties dominates the

domestic market. One hundred and eighty seven species are traded from India. The wild

catches form the bulk of the exports (85%) as compared to the cultured ones (Rani et al.,

2013). The ornamental fish market has been showing steady improvement in India with

the export values touching USD 3.8 million, a growth rate of 14.4% has been recorded in

the ornamental fish export. India‟s favourite export destination is Singapore (42.85%),

followed by Japan (13.88%) and Malaysia (9.97%). Freshwater fish dominate the scenario

of cultured ornamental fish species; molly, guppy, platy, swordtail, barbs, cichlids, angels,

Siamese fighter, tetras, gold fish, manila carps and sharks (Ghosh et al., 2010). The

existing scenario of export market based on wild collection is not a healthy one. Efforts in

developing and propagating seed production of untapped indigenous species will go a long

way for developing a robust ornamental fish industry in India. In this regards, CIBA has

10


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placed a major thrust on developing seed production technologies of many commercially

important species. Along with developing ornamental fish culture as large scale

production models, CIBA places a major emphasis on developing ornamental fish as a

livelihood option.

Presently the important candidate species on which CIBA places a major thrust are

spotted scat Scatophagus argus, moon fish Monodactylus argenteus, green chromide

Etroplus suratensis, orange chromide Etroplus maculates and crescent perch Terapon

jarbua. A wide diversity of brackishwater finfish species remain to be explored for their

ornamental value; figure of 8 puffer, Tetraodon biocellatus, ocellated puffer Takifugu

ocellatus, banded archer fish Toxotes jaculatrix, yellow catfish Horabagrus brachysoma

however there also lies great opportunity to do so in a sustainable manner by investing in

research for development of captive seed production technology for these brackishwater

species.

10.2. Spotted scat, Butter fish Scatophagus argus L. 1766

Taxonomy

Class- Actinopterygii

Order- Perciformes

Family- Scatophagidae

Genus- Scatophagus

Species- S. argus

The species is distributed in the Indo-Pacific, Kuwait to Fiji to southern Japan and Tahiti.

It inhabits coastal muddy areas, lower courses of freshwater streams and mangrove areas.

The fish is an omnivore feeding on detritus, filamentous algae, phytoplankton,

macrophytes and zooplankton. It attains a maximum total length of 380 mm. Females of

the species are reported to mature at 7–8 months at 150 g size while males mature at

relatively smaller size (Barry and Fast, 1992). Care has to be taken during handling of the

species due to its venomous spines on the dorsal, anal and pelvic fins which can cause pain

for long hours.

http://indiabiodiversity.org/species/show/238227

http://indiabiodiversity.org/species/show/238227


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CIBA has successfully developed protocols for captive maturation and induced

breeding of spotted scat (Kailasam and Thirunavukkarasu, 2011). Broodfish (up to 250–

300 g) size were raised in ponds and tanks by providing optimal environment and feed for

accelerating maturation. Successful spawning of the captive broodstock was achieved by

hormonal manipulations. A female fish weighing 200 g with ova diameter of 426 μ was

selected and administered with human chorionic gonadotropin (HCG) hormone as a prime

dose, followed by luteinizing hormone and releasing hormone (LHRHa), as a resolving

dose. Male fish were also administered the same hormones. Forty-eight hours after the

treatment, fish responded and ovulation was observed. Ovulated eggs and milt were

stripped from fishes and fertilization was facilitated externally. Larvae hatched out after 19

h of fertilization, and average size of the larva was 1.62 mm. Larvae were fed with rotifers

from day 3, up to day 10, and afterwards with brine shrimp, Artemia nauplii up to day 25,

till they reached 7–9 mm size. Fry were weaned to formulated feed and reared further. The

hatchery produced juveniles were supplied to entrepreneurs for further propagation. The

fish fetches a domestic market price of Rs.30–40 per piece (2 inch size).

10.3. Moon fish Monodactylus argenteus

Taxonomy


Order- Perciformes

Family- Monodactlylidae

Genus- Monodactylus

Species- M. argenteus

The species is distributed in the Indo-Pacific region. It inhabits bays, mangrove estuaries,

and tidal creeks. The fish feeds on plankton and detritus. It attains a maximum total length

of 270 mm. Male and female fish with TL 13 cm, 50–55 g size were observed to be in

mature stage (Prem Kumar et al., 2014).

At CIBA, broodstock of the fish is being maintained in ponds on commercial feeds

and captive maturation has been attained in the fish. Further trails are in progress for

captive breeding of the species (CIBA ANNUAL REPORT, 2013-14). Moon fish fetches

over Rs.100 per unit in the domestic market.


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10.4. Green chromide Etroplus suratensis

Taxonomy


Order- Perciformes

Family- Cichlidae

Genus- Etroplus

Species- E. suratensis

The species is naturally distributed in the southern peninsula and Sri Lanka. It inhabits

freshwater and estuarine water bodies. The fish is an omnivore feeding on detritus, aquatic

macrophytes and filamentous algae. It attains a maximum total length of 400 mm. Length

at first maturity has been reported as 195 mm in males and 200 mm in females (Bindu et

al., 2014). Fecundity of pearlspot varies from 500 to 7550 (Vijayaraghavan et al., 1981;

Bindu, 2006). CIBA has developed seed production of pearlspot in different systems;

ponds, tanks and cages.

10.4.1. Pond based system

Ponds with 100 m2 area, 1.2 m depth and 15–30 ppt water salinity, were stocked with 50

brooders after systematic pond preparation. Additional spawning surfaces were introduced

in the pond for egg attachment. Feeding was done using formulated feed. On observing the

presence of hatchlings, manuring was done with cow dung @ 500 kg/ha for enhancing

plankton production, artificial feed (25–30 g) was also provided. A production of 3500 fry

was observed in a year from 5 sets of breeding (Abraham and Sultana, 1995).

10.4.2. RCC tank system (20 ton)

In RCC tanks, continuous water flow through was provided. Half of the tank bottom was

provided with a soil base (4 inch), for egg attachment earthen tiles and hide outs were

provided. The tanks were stocked with mature pearlspot brooders at a density of 20 fish

per tank at a male female ratio of 2:3. Pair formation and breeding occurred naturally. Fry

were collected at regular monthly intervals by lowering the water level. A production of

1200–3500 seed per batch was obtained regularly and supplied to farmers and self-help

groups.


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10.4.3. Recirculatory aquaculture system (RAS) based tank system (1 ton)

Breeding trials of pearlspot were conducted in one ton rectangular plastic tanks provided

with a continuous water flow using a bio-filter facility. Each tank was provided with a

small plastic tub filled with clay soil to facilitate breeding. The breeding tank was stocked

with 3-4 mature brooders. After breeding the eggs were attached to the sides of the plastic

container and the brood fish were observed to take turns in defending the eggs. Larvae

were separated and reared using alternate live feeds, rotifer Brachionus plicatilis, Artemia

nauplii and by co-feeding with commercial larval diets. One of the most promising results

obtained was the production a total of 8000 larvae by a single pair stocked in six breedings

at an average breeding interval of 17.6±1.12 days and an average larval number per

spawning of 1333±143.

10.4.4. Seed production of pearlspot in hapas

Seed production of pearlspot was conducted in hapas set in ponds having gentle water

flow and salinity 25–30 ppt. Brooders were maintained in small cages on commercial fish

feed. Hapas (1×0.75×1 m) were fixed by casurina poles and clay soil was provided in

small plastic tubs suspended at 0.5 m depth. Just above the soil surface 1–2 ceramic tiles

were suspended to facilitate egg attachment. Each cage was stocked with 3–4 brooders.

Efforts at pair formation were usually observed a few hours after release of fish within

cages. In the initial trials hatchlings were collected from pit nets in cage and subsequent

larval rearing was practiced, following this method a seed production of 1000–1500 seeds

per cage could be observed. However, it was not always possible to observe larvae due to

turbidity in the pond. In majority of seed production trials, seed were reared within hapa

with parental care. A production between 200–300 numbers of seed (TL 28.11±1.49 mm;

Wt. 0.66±0.04 g) was observed per cage within 2-2.5 months.

10.5. Orange chromide Etroplus maculatus

Taxonomy


Order- Perciformes

Family- Cichlidae

Genus- Etroplus

Species- E. maculatus


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The species is naturally distributed in India and Sri Lanka. It inhabits lagoons and other

estuarine water bodies. The fish is an omnivore feeding on zooplankton and filamentous

algae. It attains a maximum total length of 80 mm. Fecundity of the fish is 1378

(Jayaprakash et al., 1979) approximately and reported to be between 140–231 eggs per

spawning (Bindu and Padmakumar, 2012). In nature, the fish form a breeding pairs and

attach eggs on the substrate. The species exhibits parental care and the offspring are taken

care of by the parents.

10.6. Crescent perch Terapon jarbua

Taxonomy


Order- Perciformes

Family- Teraponidae

Genus- Terapon

Species- T. jarbua

This species is naturally distributed in the Indo-Pacific region. It is a demersal species

occupying fresh, brackish to marine environments. The fish is an omnivore feeding on

insects, fish and invertebrates. It attains a maximum total length of 360 mm. The fish

exhibits occasional nipping behaviour. The species exhibits parental care and the eggs are

observed to be guarded by the male parent. CIBA has successfully initiated induced

breeding trials with hormonal manipulation using hCG and LHRH (CIBA Annual Report,

2014-15).

Further readings

Barry, T.P. and Fast, A.W., 1992. Biology of the spotted scat (Scatophagus argus) in

the Philippines. Asian Fish. Sci., 5: 163-179.

Bindu L. and Padmakumar., K.G., 2008. Food of the pearlspot Etroplus suratensis

(Bloch) in the Vembanad Lake J. Mar. Biol. Ass. India, 50 (2): 156 - 160


120

Bindu L. and Padmakumar., K.G., 2014. Reproductive biology of Etroplus suratensis

(Bloch) from Vembanad wetland system of Kerala. IJMS; 43, 4: 646-654.

CIBA Annual Report, 2010-11. Central Institute of Brackishwater Aquaculture,

Chennai. pp: 21-22.


Chennai. p: 38.


Chennai. pp: 76- 77.

Kailasam, M., Thirunavukkarasu, A.R., 2011. Mass-scale propagation of spotted

scat. ICAR NEWS 17, 3, p: 4.

Prem Kumar, A.R. Thirunavukkarasu, M. Kailasam, J.K. Sundaray , G. Biswas , R.

Subburaj, G. Thiagarajan and S. Elangeswaran, 2014. Captive maturation of the

silver moony fish Monodactylus argenteus (Linnaeus, 1758) under laboratory

conditions. Indian J. Fish., 61(1): 113-117.

Sultana, M.; Krishnamurthy, K.N. and Pillai, S.N., 1995. Biology, fishery, culture and

seed production of the pearlspot Etroplus suratensis (Bloch). CIBA Bulletin No. 7.

Central Institute of Brackish Water Aquaculture, Madras. 43 pp.


121

Biosecurity and Best Management Practices in

Shrimp Aquaculture

C.P. Balasubramanian, P.S. Shyne Anand and Akshaya Panigrahi


11.1. Introduction

Aquaculture has evolved from a simple but an elegant system, which has deep community

and family roots. In 1980s, there was a drive towards the export oriented agriculture crops.

Thus, much traditional agriculture has grown from basic food producing system to a

market driven complex export oriented enterprise. Shrimp culture in the tropics is the

paradigmatic example for this transformation. Tropical shrimp farming is considered to be

one of the few success stories of modern aquaculture. Evolution of shrimp aquaculture

from a fishery based pond production system of 1970s to a mature industry of 1990s is

spectacular. Its early success attracted many farmers, and this industry has become the

focal point of export in many tropical developing countries. However, the early success

and image of risk-free clean-industry has not lasted for many years due to the frequent

disease hits and crop failures. Success of shrimp culture often depends on how

successfully disease out-break can be prevented and controlled. Further environmental

protection, conservation of biosecurity and social equity are equally important for the

long-term sustainability of shrimp farming, although these elements are masked by the

short term gains and success.

It is extremely difficult to differentiate sub-optimal performance and disease in

aquaculture system due to the complexity of this ecosystem. Disease is the end result of

series of linked events involving environmental factors, health status of cultured stocks,

presence of an infectious agent and poor husbandry. In order to prevent the disease out-

break and negative environmental effect of aquaculture, the whole aquatic ecosystem

including ecological process must be taken into consideration. The traditional pathogen-

focused approach, therefore, should be replaced by more holistic approach focusing the

whole ecosystem. The best management practices (BMPs) and the strict biosecurity

measures are the essential tool to manage the disease and environmental health.

11


122

History of BMPs can be traced back to the history of aquaculture or the history of

any production system. It is evolved from the producers‟ quest to reduce the input and

costs, and vast majority of the BMPs are generated by the producers. No single BMP

reduces key impact equally, as there is no one-size fit for all. The most effective BMP

depends on species cultured, type and magnitude of impact, scale of production, resource

available to producers and overall management of the system. As BMPs in aquaculture

and biosecurity protocols are intimately linked, in this lecture note, these aspects are

treated together.

11.2. Biosecurity

The entire stakeholders of aquaculture concerned about biosecurity: Consumers need to

ensure the seafood that they eat are safe, the processors have to follow HACCP guidelines

to provide safe seafood, investors should protect their investment from the preventable

losses. The Biosecurity workshop for aquaculture defined biosecurity as: “an essential

group of tools for the prevention, control, and eradication of infectious disease and the

preservation of human, animal, and environmental health”. The principles of biosecurity

are not only to keep away the pathogen from the farming environment but also from the

country.

The success of poultry industry world-wide is the successful implementation of

biosecurity. The use of similar protocol has been prompted in shrimp farming. In Poultry,

biosecurity is defined as: “cumulative steps taken to keep disease from a farm and to

prevent the transmission of disease within an infected farm to neighbouring farms”. It is a

team effort, shared responsibility and an ever-time process. Basic philosophy behind

biosecurity is to prevent the entry of pathogen, ensure the best living condition to the

animals and to provide a clean product to the customer. The principles of biosecurity in

the poultry can be applied to aquaculture.

In the following section, BMP and biosecurity measures to be taken at each stage

or each component of farming has been dealt.

11.2.1. Site selection

Poorly located sites are often found to be failed and provide negative ecological impacts.

Potential problems should be identified and measures should be taken to avoid maximum

problems. Mangrove sites and other coastal wetlands should be avoided, as these habitats

are inherently important for ecological well-being.


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11.2.2. Farm design

Modular seawater system with reservoir ponds before use in culture is found to be

effective. All these farm design directly depends on the characteristic site and level of

intensity.

All inlet and outlet systems should be free from leakage, and to avoid carriers such

as crabs and birds, preventing nets should be installed. Additionally, the management

measures to improve soil quality and other preventive measures should be taken as per the

following Table.

Strategies Benefits

Sludge removal and disposal away from the pond

sites

Increase the carrying capacity of the

pond, and improve the pond general

conditions.

Adoption of minimal water exchange Increase the stability of culture

environment; minimize the entry of

influent pathogens.

Water filtration using twin bag filters of 300 µm

filters

Prevent the entry of disease carrying

vectors.

Water treatment using approved chemicals such as

chlorine, and aging the water

Eradication of pathogens.

Maintaining the water depth at least 80 cm at

shallow part of depth

Prevent the formation of benthic algae

11.2.3. Broodstock and post larvae

During the early days of shrimp farming, farmers used wild seed stock entering along with

the tidal inflow or captured wild broodstock. This practice was replaced later with the use

of hatchery produced seeds obtained from the wild caught broodstock. This wild caught

broodstock are often carriers of pathogens. Thus, it is understood that dependence of wild

broodstock is important source of pathogen entry and without delinking the wild fishery

and aquaculture, the disease management cannot be attained effectively. Thus, use of

captive reared and specific pathogen free (SPF) broodstock are found to be crucial. The

process of development of SPF broodstock is given below.


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11.2.3.1. Development of SPF stock

Whatever the methods have been incorporated to eradicate the occurrence and out-break

of disease in aquaculture ponds, none could provide enough protection, if we use seed

stocks derived from the wild brooders. Therefore, the most important principle of

biosecurity is the use of domesticated stocks, which have been cultured under controlled

conditions and that have been under active disease surveillance programme. The

development and use of SPF stock is, perhaps, the best management strategy for stock

control in farms or regions or countries. Although in market place, these stocks are called

as “disease free”; in reality they are free of specific disease causing agents. It should be

understood that no living being is completely free of diseases. SPF means the stock of

interest has at least 2 years of documented historical freedom of pathogens listed on the

working list. These pathogens should have the following criteria: 1) the pathogens must be

excludable, 2) adequate diagnostic methods should available and 3) pathogen should pose

significant threat to industry.

The process of SPF development begins with identification of wild or cultured

shrimp stocks. The samples of this stock then will be tested for specific pathogens using

appropriate diagnostic procedures. If these stocks are free from specific pathogens, they

are designated as founder population or F0, and they will be reared in a primary quarantine

facility. During the primary quarantine F0 stock will be monitored periodically for the

specific pathogens. If this stock is detected for any of the specific pathogens, the stock will

be destroyed. The stock will be moved to secondary quarantine, if they are free of specific

pathogens. At this facility this stock will be matured, selected and produce F1 generation.

These F1 stocks will be maintained in quarantine further to ensure that they are free from

specific pathogens. These SPF stocks will be supplied to hatcheries and breeding centres.

11.2.4. Use of stress test

Exposure to weak concentration of formalin or with change in salinity can be used to

determine whether post larvae are strong enough to survive stocking into ponds.

11.2.5. Feeds and feed management

Manufactured feeds account for 60-70% of total operating cost in shrimp aquaculture.

Feeds are one of the important concerns for environmental group because it depends on

marine capture fishery for fish meal and fish oil. Further, 20 to 40% of feed remained


125

unused by shrimp becomes pollutant to the pond. Use of high quality feed, and feed should

not contain more nitrogen and phosphorus than shrimp needed. Feed management

practices should be carefully monitored. It should be assured that shrimp consume as

much as feed they can consume to avoid the wastage of feed. Check tray should be used to

avoid over feeding and under feeding. Feeding should be practiced four to five times per

day, and it should be broadcasted widespread. Feed should be adjusted with biomass and

appetite of shrimp. Natural productivity has an important role in the nutrition of farmed

shrimp. The larvae at early stages cannot consume the pelleted feed as efficiently as larger

shrimps, and therefore, natural biota of the culture pond plays an important role in the

nutrition during the early phase of culture. Therefore, production and maintenance of

natural productivity has important role in the sustainable shrimp farming. Do not use fresh

feed or other material for feeding the farmed shrimp.

11.2.6. Health management

Regular monitoring of shrimp for health status should be carried out; sick and moribund

shrimps should be removed regularly. In the case of disease outbreak, strict quarantine

protocol should be followed to prevent the spread of disease. As many stressors reduce the

innate immunity of many cultured shrimps, measures should be taken to minimize the

stress such as maintenance of high oxygen content in the water, maintaining stable pH,

temperature and salinity of rearing water, minimize the use of feed, water exchange etc.

Eradication of disease at the beginning is easier and do not use antibiotic. Use probiotics

judiciously and only when the efficacy of the product is proved.

11.3. Conclusion

BMPs and their implementation are most crucial component for successful shrimp

aquaculture. The most important step of the biosecurity is exclusion of pathogen from the

system. Education on biosecurity makes farmers more aware. It provides set of tools to

protect the crop, and eventually it makes shrimp farming more profitable and sustainable.


126

Application of Periphyton and Biofloc Technologies-

New Opportunities in Brackishwater Farming

P.S. Shyne Anand, C.P. Balasubramanian and Akashaya Panigrahi


12.1. Introduction

Over the years, the rapid growth of aquaculture all over the globe has brought in

intensification of the aquaculture practices, especially shrimp culture. In most countries

including India, many large-scale extensive systems have converted to semi intensive or

intensive systems with application of modern technologies. However, the intensification

was not commensurate with factors like availability and use of quality seed or other inputs

which could drive for a successful production. In the course of adopting high resolution

culture methods, brackishwater aquaculture like shrimp farming began to face issues of

increasing price of commercial feed, disease outbreaks, environmental degradation etc.

Alternatively, exploration of ecofriendly culture methods suitable for sustainable shrimp

production in India had been at the anvil. Amongst, sustainable ecofriendly farming

methods like biofloc and periphyton based farming systems are getting momentum across

the world.

If we look in to aquatic ecosystems, it depends on the exploitation of autotrophic

and heterotrophic microbial food webs. Both the food webs consistently appear as a major

contributor in total production of target aquatic animals as these are consumed directly by

the cultured animals or by other small animals on which the cultured species feed.

However, filter-feeding limiting to phytoplankton could not fulfill the full energy demands

for the aquatic organism. This emphasizes the importance of other larger size food

particles in natural systems such as surface concentrated scums of blue green algae,

periphytic algae, heterotrophic microbial floc etc. which can be easily harvested by

cultured organisms. This shows a tremendous scope of periphyton and biofloc based

systems in ecofriendly sustainable way.

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12.2. Substrate based aquaculture

Use of submerged substrate in natural environment to aggregate fish is an age-old practice

in different parts of Africa and Asian countries. Acdja-based fisheries prevalent in West

Africa, where dense tree branches are placed in lagoons to attract fishes are pioneering

examples for substrate based farming system. “Katha Fisheries” in Bangladesh and

“Samarahs” or brush parks in Cambodia prevalent for centuries employ the same

principle.

In substrate based aquaculture, submerged substrates in culture ponds provide sites

for the development of periphyton, a complex mixture of autotrophic and heterotrophic

micro-organisms which serve as an excellent natural food for different species of fishes or

shrimps. Apart from this, it provides shelter for cultured organisms and improves water

quality through nitrification.

12.3. What is periphyton?

Periphyton refers to the entire complex of attached aquatic biota on submerged substrates

forming an excellent quality natural food for the cultured fishes

and shrimp. It comprises phytoplankton, zooplankton, benthic

organisms and detritus. Aquatic animals are mechanically more

efficient to graze two-dimensional layer of periphyton than

depending on filter algae from a three-dimensional planktonic

environment. So, adoption of substrate based shrimp culture

enhances the nutrient-transfer efficiency of the system due to

shift from less stable phytoplankton to more stable periphyton

community. Apart from providing natural food, periphytic algae

grown on the substrate act as biofilter, enhance nitrification process and help to reduce

total ammonia nitrogen (TAN) and nitrate-N, phosphate-P in water column.

12.3.1. Influencing factors in periphyton production

Development of periphyton on submerged substrate is influenced by range of factors, such

as availability of dissolved nutrients (nitrate and phosphate) in the water column, presence

of light, water depth, and nature and type of substrate. The periphyton growth and

composition dynamics regulate the grazing efficiency and food and feeding habit of the

cultured species. However, the quality and quantity of periphyton colonizing depends on

the nature and type of substratum. Bamboo, wood, paddy straw, sugarcane bagasse are


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widely used natural substrates for growth of periphyton. These substrates installed in

shrimp ponds generate an additional surface area of 10–15 %. Artificial substrates for

periphyton development like discarded plastic irrigation pipes, empty plastic bottles or old

nylon webbing, ceramic tile and fibrous scrubber are inefficient. Natural biodegradable

substrates are found to be more efficient than synthetic substrates because of the nutrient

leaching occurring at the substrate-water interface in natural substrates. Amongst various

natural substrates, bamboo is one of the most widely used ones because of its availability,

durability, easy to use and efficient for high-quality periphyton growth.

Development of periphytic algae and its distribution is dependent upon the nutrient

level in the water column. Application of organic and inorganic fertilizers stimulates the

growth of periphytic algae. The recommended levels are: organic fertilizer @ 500–1000

kg/ha and inorganic fertilizers like urea and single super phosphate (SSP) @ 25–100

kg/ha. Fertilized ponds develop a considerable amount of periphyton over a period of 2-4

weeks. About 10% of the original dose of inorganic fertilizers, i.e. urea and SSP at 10–20

kg/ha is applied periodically (monthly) if sufficient primary productivity of pond is not

maintained. Lower and higher doses of fertilization result in competition between algal

species dominance for substrate, nutrients and light, as well as shading by plankton, which

impedes the sunlight penetration into the water column resulting in hampering the

periphyton growth. So, optimal to moderate nutrients levels provide the most favourable

conditions for development of diverse algal species over submerged substrate. The

periphytic algae must be grazed constantly and kept in an exponential growth in order to

stimulate periphyton production and maintain high productivity. Increased standing

biomass in the absence of grazers may lead to self-shading and death of algae, with

consequent sloughing and dislodgement of the community.

12.3.2. Nutritional composition of periphyton

Periphyton generally composed of more than 30 genera of periphytic algal community

belonging to groups like diatoms, green algae, blue green algae along with zooplankton

communities like ciliates, flagellates and copepods. These microalgae and zooplankton

enrich the quality of periphyton and are rich source of essential nutrients like

polyunsaturated fatty acid (PUFA), amino acids, vitamins and pigments. Proximate

analysis of periphyton broadly meets the dietary needs of fish/ shrimp in aquaculture.

Periphyton developed over bamboo substrate has a composition of 12–30% protein, 2.1–


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9% lipid, 28% ash and a rich source of EPA (3–15 % of total fatty acids), DHA (2–3% of

total fatty acids), essential amino acids with gross energy of 19–20 kJ/g..

12.4. Role of periphyton in aquaculture

12.4.1. Effect on water quality

Periphyton developed over submerged substrate plays an important role in improving the

water quality in culture ponds. Periphytic algae grown on the substrate act as biofilters in

enhancing the nitrification process and help to reduce total ammonia nitrogen (TAN) and

nitrate-N and phosphate-P in water column. Submerged substrates also decrease water

turbidity and occurrence of algal bloom in water column, and increase abundance of

benthic macro invertebrates through biological or ecological process.

12.4.2. Periphyton in fish culture

Submerged substrates are widely being used in finfish culture like tilapia, Indian major

carps, Labeo calbasu, grey mullets, milk fish etc. Periphyton forms a preferable natural

food for herbivorous and omnivorous fish species. Studies conducted in Bangladesh show

that periphyton equivalent to the pond surface area (100%) supports a fish production of 5

ton/ha/year without need of a supplementary food.

12.4.3. Periphyton in shrimp culture

Microalgae are important dietary source during larval and post larval stages of penaeid and

non penaeid shrimps. Benefit of substrate in shrimp culture varies with the growth stages,

type of species and their feeding habits. Provision of substrate in the early growth stages

or nursery rearing stages of penaeid shrimp improves the survival even at high stocking

density as it serves as refuge for cultured shrimp. It is reported that 28% higher survival

was obtained in the nursery rearing of L. vannamei in tanks where fiberglass window

screens were provided. Being benthic animals,

shrimps are constrained to two-dimensional space

rather than three-dimensional space. Hence,

substrate provision could reduce the negative effect

by increasing the living space for the shrimp.

Studies have shown that significantly higher

shrimp production, lower feed conversion ratio

(FCR), better immune responses and water quality

in substrate based shrimp culture of P. monodon, L. vannamei and F. paulensisi. There are


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also various reports about the benefit of substrate based system in enhancing the yield and

survival of freshwater prawn, Macrobrachium rosenbergii. Low density shrimp farming is

advisable in substrate based system as periphyton community developed can also increases

the aeration demand during the night hours apart from shrimp dissolved oxygen

requirement.

12.5. Biofloc based aquaculture

In aquatic ecosystems, heterotrophic community mainly bacteria, protozoa, fungi and

associated detritus form a major contributor to the total production of cultured species.

Microbial protein is generated in aquaculture ponds when organic matter added as manure

or feed is decomposed by microorganisms under aerobic condition. Microbial breakdown

of organic matter leads to the production of new bacterial cell with the direct assimilation

of dissolved nitrogenous matters (Avnimelech, 1999).

Biofloc technology enhances water quality and produces single cell microbial

protein by increasing the C:N ratio in the aquaculture system, through the external carbon

source or elevated carbon level in the feed (Crab et al., 2012). If carbon and nitrogen are

well balanced, bacteria rapidly utilize ammonium ion. This process is more rapid and

powerful in immobilizing ammonium ion than conventional nitrification process. In

biofloc system, microbial community reaches a density in the order of 107

cfu/mL and

functions both as a bioreactor for controlling water quality and as protein source for

cultured aquatic organisms.

12.5.1. Factors influencing biofloc production

Carbon nitrogen ratio plays a pivotal role in immobilization of inorganic nitrogen into

bacterial cell. As bacterial cells have C:N ratio 5:1 and the conversion efficiency of

bacteria is 40–60%, C:N ratio of 10 or more in the feed is required for the growth of

heterotrophic microorganisms (Avnimelech, 1999). Heterotrophic bacteria assimilate

inorganic nitrogen (especially ammonia nitrogen) originated from feed, fish/ shrimp

excretions or inorganic nitrogenous fertilizers. Commonly used carbohydrate sources for

carbon supplementation are starch, wheat flour, wheat bran, molasses, acetate, glycerol

and glucose.

The microbial communities formed in the biofloc consist of phytoplankton,

bacteria and aggregates of living and dead particulate organic matter. Microbial flocs

generally composed of attached heterotrophic bacteria, filamentous cyanobacteria,


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dinoflagellates, ciliates, flagellates and rotifers apart from detritus and ash (Ballester et al.,

2010). These indicate that bioflocs are complex of diverse groups of autotrophic and

heterotrophic organisms.

12.5.2. Nutritional composition of biofloc

Nutritional value of biofloc depends on type of carbohydrate source used for its production

and its community structure. Bioflocs are rich in protein, vitamin and minerals. Based on

the various scientific reports, biofloc contain 28–55% crude protein, 4–7% crude lipid, 30–

40% ash and 25–35% nitrogen free extract on dry matter basis.

12.5.3. Role of biofloc in aquaculture

There are numerous reports about the enhanced growth, survival and health status of

shrimp reared in ponds rich in natural productivity than in clean water, even after supply

of nutritionally complete feed.

12.5.3.1. Biofloc in bioremediation

The biofloc system has many advantages for sustainable aquaculture as it minimizes water

exchange and maintains adequate water quality in the culture ponds. At higher C:N ratio,

immobilisation of inorganic nitrogen takes place by bacteria which decreases the toxic

NH3-N within a few hours as compared to slow conventional nitrification process.

12.5.3.2. Biofloc in shrimp aquaculture

Experimental production of shrimp based on the concept of biofloc technology (BFT) had

been started since early 1980s. Various reports are available with regards to uptake of

microbial flocs by different sizes of fish and shrimp. Now, biofloc based culture systems

have been widely applied in zero water exchange systems of several shrimp species such

as P. monodon, L. vannamei, F. paulensis and M. japonicus. About 10–20% potential feed

gain is estimated by application of biofloc technology which can reduce the production

costs considerably since feed represents 40–50% of the total production cost.

12.5.3.3. Biofloc as dietary ingredient

Even though bioflocs provide an excellent natural food in in situ based system; uptake of

the bioflocs by fish/shrimp depends on the species, growth stages, feeding habits of the

shrimp or fish and biofloc properties such as floc size, floc density etc. Nutritional

composition of biofloc confirms its nutritional suitability as dietary ingredient for shrimp

feed. Therefore, biofloc produced from external sources can be used as a dietary ingredient


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in shrimp feed. Studies revealed that incorporation of dried biofloc at 4–20% inclusion

level in shrimp died significantly improved growth rate in penaeid shrimps. Similarly, this

alternative ingredient offers the shrimp industry a viable option to replace costly fish meal

and traditional plant protein by cheaper biofloc produced from aquaculture effluent.

12.5.3.4. Biofloc in shrimp health

In addition to the advantages of biofloc technology in bioremediation and nutrition, recent

studies have shown biofloc as a possible alternative measure to fight pathogenic bacteria

in aquaculture. It is reported that microbial flocs contain many strains of probiotic bacteria

which improve immune responses and less disease occurrence compared to conventional

culture system.

12.6. Conclusion

Integration of substrate and C:N ratio manipulation help to maintain better water quality

by reducing toxic metabolites like TAN, NO2-N and improve the FCR, growth rate and

survival of shrimps and fishes. Substrate allows the growth of epiphytic algal community

that is served as natural feed. Further, the increase in C:N ratio converted toxic inorganic

nitrogen waste into single cell microbial protein which was observed as increased

heterotrophic bacterial load and lower inorganic nitrogen content in water. Thus,

periphyton and biofloc based farming systems enhance growth performance, FCR and

total productivity through optimum utilization of natural productivity in ecofriendly

manner.

Further readings

Anand, P. S. S., Sujeet Kumar, Panigrahi, A., Ghoshal, T. K., Syama Dayal, J.,

Biswas, G., Sundaray, J. K., De, D., Ananda Raja, R., Deo, A. D., Pillai, S. M. and

Ravichandran, P., 2013. Effects of C: N ratio and substrate integration on periphyton

biomass, microbial dynamics and growth of Penaeus monodon juveniles. Aquacult.

Int., 21:511–524.

Avnimelech Y., 1999. Carbon/nitrogen ratio as a control element in aquaculture

systems. Aquaculture 176: 227–235.


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Azim ME, Asaeda T, Verdegem MCJ, van Dam AA, Beveridge MCM, 2005.

Periphyton structure, diversity and colonization. Periphyton: ecology, exploitation and

management 15-33.

Crab, R., Chielens, B., Wille, M., Bossier, P., Verstraete, W., 2010. The effect of

different carbon sources on the nutritional value of bioflocs, a feed for Macrobrachium

rosenbergii postlarvae. Aquac. Res. 41: 559–567.

Ballester, E. L. C., Abreu, P. C., Cavalli, R. O., Emerenciano, M., de Abreu, L.,

Wasielesky, J. W., 2010. Effect of practical diets with different protein levels on the

performance of Farfantepenaeus paulensis juveniles nursed in a zero exchange

suspended microbial flocs intensive system. Aquacult. Nutr., 16: 163-172.


134

Brackishwater Fish and Crustacean Diseases and

Their Control

Sanjoy Das, S.K. Otta*, M. Makesh* and S.V. Alavandi*



13.1. Introduction

Brackishwater aquaculture is one of the fastest growing sectors of India with high growth

rate and export potential. Brackishwater shrimp culture is a highly profitable enterprise of

India and it earns a huge amount of foreign exchange every year. During 2013-14, India

earned Rs.30,213 crores through export of fish and fishery products, and the contribution

of frozen shrimp alone was 64% (Rs.19368 crore) (MPEDA, 2015). But occurrence of

different diseases at different point of time in brackishwater aquaculture systems of India

and other parts of world played havoc with crop failure leading to heavy economic losses.

In case of brackishwater finfishes, viral nervous necrosis and iridovirus infection are the

most important diseases, whereas white spot disease caused by white spot syndrome virus

(WSSV) is the most devastating disease of the shrimp industry. In a study conducted

during 2006-08, it was observed that the gross national losses in the country due to shrimp

diseases was 48717 metric tons of shrimp, valued Rs.1022 crore and employment of 2.15

million man-days (Kalaimani et al. 2013). Considering the facts that there are few options

for disease control in aquaculture, best management practices of BMPs and biosecurity

protocols play a major role in the management of aquatic animal diseases.

13.2. Diseases of brackishwater finfishes

13.2.1. Viral nervous necrosis (VNN)

Viral nervous necrosis (VNN) is a devastating disease of both marine and brackishwater

finfishes and it causes a very high mortality, especially in larval and juvenile stages. This

viral disease is caused by a piscine nodavirus, which belongs to the genus Betanodavirus

that possesses a single stranded positive sense RNA genome. This is a non-enveloped

virus with icosahedral symmetry, and of approximately 37 nm diameter and 3.5 kb

genome size. This disease is also known as Viral Encephalopathy and Retinopathy (VER).

13


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In India, the disease was first reported in Chennai in 2005 and later on, it was reported in

other parts of country. VNN affects different cultured and wild species of brackishwater

and marine fishes including Lates calcarifer (Bhetki/ barramundi), Mugil cephalus,

Chanos chanos (milkfish), Epinephelus tauvina, Sardinella longiceps, Amblygaster

clupeoides, Mystus gulio, Leiognathus splendens etc. The disease also affects freshwater

fish like Nile tilapia (Oreochromis niloticus) and the ornamental fish guppy (Poecilia

reticulata). This disease is generally transmitted through influent contaminated water,

introduction of infected juvenile fish, implements and translocation of fish from one

location to another etc. Very often different wild fishes with asymptomatic and sub-

clinical infection act as carriers of this virus. The vertical transmission from infected

spawners to fry has also been reported.

The affected fishes show anorexia (loss of appetite), spiral swimming and dark

colouration of the body. VNN causes cellular necrosis and vacuolation in the central

nervous system including brain and spinal cord and retina. In juveniles, the mortality rate

is higher than the adult although the occurrence of the disease has been reported in all age

groups. The disease is highly fatal and mortality rate is sometimes as high as cent percent,

in larval and juvenile stages. The diagnosis of this disease is mainly based on finding of

characteristics lesion in CNS and retina by light microscopy and detection of the virion by

electron microscopy. Different serological tests like enzyme linked immonosorbent assay

(ELISA) can be used to detect the presence of viral antigens. The most sensitive and

reliable technique for the diagnosis of VNN is the detection of viral RNA by reverse

transcriptase-polymerase chain reaction (RT-PCR).

Generally, no treatment method or commercial vaccine is available for VNN.

Experimental oral vaccine has been developed against VNN. This is based on artemia

encapsulated recombinant Escherichia coli expressing VNN capsid protein gene. Viral

screening of broodstock should be done by RT-PCR to avoid infection to the larvae by

vertical transmission. Regular disinfection of the hatchery premises with chlorine (50

ppm) should be done. Fertilized eggs should be disinfected with different disinfectants like

ozone (1 mg/ L for 1 min). Separation of larvae/ juveniles from brooder will minimize the

risk of disease transmission. An experienced fish health professional may be contacted for

help.


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13.2.2. Diseases caused by Iridoviruses

Iridovirus infection affects Asian seabass (Bhetki or L. calcarifer) and farmed red sea

bream (Pagrus major) with very high mortality, especially in the juvenile stages. A double

stranded DNA virus with 130–300 nm size belonging to the genera Lymphocystivirus and

Ranavirus are considered as agents of this disease. These viruses are labile to heat and can

be easily inactivated by heating at 56ºC for 30 min. Viruses under genus Lymphocystivirus

causes localized infection, while systemic disease is caused by Ranavirus leading to heavy

economic losses. The transmission of Iridovirus is generally horizontal through

contaminated water. The incidence is usually more during summer season, when the water

temperature is more than 25ºC.

The affected fish becomes lethargic and anaemic. The petecheal haemorrhage is

seen in gills with enlargement of spleen. The mortality rate depends upon different factors

like age, water temperature, water quality and other culture conditions and it varies greatly

from 0 to almost 100%. Diagnosis is mainly based on immunological detection of

pathogen by IFAT (Indirect Fluorescent Antibody Test), and spleen and kidney tissue are

the most suitable organ for this pathogen detection. The sample should be stored at –80ºC

for longer storage. On histopathology of liver and spleen with Giemsa staining,

abnormally enlarged cells with very deep stain are observed. The viruses can be observed

directly in the infected tissues by electron microscopy. ELISA has also been developed for

detection of viral antigen. Different molecular methods like PCR and real time PCR can

also be employed for detection of this virus with high degree of specificity and sensitivity.

For control of Iridovirus infection, a good aquaculture practice is very helpful.

These include stocking of pathogen free fish, maintenance of good water quality,

avoidance of overcrowding and overfeeding etc. For red sea bream Iridovirus infection, a

formalin-killed vaccine is commercially available.

13.2.3. Diseases caused by Vibrio spp.

Different species of Vibrio including V. harvei, V. anguillarum, V. salmonicida, V.

parahaemolyticus, V. alginolyticus and V. vulnificus affect different species of

brackishwater fishes. The infection through different species of Vibrio is collectively

known as vibriosis. The incidence is more in summer season, when the water temperature

is high. Common symptoms of vibriosis include anorexia, lethargy, darkening of body,

and reddened ulceration of body haemorrhage at mandible, isthmus, bases and rays of fins.


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Splenomegaly (enlargement of spleen) is also observed in some cases. The gut is often

filled with pale, yellow and serous fluid. The reddened ulceration is due to haemorrhages

on body surfaces. Due to presence of haemorrhage on different parts of body, vibriosis in

Asian seabass is popularly known as „Ulcerative Haemorrhagic Septicaemia‟. The body is

very often covered with thick layer of mucus. The disease is more severe at nursery stages.

The diagnosis of the disease is generally done by isolation of particular Vibrio spp., slide

agglutination test using specific antisera. Brain and kidney of suspected fishes are the

suitable organs for diagnosis of vibriosis.

Vaccination of seabass against V. anguillarum serotype O1 is reported to be

effective. Aquavac Vibrio Oral®, which is meant for vaccination of trout against vibriosis,

has also been successfully used for prevention of vibriosis in Asian seabass.

13.2.4. Infection by Aeromonas spp.

Aeromonas are normal inhabitants of the aquaculture environment. When fish suffers from

environmental stress or injury, they act as opportunistic pathogens and cause

haemorrhagic disease with high mortality. The predisposing factors of Aeromonas

infections are high temperature, sudden fluctuation of pH, high CO2, depletion of

dissolved oxygen and high level of free ammonia in water etc. Aeromonas infections in

brackishwater fishes are mostly caused by A. hydrophila, A. caviae and A. punctata.

Haemorrhage is generally found in fin and tail of affected fishes and in severe cases,

erosion of tail and fin can also be observed. Shallow ulcers may develop at the

haemorrhagic sites. The congestion of haemorrhage may also be observed at the

haemorrhagic sites. Aeromonas spp. can be isolated from diseased fish by Starch-

ampicillin agar or Rimler-Shotts agar containing novobiocin.

13.2.5. Columnaris disease

This disease is caused by a Gram negative bacterium called Flexibacter columnaris.

Columnaris disease is important in different freshwater fishes. Asian seabass especially at

juvenile and nursery stages are susceptible. This disease is characterized by saddle-shaped

lesion in the mid-body position near dorsal fin and is mostly associated with over-

stocking, poor hygiene and skin trauma. Treatment can be done by dipping affected fish

with copper sulfate (2 mg/ L) for 1–2 min or by application of potassium permanganate at

the rate of 4–6 mg/ L to the affected pond.


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13.2.6. Septicemia and organ rots

Gill rot is very often observed in pearlspot (Etroplus suratensis) and is caused by a

bacteria named as Klebsiella pneumoniae. The affected fish show isolated movement,

anorexia, restlessness, orientation against current and gill tissue decay.

Tail rot disease in pearlspot (Etroplus suratensis) is characterized by loss of natural

colour, swimming near water surface etc. This disease is caused by Proteus vulgaris, a

Gram negative bacterium.

Haemorrhagic septicaemis in pearl spot is caused by Pseudomonas aeruginosa and

is characterized by reddening of body, swollen belly, septicemia, inflamed anus, spleen,

swim bladder and anaemia.

13.2.7. Epizootic Ulcerative Syndrome (EUS)

This disease, which is called as Red spot disease, is a very common disease of wide

varieties of freshwater fishes causing significant economic losses to the fish farmers.

Among brackishwater finfishes, the disease often affects Mystus gulio (Nuna tengra),

different species of mullets (Mugil spp., Liza spp.) and Asian seabass. Milkfish are

generally resistant to EUS. The disease is caused by an oomyceteous fungus,

Aphanomyces invadans. The genera Aphanomyces is a member of group of organisms

commonly known as water molds. Previously, this organism was considered as fungus

because of filamentous growth and mycelia like structure, but presently classified with

diatom and brown algae in a group called Stramenopiles or Chromista. The disease is very

often associated with secondary bacterial infections. The spread of diseases generally

takes place through water-borne transmission of zoospores, contact between fishes and

introduction of infected fish into non-infected ponds. Rate of mortality is generally more

during long colder seasons. Heavy rainfall is also considered as a predisposing factor of

this disease.

On the head of affected fishes, haemorrhagic ulcers are frequently observed and it

very often extends to skull leading to exposure of brain. Diagnosis of the disease is

generally done by observation of symptoms and lesions, and generally confirmed by

detection of non-septate, branchial hyphae in the periphery of the lesion. No particular

vaccine is commercially available for prophylaxis against this disease. The affected fish

should be destroyed with proper disinfection at farm premises. Before stocking for next

time, the pond should be adequately dried and limed.


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13.2.8. Diseases caused by Dinoflagelletes (e.g. Velvet disease in Asian seabass)

The dinoflagelletes are a large group of flagellate protists that constitute the Phylum

Dinoflagellata. They are generally marine planktons. Amyloodinium spp. is a common fish

dinoflagellete and it usually adheres to gill filaments or body surfaces of the affected fish.

High stocking density and high level of organic matter are predisposing factors of

infection with dinoflagelletes.

Amyloodinium ocellatum causes velvet disease in Asian seabass and this disease is

characterized by white spots on the skin and gills, tissue necrosis and abnormal swimming.

The affected fish usually come to the surfaces of water and very frequently near aerators.

Necrosis of gill and skin is observed with dark discolouration of the body. Very high

mortality may be observed if not treated in time. The affected fish can be dipped in 200

ppm of formalin for 1 h or in 0.5 ppm copper sulfate for 5 days.

13.2.9. Diseases caused by ciliates group of protozoa

The ciliates are a group of protozoa, which possesses cilia, the hair like organelles.

Ciliated protozoa are placed within the Class- Ciliata. The common ciliates, which affect

brackishwater fishes, are Cryptocaryon and Trichodina. Cryptocaryon is generally found

on gill and external surface of the fish. Over-crowding and low water temperature are

generally considered as predisposing factors for infection with Cryptocaryon. The

Cryptocaryon infection is generally characterized by numerous white spots on the body

surface and increased mucus production in the affected part. This disease is also known as

„white spot disease‟. Trichodina spp. is another important ciliated protozoa, which causes

trichodiniasis in Asian seabass. It generally attaches to skin and gills. The affected fishes

show heavy mucus production around the gills leading to respiratory distress by clogging

of gills. The disease can be controlled by formalin or acriflavin bath.

13.2.10. Flukes and crustacean infections in brackishwater finfishes

Benedinea spp. and Dactylogyurs spp. are the common skin flukes in fishes. They

generally affect body surface, eyes and occasionally gills. Due to the damage of tissues, it

becomes prone to secondary bacterial infection. The affected fishes become lethargic with

excessive mucus production, opaque eye and skin lesions.

The commonly affecting gill flukes of fishes are Gyrodactylus spp. and

Diplectanum spp. Poor water quality such as low pH and high nitrates and nitrite levels are

the predisposing factors. The most common symptom is respiratory distress. The fishes


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often come to surface and preferably near aeration equipment for getting more oxygen.

Areas of haemorrhage with ulcers, which is very often circular in shape, are generally

observed. In advanced cases, slime can be observed all over the body surface. The affected

fishes become prone to secondary bacterial infections.

Among different crustacean species infecting brackishwater fishes, Caligus spp.

and Ergasilus spp. are important. Both of them affect Asian seabass. Affected fishes show

anorexia with sluggish behaviour. Erosion is observed in gill and skin leading to

secondary bacterial infection. High mortality generally takes place, if not treated in time.

13.3. Diseases of shrimps

13.3.1. White spot disease (WSD)

White spot disease caused by white spot syndrome virus (WSSV) is the most devastating

disease of shrimp. Taxonomically WSSV has been placed under the genus Whispovirus,

under family Nimaviridae. It is an enveloped double stranded DNA virus with

approximate genome size of 293 kb. This disease was first reported in Taiwan province of

China and mainland China during 1991-92. Later on, it was reported from many countries

of Asia, North America and South America. WSSV virus has a very wide host range of

aquatic crustaceans, including marine, brackish and freshwater prawns, crabs, crayfish and

lobsters. All penaeid shrimps including Tiger shrimp (Penaeus monodon), Pacific white

shrimp (Litopenaeus vannamei), Indian white shrimp (Fenneropenaeus indicus), banana

shrimp (Fenneropenaeus merguiensis), pacific blue shrimp (Litopenaeus stylirostris),

kuruma shrimp (Marsupenaeus japonicas) are highly susceptible to this disease. WSSV

virion can survive around 30 days in saline water at around 30ºC under laboratory

condition and is viable in freshwater ponds for at least 3–4 days. The virus can be

inactivated by heating at 50ºC for < 120 min or at 60ºC for < 60 min. All stages and ages

of prawn starting from egg to broodstock are susceptible to this disease. WSSV infection

in shrimp has been reported in almost all shrimp farming areas of India at both intensive

and traditional farming systems including bheries, pokkali etc.


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The virus can be transmitted through both vertically and horizontally. The stocking

of infected post-larvae is the most common source of infection of WSSV. In hatchery,

infected broodstock produces infected post-larvae. The disease is also transmitted from

contaminated environment like water, mud etc. The virus can remain infective in the pond-

bottom soil for almost 19 days. Different aquatic species including wild crabs, rotifers,

crayfish, Artemia, birds, algae, polychaetes, etc. may act as carriers and from there the

infection can be transmitted to the susceptible hosts. Stressful environments like sudden

change of temperature, salinity and pH, low dissolved oxygen etc. are predisposing factors

of this disease. The virus infects ectodermal and mesodermal tissues of the susceptible

host. At initial stages, the disease is characterized by lethargy, inappetence, crowding into

pond margin, loose cuticle, red to pink discolouration of the body and damage of antennae

and appendages. The most distinctive feature of this disease is presence of white spots of

different sizes on the inner side of the carapace and ultimately spread to all over the body

in advanced cases. Histological examination shows pathognomonic intra-nuclear inclusion

bodies in the affected tissues. Mortalities are generally very high and it may reach up to

100% within 3–7 days in case of heavy infection.

Diagnosis can be done by gross observation and different laboratory tests.

Detection of viral DNA by PCR is considered as most suitable and confirmatory

laboratory method for diagnosis of this disease. Other laboratory techniques for diagnosis

are dot blot hybridization, in-situ hybridization, histopathology and demonstration of viral

particle by electron microscopy. No reliable treatment method is available after onset of

the disease. Efficacies of different herbal extracts have been evaluated for their protective

role against WSSV with varying degree of success.

The most important control measure is use of specific pathogen free (SPF) shrimp.

PCR screening of seed and post-larvae before stocking is very important. The shrimp post-

WSSV infected P. monodon Carapace of WSSV infected shrimp


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larvae should be procured from reputed hatcheries. The strict biosecurity measures

including use of bird-fencing and crab-fencing should be employed. The stress of the

shrimp can be minimized by maintaining a good water quality and providing sufficient

aeration. High stocking density or over-crowding should be avoided. Before culture, pond

should be dried enough for at least 3 weeks. In case of outbreak, the water should be

bleached adequately and held for at least 7 days before releasing into environment. The

soil and water should be tested before next culture. No commercial vaccine is available

against WSSV till date. The experimental vaccine based on VP28 capsid protein has been

tried with varying success.

13.3.2. Infectious hypodermal and haematopoietic necrosis (IHHN)

This disease is caused by infectious hypodermal and haematopoietic necrosis virus

(IHHNV), which is a double stranded DNA virus with a very small genome size (around

3.9 kb). The virus is presently classified in the genus Betadensovirus under the family

Parvoviridae. The disease is also known as Runt deformity syndrome and is characterized

by irregular growth with cuticular deformities, deformed rostrum, opacity of striated

muscle, with reduced growth rate. In later stages, the shrimps become bluish in colour.

The affected shrimps rise slowly in the pond to the surface, become motionless, roll over

and slowly shrink with ventral side up. Symptoms generally appear at DOC 30. Major

target organs are gills and cuticle. Rate of mortality is not very high except in case of

pacific blue shrimp (L. stylirostris), in which the mortality may reach upto 90%. On

histopathology, the affected organs shows cytopathological changes with Cowdry Type A

intra-nuclear inclusion bodies. Both vertical and horizontal transmissions are possible.

13.3.3. Hepatopancreatic Parvovirus (HPV) infection

This disease is also caused by a parvovirus, which belongs to genus Brevidensovirus under

the family Parvoviridae. This is a single stranded DNA virus. HPV particle possesses

icosahedral capsid with an average diameter of 22 nm. HPV occurred in almost all species

of penaeid shrimps including P. monodon, L. vannamei, F. penicillatus and F. indicus.

Transmission is mainly through horizontal route by direct contact and contaminated water.

The disease has been reported in almost all shrimp growing countries both in intensive and

traditional culture systems. The shrimps are prone to the disease mostly during larval and

juvenile stages. Incidence of the disease in adult shrimp is very rare. The disease may

result in chronic mortalities during early larval and post-larval stages and stunted growth


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in juvenile stages. On histopathology, the tissue of hepatopancreas shows cells with

enlarged nuclei. Diagnosis of this disease can be done by PCR and histopathology.

13.3.4. Yellow head disease (YHD)

Yellow head disease is one of the devastating diseases of shrimps and is caused by a single

stranded RNA virus, which has been classified as Okavirus under family Roniviridae. The

genome size of this virus is around 26 kb. Transmission is mainly by horizontal route

through contaminated water or direct contact. The disease is characterized by yellow

discolouration of dorsal cephalothorax caused by yellow hepatopancreas visible through

translucent carapace. Different environmental factors like sudden change of pH and

salinity, drop in dissolved oxygen level may act as predisposing factors for this disease. At

initial stage, the disease is characterized by exceptional high feeding followed by cessation

of feeding. The moribund shrimps usually come near surface of pond. Then mass mortality

starts and usually entire crop is lost. YHV targets tissues of both ectodermal and

mesodermal origin including lymphoid organs, haemocytes, connective tissue, gut,

antennal gland, gonads, nerve tract and ganglia. In moribund shrimps, lymphoid organs

and gill are the most suitable organs for detection of viruses.

13.3.5. Taura syndrome

This is also a viral disease of shrimp caused by Taura Syndrome Virus (TSV), which is a

single stranded, non-enveloped, icosahedral shaped RNA virus with approximately 32 nm

in diameter. The disease was first reported in Ecuador. The disease has been reported in all

American shrimp growing countries, carribean countries, middle-east and south-east Asian

countries. Till date, the disease has not been reported in India. This virus has presently

been classified as Aparavirus under the family Dicistroviridae. TSV mainly affects pacific

white shrimp (L. vannamei) and pacific blue shrimp (L. stylirostris). The virus affects all

the life stages of shrimp. The virus replicates principally in the cuticular epithelium,

foregut, hind gut, gills, appendages, lymphoid organs, antennal gland, connective tissue

and haematopoietic tissue. The onset of disease generally occurs 15-40 days after

stocking. The affected shrimps show pale reddish colouration with pleopods being

distinctly red. TSV is also known as „Red tail disease‟. The shells become very soft and

weak, and shrimps cannot moult and mortality generally takes place during moulting.

Mortality rate varies from 40–100%. Transmission occurs both by horizontal and vertical

routes. Different species of birds and aquatic insects act as reservoir of this virus with sub-


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lethal infection. TSV has been frequently detected from the frozen shrimp in USA

imported from Latin American and South-east Asian countries. Diagnosis of this disease

can be done by reverse transcription-PCR, real time PCR, dot-blot hybridization and

ELISA.

13.3.6. Loose shell syndrome (LSS)

Loose shell syndrome is considered as one of the major disease problems in shrimp culture

of India and it causes a heavy economic losses. This disease was first reported in India in

1998. The incidence is more in summer than in winter. In India, the disease is more

prevalent in Andhra Pradesh state especially in the districts of East Godavari, West

Godavari and Nellore. LSS is also highly prevalent in Tamil Nadu. The disease is

characterized by flaccid sponge abdomen due to muscular dystrophy, shrunken

hepatopancreas and poor meat quality, which generally fetch reduced market price. Feed

conversion efficiency is generally reduced. On histopathology, the affected shrimps show

shrinkage of extensor and flexor muscle with occasional haemocytic infiltration. Molting

is impaired. The inflammation of hepatopancreatic tubules is also observed and the gap

between muscle and shell is generally increased. LSS is considered as a slow killer of

black tiger shrimp in India. The etiology of this disease is still not confirmed. Different

species of Vibrio has been isolated from affected shrimp. The involvement of a filterable

infectious viral agent has also been suspected for the disease. Maintenance of good

aquaculture practices including water quality parameters and adaption of strict biosecurity

measures may be of help in controlling this disease.

13.3.7. Black gill disease

Occurrence of this disease is more when too much plankton is present in water and

aeration is insufficient. This is also called fouling disease. High stocking density and

irregular probiotics use are also considered as predisposing factors for this disease. Gill

becomes black in colour and is generally colonized with different bacteria

(Flavobacterium, Cytophaga, etc.) and parasite (e.g., Zoothamnium spp.). The disease is

not generally fatal, but mortality occurs when this disease is coupled with low oxygen

level and presence of other stress factors. Addition of lime (quantity depends on pH),

water exchange and increase of duration of aeration may help in controlling this disease.


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13.3.8. Early mortality syndrome (EMS)

Among bacterial disease, this is the most devastating disease of shrimp and it often causes

100% mortality in case of L. vannamei. The disease also affects P. monodon. EMS is also

called as acute hepatopancreatic necrotic disease (AHPND). The etiology of the disease

has recently been confirmed as a particular strain of Vibrio parahaemolyticus, which bears

a specific plasmid. AHPND was first reported in Taiwan province of China and mainland

China in 2009 and later on reported from all shrimp growing countries of South-east Asian

region including Thailand, Vietnam, Malaysia etc. The disease affects shrimp post-larvae

20–30 days after stocking causes upto 100% mortality. In many cases, farmers are unable

to detect any shrimp in the pond after a month of stocking. According to Global

Aquaculture Alliance, the losses due to AHPND in shrimp industry are around US$ 1

billion. In the infected shrimp, hepatopancreas becomes pale with significant atrophy. The

shrimps also show soft shell and the gut with discontinuous content or no content. The

moribund shrimps usually shrink to bottom and die. Temperature fluctuation, high salinity

and high stocking density are the predisposing factors for AHPND. On histopathological

examination of smear from hepatopancreas, acute sloughing of tubular epithelial cells with

haemocyte infiltration is seen under Haematoxylin-Eosin staining. Histopathology of

hepatopancreas is considered is the most reliable method of diagnosis of EMS/ AHPND.

In addition to these, PCR has also been successfully employed for detection of specific

strain of V. parahaemolyticus causing AHPND. Strict surveillance should be done at farm

level for monitoring this disease.

13.3.9. Vibriosis

Vibriosis is in shrimps caused by different species of Vibrio including V.

parahaemolyticus, V. alginolyticus, V. mimicus, V. harveyi, V. fischeri, V. litoralis, V.

metschnikovii etc. Water bodies, especially the brackishwater environment are the normal

habitat of different species of Vibrio. But they act as opportunistic pathogens of cultured

shrimp and affect shrimps during different environmental stresses including mechanical

injury, higher salinity, increased level of ammonia, nitrite and nitrate, low dissolved

oxygen, higher stocking density, sudden change of pH, etc. Different shrimp hatcheries

frequently encounter the problem of vibriosis. In case of larval stage, diagnosis of vibriosis

can be done by microscopic demonstration of bacterial rods in haemolymph. In grow-out

culture, this disease is characterized by melanised nodules in the gills, opacity of muscle,

red discolouration of the appendages etc. The affected shrimps swim weakly and


146

abnormally, and gather along edges of pond. Haemolymph of the affected shrimp does not

clot or clot at very slow rate. Different species of Vibrio can be isolated from haemolymph

and hepatopancreas by plating on TCBS agar and Zobell marine agar. Specific species of

Vibrio can be identified by different biochemical tests or by 16S rRNA sequencing. Some

species of Vibrio like V. harveyi, V. fischeri are considered as luminescent bacteria and

they emit luminescence in dark. The luminescence can be demonstrated by preparing a

smear from haemolymph and observation in dark. In case of heavy infection, the

luminescence can be seen if the haemolymph is observed in dark. Some species of Vibrio

also produces „white fecal syndrome‟ leading to poor water quality and loss of production.

In shrimp hatcheries, some management practices like batch culture of larvae,

systemic disinfection between stocking, proper disinfection of incoming water of hatchery

system, proper disinfection of equipment, lower larval stocking density, control of water

temperature to avoid fluctuation, periodic water exchange to reduce the bacterial load,

rinsing of larvae with clean water and proper management to reduce cross-transfer of

water can reduce the risk of vibriosis. In grow-out pond, this disease can be controlled by

application of different probiotics, application of neem leaves at 20 kg/ ha, fertilization of

pond with sucrose (20 kg/ ha), etc. Addition of garlic paste (5–10 g of garlic/ kg of feed)

and leaves of Cantella asiatica (Indian penny wort) (10 g/ kg of feed) in feed have

recently been found to be very effective in controlling vibriosis in grow-out pond.

Application of different probiotics (e.g., superbiotic, superPS, zymetin, mutagen, etc.) and

immunostimulants (Heat killed Vibrio or Vibrio bacterin, yeast β-glucan, Vibrio

lipopolysaccharide etc.) are also very helpful to combat this disease.

13.4. Common general practices for treatment and control of diseases in

brackishwater aquaculture systems

13.4.1. Best management practices (BMPs)

Maintaining health of aquatic organisms largely depends on the soil and water qualities.

Therefore, care should be taken from the very beginning to select a proper site for

aquaculture practice. Waste materials are generated during the culture practice and hence,

sufficient gap should be there between the culture cycles for proper preparation of pond.

Stress is the main factor to initiate disease and this can be avoided to a large extent

through BMPs. Details regarding soil, water qualities as well as BMPs are mentioned

separately elsewhere in this manual and readers are requested to refer those.


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13.4.2. Biosecurity

Infectious diseases are major cause for crop loss in any aquaculture system. Utmost care

should, therefore, be taken to prevent spread of such causative agents. Source water, seed,

equipment, workers and invasive organisms are the main sources of spread of organisms

like bacteria, virus and fungi. Adherence to biosecurity measures ensures disease

prevention to a large extent.

13.4.3. Genetic selection

Inbreeding depression may decrease the disease resistance capacity and therefore,

selective breeding should be adopted in aquaculture for seed production. After

determining the disease resistance markers, animals can also be selected for the production

of totally disease resistance progenies. Where complete resistant strain production is not

possible, care should be taken to produce at least specific pathogen free (SPF) stocks as

has been tried for L. vannamei. As in this case, seed will be free from major disease

causing agents, BMPs can be followed to get a successful harvest.

13.4.4. Disease treatment

Though prevention is better than treatment, many times it becomes difficult to avoid

disease occurrence. During that time effective treatment is necessary to avoid mortality

and thereby crop loss. A wide range of antibiotics are used to control bacterial diseases.

However, indiscriminate use of antibiotics develops drug resistance strains and

subsequently it becomes difficult for control. This also poses serious health problem for

human beings and terrestrial animals. Many of the antibiotics used for human medicine are

banned for aquaculture practice. Only few of the antibiotics such as oxytetracycline are

recommended. Some of the emerging pathogens like AHPND specific V.

parahaemolyticus develop quick resistance to those antibiotics. Therefore, use of

antibiotics for control of bacterial diseases in aquatic system is not promising. Several

other disinfectants such as acriflavin, iodophor, potassium permanganate, sodium

hypochlorite, copper sulfate, formalin etc. have been found to be effective in controlling

bacterial, fungus or parasite load. Physical methods such as management of temperature,

pH or use of ultraviolet light are also found to be very effective against specific pathogens

of both bacteria and virus.


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13.4.5. Vaccines

For organisms with well-developed immune system as found in finfishes, use of vaccines

against specific pathogens has been observed to be effective. Many of these vaccines have

been tested in laboratories and a few have been commercialised. Majority of these

commercial vaccines have been used for salmon aquaculture. Live attenuated, heat killed

and recombinant vaccines have been used for effective control of different fish bacterial

and viral pathogens. However, with further modification, a single injection can now

protect against multiple pathogens. One of such vaccine in the name of „AQUAVAC PD3‟

is now being used in the UK for salmon to control three different diseases. Similarly, a

large number of adjuvants have been developed for effective delivery and function of

various fish vaccine. Unfortunately for aquatic invertebrates such as crustaceans that

primarily rely on non-specific immune system, development of an effective vaccine has

not been successful.

13.4.6. Immunostimulants

Non-specific immune system is for primary defence against a wide range of pathogens

both in vertebrates and invertebrates. This non-specific immune system of crustaceans

system can be stimulated through various microbial and plant based products to provide

better protection. This is particularly important for invertebrates such as aquatic

crustaceans where non-specific immune system is the major disease protecting component.

Lipopolysaccharide (LPS) from Gram negative bacteria and peptidoglycan/ β-glucan from

Gram positive bacteria/ yeast are widely used immunostimulants. Different plant based

products with proven medicinal properties have been successfully used as

immunostimulants both for finfishes and shellfishes. In addition to providing protection

against diseases, these immunostimulants have also been found useful to provide better

growth.

13.4.7. RNA interference

This is a recently developed method which has been very useful for the control of several

pathogens. It has been particularly promising for the control of viral diseases where in

many cases treatments through medicines are not possible. Specific virulence genes of the

pathogens are targeted to develop short RNA fragments (either single or double stranded)

and this is either injected or supplied through oral route after modification. This brings


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degradation of the pathogen through post translational modification. The RNAi system has

been found to be functional both in finfishes and crustaceans such as shrimp.

13.4.8. Quorum quenching

Quorum sensing is a method of communication for several groups of bacterial pathogens

such as V. harveyi (shrimp luminescent disease) and V. parahaemolyticus (shrimp

AHPND) to exhibit the virulence, biofilm formation or antibiotic resistance. To have this

communication, the bacteria require reaching a specific population and then produce

specific molecules such as N-acyl Homoserine Lactone (AHL) in case of Gram negative

bacteria. Some of the components produced by several organisms and plants are found to

inactivate the specific quorum sensing activators. In that case, the bacteria cannot produce

the required virulence to bring disease.

13.4.9. Bio-control of pathogens

13.4.9.1. Probiotics

A group of „good bacteria‟, those are known to improve the host immune system and

thereby provide good health when consumed, are called as probiotics. When consumed,

these bacteria go and colonize in the gut. In this way, they occupy the space and do not

allow the pathogenic bacteria to settle down. They also produce specific molecules which

stimulate the immune system. Two kinds of probiotics are used in aquaculture system- gut

probiotics and water probiotics. Gut probiotics perform the function of replacing the

pathogenic bacteria and stimulating the immune system. Whereas, the water probiotics

helps in increasing the diversity of good bacteria in water and thereby do not allow the

multiplication of pathogenic bacteria. These bacteria are also known to secret extracellular

products that have inhibitory effect against harmful bacteria. A number of probiotics

products, consisting of several bacteria species such as Lactobcillus sp., Bacillus sp.,

Pseudomonas sp. etc either as single species or as consortium are available for the use in

both fish and shellfish culture.

13.4.9.2. Phage therapy

Bacteriophages are a group of virus that specifically infect and kill bacteria. Many of these

bacteriophages are host specific, while others have broad spectrum activity. Phage therapy

is very promising for aquaculture practice as this can replace the use of antibiotics which

are otherwise not advocated for aquaculture use.


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Further readings

Alavandi, S.V., Babu, T.D., Abhilash, K.S., Kalaimani, N., Chakravarthy, N.,

Santiago, T.C. and Vijayan, K.K., 2008. Loose shell syndrome of farmed Penaeus

monodon in India is caused by a filterable agent. Diseases of Aquatic Organisms 81:

163-171.

Azad, I.S., Shekhar, M.S., Thirunavukkarasu, A.R., Poornima, M., Kailasam, M.,

Rajan, J.J.S., Ali, S.A., Abraham, M. and Ravichandran, P., 2005. Nodavirus infection

causes mortalities in hatchery produced larvae of Lates calcarifer: first report from

India. Diseases of Aquatic Organisms 63: 113-118.

Brudeseth BE1, Wiulsrød R, Fredriksen BN, Lindmo K, Løkling KE, Bordevik M,

Steine N, Klevan A, Gravningen K. (2013). Status and future prospective of vaccines

for industrialized fin fish farming. Fish and shellfish Immunology 35: 1759-68

CIBA, 2014. Central Institute of Brackishwater Aquaculture. Training manual on

health management practices of finfish and shelfish of brackishwater environment.

CIBA special publication series no. 74.

FAO. Prevention and control of fish diseases. In: FAO corporate document repository:

Selected aspects of warmwater fish culture. Chapter 5. Accessible through

http://www.fao.org/docrep/field/003/t8389e/T8389E05.htm

Flegel, T.W., Lightner, D.V., Lo, C.F. and Owens, L., 2008. Shrimp disease control:

past, present and future, pp. 355-378. In Bondad-Reantaso, M.G., Mohan, C.V.,

Crumlish, M. and Subasinghe, R.P. (eds.). Diseases in Asian Aquaculture VI. Fish

Health Section, Asian Fisheries Society, Manila, Philippines. 505 pp

Kalaimani, N., Ravisankar, T., Chakravarthy, N., Raja, S. Santiago, T.C. and Ponniah,

A.G., 2013. Economic losses due to disease incidences in shrimp farms of India.

Fishery Technology 50: 80-86.

Karunasagar, I., Karunasagar, I. and Otta, S.K., 2003. Disease problems affecting fish

in tropical environments. Journal of Applied Aquaculture 13: 231-249.

Lightner, D.V., 2011. Status of shrimp diseases and advances in shrimp health

management, pp. 121-134 In: Bondad-Reantaso, M.G., Jones, J.B., Corsin, F. and

Aoki, T. (eds.). Diseases in Asian Aquaculture VII. Fish Health Section, Asian

Fisheries Society, Selangor, Malaysia. 385 pp.

http://www.ncbi.nlm.nih.gov/pubmed/?term=Brudeseth%20BE%5BAuthor%5D&cauthor=true&cauthor_uid=23769873

http://www.ncbi.nlm.nih.gov/pubmed/?term=Wiulsr%C3%B8d%20R%5BAuthor%5D&cauthor=true&cauthor_uid=23769873

http://www.ncbi.nlm.nih.gov/pubmed/?term=Fredriksen%20BN%5BAuthor%5D&cauthor=true&cauthor_uid=23769873

http://www.ncbi.nlm.nih.gov/pubmed/?term=Lindmo%20K%5BAuthor%5D&cauthor=true&cauthor_uid=23769873

http://www.ncbi.nlm.nih.gov/pubmed/?term=L%C3%B8kling%20KE%5BAuthor%5D&cauthor=true&cauthor_uid=23769873

http://www.ncbi.nlm.nih.gov/pubmed/?term=Bordevik%20M%5BAuthor%5D&cauthor=true&cauthor_uid=23769873

http://www.ncbi.nlm.nih.gov/pubmed/?term=Steine%20N%5BAuthor%5D&cauthor=true&cauthor_uid=23769873

http://www.ncbi.nlm.nih.gov/pubmed/?term=Klevan%20A%5BAuthor%5D&cauthor=true&cauthor_uid=23769873

http://www.ncbi.nlm.nih.gov/pubmed/?term=Gravningen%20K%5BAuthor%5D&cauthor=true&cauthor_uid=23769873


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Loka, J., Janakiram, P., Geetha, G.K., Sivaprasad, B. and Kumar, M.V., 2012. Loose

shell syndrome (LSS) culture Penaeus monodon- microbiological and

histopathological investigations. Indian Journal of Fisheries 59: 117-123.

MPEDA (2015). Marine products export crosses US$ 5 billion in 2013-14. The Marine

Products Export Development Authority. Accissible online through

http://www.mpeda.com/inner_home.asp?pg=trends.

OIE, 2009. Epizootic ulcerative syndrome. In: Manual of Diagnostic Tests for Aquatic

Animals. Chapter 2.3.2. Accessible online through

http://web.oie.int/eng/normes/fmanual/2.3.02_EUS.pdf

OIE, 2012. White spot disease. In: Manual of Diagnostic Tests for Aquatic Animals.

Chapter 2.2.6 Accessible online through

http://www.oie.int/fileadmin/Home/eng/Health_standards/aahm/current/2.2.06_WSD.p

df

OIE, 2015. Infectious hypodermal and haemopoietic necrosis. In: Manual of

Diagnostic Tests for Aquatic Animals. Chapter 2.2.2 Accessible online through

http://www.oie.int/fileadmin/Home/eng/Health_standards/aahm/current/2.2.02_IHHN.

pdf.

OIE, 2015. Taura syndrome. In: Manual of Diagnostic Tests for Aquatic Animals.

Chapter 2.2.5 Accessible online through

http://www.oie.int/fileadmin/Home/eng/Health_standards/aahm/current/2.2.05_TAUR

A.pdf

Toranzot, A.E., Magarinos, B. and Romalde, J.L., 2005. A review on main bacterial in

mariculture systems. Aquaculture 246: 37-61.

Vijayan, K.K., Raj, V.S., Balasubhramanium, C.P., Alavandi, S.V., Sekhar, V.T. and

Santiago, T.C., 2005. Polychaete worms- a vector for white spot syndrome virus

(WSSV). Diseases of Aquatic Organisms 63: 107-111.


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Fish Health Management in Brackishwater

Aquaculture with Special Reference to

Emerging Diseases

K.V. Rajendran, Sanjoy Das* and P.K. Patil



14.1. Introduction

Aquaculture is recognized as the fastest growing food-production sector, which not only

provides food but generate employment opportunities. Indian aquaculture is dominated by

marine shrimp both in terms of production and export earnings. However, like any other

food producing sector, diseases are the major limiting factors in aquaculture production in

many parts of the world including India. In India, the gross national loss due to shrimp

diseases during 2006-08 was estimated as Rs.1022 crore (Kalaimani et al., 2013). In

brackishwater systems, shrimp culture is paralyzed by various diseases, among which

white spot disease (WSD) caused by white spot syndrome virus (WSSV) is the most

dreaded one. The disease continues to cause heavy mortality resulting in huge economic

loss to the farmers.

Although a single virulent pathogen can cause massive mortality in aquaculture

system, most often diseases in aquaculture are an expression of complex interaction

between the host, pathogen and environment, and even the less virulent pathogen can play

a crucial role in disease outcome in presence of stressed environmental conditions.

Although unregulated expansion and intensification of aquaculture in many developing

countries has resulted in the rampant disease outbreaks, poor water quality, unrealistic

stocking density, poor pond and feed management are the major reasons for the disease

outbreaks originating from unregulated movement of live aquatic animals and associated

introduction or transfer of pathogens. It is in this background that health maintenance or

management is now considered as one of the most important aspects of aquaculture

development and management.

14


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14.2. Components of health management

14.2.1. Diagnostics

A specific, sensitive and rapid diagnostic tool is essential for any health management

programme. However, disease diagnostic procedures in aquaculture have advanced from

visual recognition and microscopic characterization of pathogens to molecular

characterization and probe-based diagnosis. These advancements have helped aquaculture

sector in a big way. These tools help not only for farm-level screening and monitoring of

cultured animals but also for disease surveillance, biosecurity measures and international

trade. However, development of efficient diagnostic assays for endemic as well as exotic

pathogens is significant to achieve a kind of disease preparedness. Further, for

international trade of frozen as well as live aquatic animals, diagnostic tools specified by

international agency such as OIE is a mandatory requirement. Therefore, it is imperative

that aquatic animal health laboratories in the country would focus on developing,

standardizing and refining the diagnostic tools for endemic, emerging and exotic diseases

of different aquaculture species. Among the diagnostic techniques, PCR-based diagnosis is

the most reliable and widely used one. Accordingly, PCR-based diagnostics for all the

viral pathogens reported from shrimp have been developed and standardized.

14.2.2. Health monitoring

The fundamental reason for the constant monitoring of health is to detect early stages of

disease problem and respond before a disease outbreak become uncontrollable. Further,

since the changes in the health of cultured animals will be apparent only over a period of

time, and the changes would become obvious only when there is a combination of

observation on the general appearance, feed consumption, growth, water quality etc.

However, there would be difficulty in getting an accurate picture of the situation even after

a constant monitoring, as in most disease cases the external signs are non-specific and it

would be difficult to get enough information about the environmental problems that would

predispose the animals to disease as the environment in a pond would constantly fluctuate

and it is not uniform. Nevertheless, it needs to be confirmed that conditions in the culture

system are suitable for the animal‟s survival and healthy growth. Therefore, it is

imperative that a sound health management protocol should include a stringent and

constant health monitoring and accurate record keeping.


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14.2.3. Health management

An effective health management protocol ensures not only improved production, but also

reduces the risk associated with diseases. A comprehensive health management focuses on

all critical control points along the production pathway. These include all levels of

aquaculture activities from the production unit (hatchery, pond, tank, cage etc.), farm,

local (districts/ zones), state to the national and international level. Further, an effective

health management programme comprises steps and control measures that are carried out

on a daily-basis throughout the year. Overall, a science-based health management

procedure includes seasonal factors and crop-planning, pond-preparation, post-larvae/fry

selection and stocking process, water quality management, pond bottom management, feed

management, fish health monitoring, farm record keeping, dealing with disease outbreaks,

if any, and appropriate use of chemicals, if necessary. However, even the stringent health

management procedure may not be able to eliminate the risk of diseases or mortality

completely.

14.2.4. Biosecurity

Biosecurity is defined as the measures and methods adopted to secure a disease free

environment in all phases of aquaculture practices (i.e., hatcheries, nurseries, grow-out

farms) for improved profitability. This is an utmost essential to maintain security of an

aquaculture facility by preventing the entry or reducing the chances of entry of disease

causing organisms. Further, protocols also involve preventing the spread of pathogens, if a

facility is infected, from one system to another. Common biosecurity measures include

proper egg disinfection, control of vertical disease transmission, strict sanitation measures,

control of movement of people and vehicle, water treatments and effluent treatment, clean

feed, proper disposal of dead animals etc.

14.3. Diseases/ pathogens

There are several infectious diseases reported in cultured finfish species. However, only

limited number of serious pathogens has been recorded from brackishwater fishes.

According to World organization for animal health (OIE), there are 12 notified pathogens,

of which 10 are viruses and one parasite and other is caused by an oomycete. Among

these diseases, only two diseases are reported from India: Epizootic ulcerative syndrome

(EUS) caused by the oomyceteous fungus Aphanomyces invadans and viral

encephalopathy and retinopathy (VER) caused by nodavirus.


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14.3.1. OIE-listed diseases of finfishes

i) Epizootic haematopoietic necrosis

ii) Infection with Aphanomyces invadans (Epizootic ulcerative syndrome)

iii) Infection with Gyrodactylus salaris

iv) Infectious haematopoietic necrosis

v) Infection with Infectious salmon anaemia virus

vi) Infection with salmonid alphavirus

vii) Koi herpesvirus disease

viii) Red sea bream iridoviral disease

ix) Spring viraemia of carp

x) Viral haemorrhagic septicaemia

xi) Oncorhynchus masou virus disease

xii) Viral encephalopathy and retinopathy

14.3.1.1. Viral encephalopathy and retinopathy

Viral encephalopathy and retinopathy (VER), otherwise known as viral nervous necrosis

(VNN), is a serious disease of several marine and brackishwater fish species. The disease

is characterised by vacuolating lesions of the central nervous system and the retina which

result in large-scale mortality. The causative agent of the disease is a Betanodavirus. Lates

calcarifer (Asian seabass) is one of the most susceptible species. The disease mainly

affects larval and juvenile stages. However, mortality has been recorded in adult fish also.

The mortality rate is age-dependent. When larval stages are affected, highest mortality,

often reaching 100%, is observed. However, compared to the early stages, mortality is

found to be less in juveniles and older fish. The virus gets transmitted both horizontally

and vertically. Further, the virus is highly resistant and can survive in the aquatic

environment for long time at low temperature. Screening of broodstock for getting virus-

free stock in the hatchery will be the best option for control. Disinfection of egg and larvae

is found to be effective. Washing of fertilised eggs with ozone-treated sea water or

treatment of rearing water with ozone or chlorination is an effective method.

OIE list contains 10 pathogens infecting crustaceans. These include 8 viral

pathogens infecting penaeid shrimps, one virus of freshwater prawn, Macrobrachium


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rosenbergii and an oomyceteous fungus (Aphanomyces astaci) infecting crayfish. Out of

these, white spot syndrome virus (WSSV) which causes white spot disease (WSD)

continues to be the most serious disease in the majority of the shrimp growing countries in

the region. However, Taura syndrome virus (TSV), which is originally a virus of

Litopenaeus vannamei, first reported from Ecuador, has been reported from other regions

also, especially from China, Indonesia and Thailand.

14.3.2. OIE-listed diseases of crustaceans

i) Crayfish plague (Aphanomyces astaci)

ii) Infectious hypodermal and haematopoietic necrosis (NB: version adopted in May

2015)

iii) Infectious myonecrosis

iv) Necrotising hepatopancreatitis (NB: version adopted in May 2015)

v) Taura syndrome (NB: version adopted in May 2015)

vi) White spot disease

vii) White tail disease

viii) Infection with yellow head virus (NB: version adopted in May 2015)

ix) Spherical baculovirus (Penaeus monodon-type baculovirus)

x) Tetrahedral baculovirosis (Baculovirus penaei)

14.3.2.1. White spot disease

White spot disease (WSD) caused by WSSV is the most virulent pathogen of penaeid

shrimps. Infected animals show white spots/ patches on the exoskeleton, appendages and

inside the epidermis. Other signs of WSD include lethargy, sudden reduction in feed

consumption, red discoloration of body and appendages and loose cuticle. Mortality

reaches 100% within a week depending upon the severity of infection. The virus has a

very wide host-range infecting almost all the crustaceans and there are reports indicating

that polychaete worms can also harbour this virus. All the life-stages are susceptible to the

infection and the virus can be transmitted both horizontally and vertically. In the host, the

virus replicates in almost all the organs. There is no effective field-level anti-viral

treatment available for the control of the virus, however, a number of husbandry/

management measures have been used successfully to manage WSD, such as avoiding


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stocking in the cold season, use of specific pathogen-free (SPF) or PCR-negative seed

stocks, and use of biosecure water and culture systems.

14.4. Emerging diseases

During the last decade, several new diseases have emerged and caused either heavy

mortality or debilitating production losses through retarded growth of cultured animals.

This emergence has been attributed to large-scale intensification, increased transboundary

movement of aquatic animals and products, and increased stress on aquatic environment.

Apart from the new or unknown diseases, occurrence of existing diseases in new host

species and new geographic location or known diseases with increased virulence or

mutation or with different clinical manifestation are also considered to be in the category

of emerging diseases. Emerging diseases result in catastrophic mortality or often result in

production loss due to growth retardation of cultured species. Emerging new diseases are

challenging problems because of many factors: a) difficulty or delay in developing

confirmatory diagnostic tools; b) poor knowledge on the host susceptibility and host-

range; c) lack of knowledge on the epidemiological factors such as mode of transmission,

reservoirs and carrier hosts etc. Following are some of the diseases which can be

categorized under emerging diseases:

14.4.1. Early mortality myndrome (EMS)/ Acute hepatopancreatic necrosis disease

(AHPND)

The EMS/ AHPND disease typically affects shrimp post-larvae within 20–30 days after

stocking and frequently causes up to 100% mortality. The causative agent of EMS/

AHPND has been reported to be a bacterium, a specific strain of Vibrio parahaemolyticus

bearing a particular plasmid. Clinical signs reported include slow growth, corkscrew

swimming, loose shells and pale colouration. Affected shrimps also consistently show an

abnormal hepatopancreas (shrunken, small, swollen or discouloured). Histologically, the

manifestation is limited to changes in the hepatopancreas, which include massive necrotic

changes. The disease has been reported to cause significant losses in China, Vietnam,

Malaysia and it has also been reported from Thailand. However, there are no confirmed

reports of EMS from India.

14.4.2. White muscle syndrome/ Infectious myonecrosis

Severely infected shrimps become lethargic during or after stressful events such as

capturing using cast-netting, feeding, sudden changes in temperature and drop in salinity.


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However, shrimp will have full gut. In acute infection, animals show extensive whitish

necrosis in skeletal muscles, especially in the distal abdominal segments and tail.

Lymphoid organs show excessive hypertrophy. These clinical signs develop during or

after stressful experience capturing, feeding and sudden changes in temperature and

salinity. Necrotic areas may appear reddened in some animals. Severe infection results in

morbidity and high mortality which continues for several days. The causative agent is an

RNA virus known as Infectious Myoncrosis Virus (IMNV).

14.4.3. Muscle necrosis of Litopenaeus vannamei caused by Penaeus vannamei

nodavirus (PvNV)

The disease resembles IMNV infection where white opaque lesions are noticed in the tail

region. Histopathological changes include multifocal necrosis and haemocytic fibrosis in

the skeletal muscle. Basophilic cytoplasmic inclusions in striated muscle, lymphoid organ

and connective tissues are also observed. The disease also causes lymphoid organ

spheroids. The causative agent has been identified as Penaeus vannamei nodavirus

(PvNV). PvNV does not cause serious mortality, however, affects survival in grow-out

ponds. Sporadic mortality of infected shrimps has been recorded when they are under

environmental stress such as crowding (stocking density > 50/ m2) and high temperature

(> 32°C) and survival decreased to 40% and increased food conversion ratio. The disease

has not been reported from India.

14.4.4. Running mortality syndromes (RMS)

The term running mortality syndrome (RMS) has been used to describe prolonged chronic

mortality during a crop. The mortality starts 1–2 months after stocking and becomes

severe during later part of summer crop. The exact cause of the disease has not been

identified; however, reports indicate the involvement of multiple causes such as covert

mortality disease caused by cover mortality nodavirus (CMNV), white muscle syndrome,

white gut/ faeces syndrome and white patch disease. There are reports of RMS from

cultured L. vannamei from India; however, no definite aetiology has been identified.

14.4.5. White gut/ faeces syndrome

This has been observed in cultured P. monodon and L. vannamei and the typical sign is the

appearance of faecal string-like bodies in the gut. It appears like vermiform bodies that

resemble gregarines within the hepatopancreatic tubules, at the hepatopancreas-stomach-

midgut junction and in the midgut. It generally occurs approximately from 2 months of


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culture and initially the causative agent has been reported as gregarines and the condition

is described as white faeces syndrome (WFS). The disease has been reported to cause 10–

15% production loss due to decreased survival and smaller harvest size of shrimp.

Although the causative organisms has not been identified, latest report shows that the

vermiform bodies superficially resembling gregarines arise from transformation, sloughing

and aggregation of hepatopancreatic microvilli and this will result in retarded growth and

may predispose shrimp to opportunistic pathogens. The disease has also been recorded

from cultured L. vannamei in India.

14.4.6. Monodon slow growth syndrome (MSGS)

This is a viral disease of P. monodon and is caused by a single stranded RNA virus called

as Laem-Singh virus (LSNV). MSGS condition in P. monodon is characterized by

abnormally slow growth and wide length and weight variation between individual shrimp

at same culture period. The affected shrimps exhibit unusual dark colour, bright yellow

marking, brittle antennae and bamboo-shaped abdominal segment. The average daily

weight gain is sometimes even less than 0.1 g per day. This disease was first reported in

Thailand in 2002. The virus can be detected in lymphoid organs, heart and other tissue of

affected shrimp. The major pathological lesion observed in this disease is retinopathy,

which is considered as one of the reason of stunted growth.

14.4.7. Muscle cramp syndrome (MCS)

This is an emerging disease of L. vannamei and is common, especially when the stocking

density is high. High water temperature, sudden increase in salinity and low dissolved

oxygen level are the predisposing factor for this disease. Affected shrimps exhibit anorexia

and bending of body in comma shape. Sometimes, the symptoms disappear following drop

of environmental temperature. Increase of aeration also solves this disease problem to

some extent.

14.4.8. White patch disease (WPD)

This is also an emerging disease of L. vannamei and is caused by a bacteria Bacillus

cereus. The symptoms are focal to extensive necrotic area in the striated tail muscle and

abdominal muscle. The necrotic areas appear as opaque white patch. In advanced stage,

the white area changed into black spots. The infected shrimps exhibit pale white muscle,

whitish blue discolouration of the body, loss of appetite, roughness of whole body surface


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etc. The mortality rate is sometimes as high as 100%. Very often dead shrimps display

empty exoskeleton.

14.5. Conclusion

Control and prevention of diseases in aquaculture is largely a function of management.

This could be achieved by a holistic science-based strategy. As the brackishwater

aquaculture has transformed from traditional and semi-intensive culture of native species

of shrimp to an intensive level of culture of exotic/ non-native species, increased emphasis

needs to be given for quarantine and biosecurity. The experience shows that even if

specific pathogen-free stock is available for culture which can help in preventing dreaded

diseases like WSD, breach of biosecurity protocols leads to occurrence of WSD in

cultured L. vannamei. Further, there is an increased occurrence of new and emerging

diseases which is posing great challenge to the sustainability of brackishwater aquaculture.

Further readings

FAO. Fish health management in aquaculture. Fisheries and Aquaculture Department.

Food and Agriculture Organization of United Nation. Accessible through

http://www.fao.org/fishery/topic/13545/en

Flegel, T.W. Monodon slow growth syndrome and Laem-Singh virus (LSNV)

retinopathy Disease card. NACA. Accessible online through

http://library.enaca.org/Health/DiseaseLibrary/lsnv_msgs_disease_card.pdf

Gunulan, B., Soundarapandian, P., Anand, T., Kotiya, A.S. and Simon, N.T., 2014.

Disease occurrence in Litopenaeus vannamei shrimp culture systems in different

geographical regions of India. International Journal of Aquaculture 4: 24-28.

Kalaimani, N., Ravisankar, T., Chakravarthy, N., Raja, S. Santiago, T.C. and Ponniah,

A.G., 2013. Economic losses due to disease incidences in shrimp farms of India.

Fishery Technology 50: 80-86.

Walker, P.J., Winton, J.R., 2010. Emerging viral diseases of fish and shrimp.

Veterinary Research 41: 51.


161

Application of Genetics and Biotechnological

Tools in Aquaculture

M.S. Shekhar and K. Vinaya Kumar


15.1. Introduction

Globally, one of the major contributions of the science of genetics and breeding is the

genetic improvement that was brought into the economic traits of candidate species.

Conventional selection programmes have contributed to increased food production

globally. Genetic improvement programmes are critical to achieve sustainable aquaculture

with limited resources of feed, water and land. Along these the science of genetics was

used to develop marker suites for parentage assignment, to find quantitative trait loci

(QTL) for traits that are difficult to measure or lowly heritable or express late in life, to

understand population structure, to generate linkage maps, to develop markers for species

identification etc. The other applications of biotechnology in aquaculture includes

bioprospecting of aquatic resources, for the unique and novel bioactive compounds that

can be used in the development of commercial, healthcare and biomedical applications for

community benefit. Much attention is being given to discover effects of nutrients in the

novel metabolic and biochemical pathways using modern techniques associated with

genomics and proteomics and one of these modern areas of study is nutrigenomics. The

critical areas where biotechnological techniques have a major impact in aquaculture are

covered in this article.

15.2. Selection programmes

Genetic improvement through selection has been an important contributor to the dramatic

advances in agricultural productivity that have been achieved in recent times (Dekkers and

Hospital, 2002). Genetic improvement of any population of a species involves periodic

evaluation, selection and culling of animals. Especially in aquaculture sector, any new

species identified for genetic improvement programme should be domesticated first and

reproduction of that species should be mastered to perfection. Otherwise, limited numbers

of founders at the beginning of domestication process could lead to reduced genetic

variability in hatchery broodstock populations. Unlike livestock which have been

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domesticated years ago, aquatic species are yet to be domesticated. Genetic improvement

programmes for sustainable aquaculture production are reflected in FAO‟s Code of

Conduct of Responsible Fisheries (FAO, 1995). Genetic improvement is possible only

when breeding programmes are well-designed which leads to substantial response in the

character or trait under selection. Some examples which come to our mind especially

when dealing with aquatic species is the genetic improvement programme of Atlantic

salmon, rainbow trout, Nile tilapia, rohu carp and Pacific white shrimp. Several shrimp

lines selected for their resistance to pathogens or for their growth rates are now

commercially available and certified free of the four following viruses: Taura Syndrome

Virus, Infectious Hypodermal and Hematopoietic Necrosis Virus, White Spot Syndrome

Virus, and Yellow Head Virus. A major breakthrough in the application of genomics to

the genetic improvement of Atlantic salmon is the finding of QTL for Infectious

Pancreatic Necrosis disease. The eggs produced by the homozygous fish possessing highly

resistant QTL have been sold as „IPN-QTL‟ eggs. All these programmes have revealed the

effectiveness of genetic selection in aquaculture when economically important traits are

selected for. However, it is important to note that aquaculture production is using only a

miniscule portion of genetically improved species, be it finfish or shellfish. A considerable

portion of aquaculture production depends largely on species that have not undergone any

systematic genetic improvement. Genetic improvement programmes are of long-term

nature and the inputs in terms of money, labour and personnel are very substantial. There

has however been a school of thought that unless genetic improvement programmes are

initiated, one cannot increase aquaculture production.

The economically important traits in fish species are quantitative in nature that are

controlled by large number of genes called minor genes or polygenes, wherein, very few

genes have relatively large effects with many others having smaller effects in the overall

expression of the trait. In traditional genetic improvement programs, selection of animals

is carried out on the basis of observed phenotypes recorded on the animals themselves or

their direct relatives or their collateral relatives. Selection efforts increase the frequency of

beneficial over non-beneficial alleles in the population to improve the population mean for

the trait under selection.

15.3. Functional studies

All over the world, the sequence related information generated has been deposited and

classified under different heads as per GenBank data. The EST (Expressed Sequence Tag)


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database contains sequence records that are typically short single-pass reads from cDNA

libraries. These EST databases were generated and exploited by researchers for discovery

of novel genes, differential gene expression studies and identification of genes expressed

in a particular organ, tissue or cell type or at various physiological states related to salinity

stress, immunity, growth and reproduction. The EST databases are the major resources in

planning functional studies in fish and shellfish to unravel important genes related to

various commercially important traits as very few species genome is wholly sequenced.

The EST databases were also used to document SNPs and microsatellites in various

species. There is great potential for using genomic information in comprehending growth

and reproductive parameters for cultured species and using this in marker assisted

selection programmes.

15.4. Linkage maps

A linkage map of a species has molecular markers placed in an order along the length of

the chromosomes in the genome of that species. Linkage map indicates the position and

relative genetic distances between markers along the chromosomes. The distance between

markers is estimated by the principles explained for the first time by Arthur Sturtevant

(Sturtevant, 1913). Two mapping functions, Kosambi mapping function and Haldane

mapping function are commonly used for converting recombination frequency in to map

units called centiMorgans.

The genotype information of polymorphic markers in mapping populations is

subjected to linkage analysis for the construction of linkage map. Popular software

packages used for construction of linkage maps in aquaculture species include

CARTHAGENE, CRIMAP, JOINMAP, LINKMFEX, MAPCHART, MAPINSECT 1.0,

MAPMAKER and MAPMANAGER. Except JOINMAP, all others are freewares. After

linkage analysis, linked markers are grouped together into linkage groups, each of which

represents an entire chromosome in most cases. An important use of the linkage map is to

identify the chromosomal regions containing QTLs associated with traits of interest in a

QTL analysis. Such linkage maps with QTL positions marked on them could be referred to

as QTL maps.

Sex-specific linkage maps were constructed for all the shrimp species, as

recombination rates are different between sexes. Because, the choice of appropriate

mapping function (either Kosambi or Haldane) depends on the recombination frequency.


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Salmonid fish have the largest reported sex-specific differences in recombination ratios for

any known vertebrate. In some species like Arctic char and Atlantic salmon, females have

higher recombination rates than males whereas in others like Japanese flounder males

have higher recombination rates over females.

15.5. QTL analysis

Single marker analysis, simple interval mapping and composite interval mapping are the

three methods widely used for QTL detection. Family structure of the mapping population,

i.e. number of families and family size; and also the heterozygosity of the QTL have a

major impact on the power of QTL detection. The power of QTL detection is affected

more by increasing the number of the progeny than by increasing the number of families.

The QTL identified could be (1) a functional mutation itself or (2) a marker that is in

population-wide linkage disequilibrium with functional mutation or (3) a marker that is in

population-wide linkage equilibrium with the functional mutation. Application of Marker

Assisted Selection (MAS) for genetic improvement varies with each of these three cases,

first case being the easier and straight-forward to apply. The second and third cases should

lead to the identification of functional mutation responsible for phenotype. Markers

identified should be validated for their reliability in predicting the phenotype in different

populations. Validation is necessary because false-associations between markers and the

trait of interest can arise.

15.6. Parentage assignment

Microsatellites are highly polymorphic markers with tens of alleles at each locus. These

highly polymorphic microsatellites were thoroughly studied to develop marker panels for

application in parentage assignment of progeny in selection programs. This allows

breeders to go in for communal rearing of families of progeny and obviates the need for

adjustment of various effects leading to unbiased estimates of genetic parameters.

15.7. Association studies

So far, very few species genome is fully sequenced and marker database at genome level

is not available. This limits the application of genome-wide association studies. Therefore

candidate gene approaches, wherein markers in selected candidate genes for economic

traits are tested for association, have been applied. Microsatellites and SNP markers were

explored for their association to growth, disease resistance, cold tolerance, meristic traits,

stress response etc. Many association studies focused on growth due to its direct


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importance to pricing of produce and easy recording of phenotype. If these association

studies are part of on-going genetic improvement programs, then the associated loci could

be incorporated into programme through MAS.

15.8. Population studies

The natural habitats of most of aquatic species spans across large volumes of waters and

several stocks are defined based on geographical locations with no importance to genetic

similarities. It is customary to know the genetic-relatedness across stocks for conservation

and also for choosing the best possible base population for breeding programs.

Microsatellite markers were applied for assessing population structure of different

aquaculture species in their natural geographic populations, assessing genetic variability in

breeding populations and to study changes in genetic diversity during domestication

process.

15.9. Species identification

Species identification assumes special importance in aquaculture sector for two important

reasons, correct identification of species that morphologically appear similar and control

of adulteration. Methodologies were designed for species identification using AFLP and

RFLP markers.

15.10. Bioprospecting of genetic resources

Aquatic organisms that habitat in extreme conditions of environment such as pressure,

temperature and salinity are the rich source of genetic information. Contributions from

deep sea ecosystems towards bioprospecting of the genetic resources hold a promise of

untapped products, useful to the future of human well-being. The genetic make-up of these

organisms is drawing vast interest for research and potential bioprospecting for

commercial exploitation for pharmaceutical or industrial applications. Sponges in

particular are targeted as potential sources of pharmaceutical products (Table 1).


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Table 1. Bioactive compounds isolated from marine organisms

Product Organism Property

Topsentin Spongosorites ruetzleri Anti-inflammatory and anti-

tumour

Dercitin Dercitus sp Antitumor agent

Strongylin Strongylophora

hartmani

Antiviral activity against the

PR-8 influenza virus

Discodermolide Discodermia dissoluta Anti-tumor activity against

human lung cancer cells and

breast cancer cells

Petrosin Petrosia sp Anti-HIV activity

Halicyclamine A Haliclona sp Anti-tuberculosis agent

US patent: 20020168416 A1 Perna viridis Anti-HIV activity

CadalminTM Gme Perna viridis Arthritis/inflammatory

diseases

Ecteinascidin Ecteinascidia turbinate Anti-cancer agent

15.11. Nutrigenomics

Nutritional genomics is a systems approach in understanding the relationship between diet

and health ensuring the benefits from the genomic revolution. Nutrigenomics in simple

terms is the molecular study associated between nutrition and the response of genes. It can

be defined as the study of the effects of foods and food constituents on gene expression.

Basically, nutrigenomics involves study of the effect of nutrients on the genome,

proteome, and metabolome of an organism to understand the relationship between

nutrition and health using high-throughput genomic tools in nutrition research. In nutrition

research, gene expression profiling therefore may be used for three distinct purposes, 1)

To assist in the identification and characterization of basic molecular pathways that may

be impacted, either positively or negatively, by nutrients, 2) To provide insights upon

specific mechanisms that trigger such beneficial or negative effects and 3) To identify

http://en.wikipedia.org/wiki/Food


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specific genes altered by nutrients that might prove valuable as molecular biomarkers or

nutrient sensors and in gene discovery.

15.12. RNA interference

RNAi technology shows considerable promise as a therapeutic approach and efficient

strategy for shrimp virus control in the aquaculture industry. Progress in understanding the

mechanism of siRNAs at the molecular level, as well as strategies to achieve their tightly

regulated, stable, prolonged and tissue-specific expression in an effective manner, will

definitely revolutionize therapeutic approaches for counteracting viral diseases of shrimp.

Recent studies indicate possible uses of dsRNA for effectively blocking viral disease

progression in shrimp against at least three unrelated viruses: WSSV, Taura syndrome

virus (TSV) and Yellow head virus (YHV).


168

Policies and Guidelines for

Sustainable Coastal Aquaculture

M. Jayanthi and M. Kumaran


16.1. Introduction

Shrimp farming has grown rapidly in recent years in many tropical and subtropical

countries, but there have been setbacks resulting from diseases and the growing awareness

on the environmental and social impacts of shrimp farming. At the global level, rapid

expansion of coastal aquaculture has resulted in large-scale removal of valuable coastal

wetlands and subsequent loss of goods and services generated by natural resource systems.

In India, aquaculture has transformed from a traditional to a commercial activity in the last

two and half decades and the area under shrimp culture has increased from 65,100 to

1,21,600 ha between 1990 and 2015 (MPEDA, 2015). The rapid development of shrimp

aquaculture in the coastal areas of the country also raised some environmental concerns,

and the need for regulatory mechanism to control the indiscriminate growth of aquaculture

was realized.

16.2. Review of legislations and policies of coastal areas in relation to aquaculture

The Indian coastal zone is governed by several official legislations that regulate

development activities including construction, industrial activity and coastal infrastructure.

Some of these legislations have an explicit mandate to protect the coastal ecology and

available natural resources of the region.

During the early phase of British rule in India, there was no state policy for

improving the utilization of natural agricultural resources or any form of welfare

orientation. After independence, as per the Indian Constitution, the state legislatures had

the power to make laws and regulations with respect to a number of subject-matters,

including water (i.e., water supplies, irrigation and canals, drainage and embankments,

water storage and water power), land (i.e., rights in or over land, land tenure, transfer and

alienation of agricultural land), fisheries, as well as the preservation, protection and

improvement of stock and the prevention of animal disease. At the central level, several

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key laws and regulations may be relevant to aquaculture. They include the century-old

Indian Fisheries Act (1897), which penalizes killing of fish by poisoning water and by

using explosives, and the Environment (Protection) Act (1986), being an umbrella act

containing provisions for all environment related issues. They also include the Water

(Prevention and Control of Pollution) Act (1974) and the Wild Life Protection Act (1972).

All this legislation must be read in conjunction with one another to gain a full picture of

the rules that are applicable to aquaculture. The state governments also enacted laws for

regulation of fishing in their respective territorial waters. However, there were no

comprehensive policy guidelines to promote or regulate the coastal and brackishwater

aquaculture at Central or State level, till the enactment of Coastal Regulation Zone (CRZ)

Notification, 1991. Under the prohibited activities, setting up the hatchery and fish drying

unit is exempted. The coast is classified in to four zones namely CRZ I, II, III and IV.

Category I (CRZ-I) covers areas that are ecologically sensitive and important,

such as national parks/marine parks, sanctuaries, reserve forests, wildlife habitats,

mangroves, corals/coral reefs, areas close to breeding and spawning grounds of fish and

other marine life, areas of outstanding natural beauty/historical/heritage areas, areas rich in

genetic-diversity, areas likely to be inundated due to rise in sea level consequent upon

global warming and such other areas as may be declared by the Central Government or the

concerned authorities at the State/Union Territory level from time to time and (ii) Area

between the Low Tide Line and the High Tide Line.

Category II (CRZ-II) includes the areas that have already been developed up to or

close to the shoreline. For this purpose, "developed area" is referred to as that area within

the municipal limits or in other legally designated urban areas which is already

substantially built up and which has been provided with drainage and approach roads and

other infrastructural facilities, such as water supply and sewerage mains.

Category III (CRZ-III) includes areas that are relatively undisturbed and those

which do not belong to either Category I or II. These will include coastal zone in the rural

areas (developed and undeveloped) and also areas within Municipal limits or in other

legally designated urban areas which are not substantially built up.

Category IV (CRZ-IV) includes coastal stretches in the Andaman and Nicobar,

Lakshadweep and small islands except those designated as CRZ-I, CRZ-II or CRZ-III.


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A rational policy to combine environmental and economic developments for

regulating the sustainable shrimp farming has been a difficult goal to achieve in view of

potentially conflicting interests and lack of an integrated vision of coastal phenomena. The

first legal initiation specifically taken for regulating the shrimp farming in the country was

by the state government of Tamil Nadu with the enactment of the Aquaculture Regulation

Act in 1995. However, this Act complicated the issues further because of the bureaucracy

in (i) issuing licenses, (ii) certification and leasing of land, (iii) permission for the

utilization of ground water etc.

As the matter was taken to the Supreme Court, it ordered in its 11th

December 1996

verdict, that demolition of all aqua farms falling within the 500 metre from the baseline in

the Coastal Regulation Zone (CRZ) by 31 March 1997, which was further extended up to

30th

April. However, the Ministry‟s guidelines allowed a new slab system exempting about

60% of the aqua farms, which were falling under the traditional culture system, from the

purview of the court order.

The Honourable Supreme Court in its orders on the Writ Petition (Civil) No. 561

of 1994 dated 11.12.96 directed the Central Government to constitute the authority before

January 15, 1997 and stated in the verdict, “The Central Government shall constitute an

authority under Section 3(3) of the Environment (Protection) Act, 1986 and shall confer

on the said authority all the powers necessary to protect the ecologically fragile coastal

areas, sea shore, water front and other coastal areas and specially to deal with the situation

created by the shrimp culture industry in the coastal States, Union Territories”.

Following the directions of the Honourable Supreme Court, Government of India

issued Gazette notification (No. 76 dt. 6.2.1997) regarding the constitution of the

Aquaculture Authority of India. Subsequently, THE AQUACULTURE AUTHORITY

BILL, 1997 (Bill No. XVII-C of 1997) was presented in the Parliament and it was passed

by the Rajya Sabha on 20th March, 1997.

16.3. Coastal Aquaculture Authority Act (2005)

Under the Coastal Zone Notification Regulation 1991 controls are applicable to coastal

stretches of seas, bays, estuaries, creeks, rivers and backwaters which are influenced by

tidal action. The intertidal area along with a 500 m zone from the high tide line is

identified as a zone where development is restricted or prohibited, though exemptions are

granted for permitted activities which require waterfront or seafront access. Amongst


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permitted activities, hatcheries were included but aquaculture was omitted, and it was,

therefore, necessary to determine the status of aquaculture under the Regulation by legal

proceedings. The Aquaculture Authority has brought out guidelines for the development

of sustainable aquaculture. Coastal Aquaculture Authority Act was enacted in 2005 and a

new Coastal Aquaculture Authority was instituted as per the Gazette Notification No.

1336 dated 22nd December 2005. The Aquaculture Authority constituted under the

directives of the Supreme Court laid down certain conditions, related to the nature and

conversion of the land used for shrimp farming, banning intensive and semi-intensive

farming systems, requirement of Effluent Treatment Ponds and EIA etc., for issuing

approval (licence) for the shrimp farms. State level and District level committees were

constituted by the State Governments for screening the applications on the basis of the

above guidelines for recommendation to the Aquaculture Authority for issue of licence.

Coastal Aquaculture Act, 2005 has inserted a sub-paragraph “nothing contained in

this paragraph shall apply to coastal aquaculture of CRZ Notification of 1991”, which

makes the Coastal Aquaculture a permissible activity in CRZ.

A stipulation is included in this Bill that no licence for aquaculture should be

granted allowing aquaculture within 200 metre of the high tide line or any area within the

coastal regulation zone. However, this is subject to the provision that it does not apply to

any aquaculture farm in existence at the time of the establishment of the Aquaculture

Authority.

Accordingly, the Coastal Aquaculture Authority Act 2005 has come into practice,

which encompasses the farming of shrimp, prawn, fish or any other aquatic life under

controlled conditions in ponds, pens enclosures or any other brackishwater bodies

(excluding freshwater aquaculture). Under this Act, coastal area for aquaculture includes

the land within a distance of two kilometers from the High Tide Line of seas, rivers,

creeks and backwaters.

As per the Notification dated 23 January 2006, i) the delineating boundaries for

coastal aquaculture along rivers, creeks and backwaters shall be governed by the distance

unto which the tidal effects are experienced and where salinity concentration is not less

than 5 ppt and ii) In the case of ecologically fragile areas, such as Chilka Lake and Pulicat

Lake, the distance would be up to 2 km from the boundary of the lakes.


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16.3.1. Functions of the Coastal Aquaculture Authority (CAA)

The functions of CAA includes,

ensure that the agricultural lands, salt pan lands, mangroves, wet lands, forest

lands, land for village common purposes and the land meant for public purposes

and national parks and sanctuaries shall not be converted for construction of

coastal aquaculture farms so as to protect the livelihood of coastal community;

deal with any issues pertaining to coastal aquaculture including those which may

be referred to it by the Central Government;

survey the entire coastal area of the country and advise the Central Government

and the State / Union Territory Governments to formulate suitable strategies for

achieving eco-friendly coastal aquaculture development;

advise and extend support to the State / Union Territory Governments to construct

common infrastructure viz., common water in-take and discharge canals by the

coastal aquaculture farms and common effluent treatment systems for achieving

eco-friendly and sustainable development of coastal aquaculture;

fix standards for all coastal aquaculture inputs viz., seed, feed, growth supplements

and chemicals / medicines for the maintenance of the water bodies and the

organisms reared therein and other aquatic life;

collection and dissemination of data and other scientific and socio-economic

information in respect of matters related to coastal aquaculture;

direct the owners of the farm to carry out such modifications to minimise the

impacts on coastal environment including stocking density, residual levels / use of

antibiotics, chemicals and other pharmacologically active compounds.

order seasonal closure of farms for ensuring sustainability of the coastal

aquaculture practices;

order closure of coastal aquaculture farm in the interest of maintaining

environmental sustainability and protection of livelihoods or for any other reasons

considered necessary in the interest of coastal environment.

make suitable recommendations to the Government for amending the guidelines

from time to time taking into account the changes in technology, farming practices,

etc., and incorporating such modifications in the guidelines to ensure

environmental protection and the livelihoods of the coastal communities


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16.3.2. Guidelines for site selection of aquaculture

• Mangroves, agricultural lands, saltpan lands, ecologically sensitive areas like

sanctuaries, marine parks, etc., should not be used for shrimp farming.

• Shrimp farms should be located at least 100 m away from any human settlement in

a village/ hamlet of less than 500 population and beyond 300m from any village/

hamlet of over 500 population. For major towns and heritage areas it should be

around 2 km.

• All shrimp farms should maintain 100 m distance from the nearest drinking water

sources.

• The shrimp farms should not be located across natural drainage canals/ flood drain.

• While using common property resources like creeks, canals, sea etc., care should

be taken that the farming activity does not interfere with any other traditional

activity such as fishing etc.

• Spacing between adjacent shrimp farms may be location specific. In smaller farms,

at least 20 m distance between two adjacent farms should be maintained,

particularly for allowing easy public access to the fish landing centers and other

common facilities. Depending upon the size of the farms, a maximum of 100–150

m between two farms could be fixed. In case of better soil texture, the buffer zone

for the estuarine based farms could be 20–5 m. A gap having a width of 20 m for

every 500 m distance in the case of sea based farms and a gap of 5 m width for

every 300 m distance in the case of estuarine based farms could be provided for

easy access.

• Larger farms should be set up in clusters with free access provided in between

clusters.

• A minimum distance of 50–100 metre shall be maintained between the nearest

agricultural land (depending upon the soil condition), canal or any other water

discharge/ drainage source and the shrimp farm.

• Water spread area of a farm shall not exceed 60 per cent of the total area of the

land. The rest 40% could be used appropriately for other purposes. Plantation

could be done wherever possible.


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• Areas where already a large number of shrimp farms are located should be

avoided. Fresh farms in such areas can be permitted only after studying the

carrying/ assimilation capacity of the receiving water body.

16.3.3. Shrimp farm registration and renewal

(1) All persons carrying out aquaculture in the coastal areas shall register their

farm with the CAA. Such registration made for a period of five years with facility for

further renewal. Aquaculture will not be permitted within 200 m from HTL and also in

creeks, rivers and backwaters within the CRZ. However it is not applicable to the existing

farms set up before CAA act 2005 and to the non-commercial and experimental

aquaculture farms operated by any research institute of the Government or by the

Government. Every application for the registration of a coastal aquaculture farm shall be

made to the District Level Committee as set up by the Authority in Form I, obtainable

from the office of the District Level Committee or the office of the Authority or be

downloaded from the website of the Authority.

(2) Every application for the registration of coastal aquaculture farm specified in

column (1) of the Table below shall be accompanied by the fee specified in the

corresponding entry in column (2) of the said Table.

(3) The fees for registration shall be payable in the form of Demand Draft in favour

of the Member Convener of the District Level Committee set up by the Authority.

(1) (2)

1. Up to 5.0 hectare (ha)

water spread area

Rs.200/- per ha (or fraction of a ha),

subject to a minimum of Rs.500/-.

2. From 5.1 to 10 ha water

spread area

Rs.1000/- plus Rs.500/- per ha (or fraction

of a ha) in excess of 5 ha.

3. From 10.1 ha water

spread area and above

Rs.3500/- plus Rs.1000/- per ha (or

fraction and above of a ha) in excess of 10

ha.


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On receipt of an application the District Level Committee shall verify the

particulars given in the application in respect of all coastal aquaculture farms irrespective

of their size; and

(a) in the case of coastal aquaculture farms up to 2.0 ha water spread area, the

District Level Committee upon satisfaction of the information furnished therein shall

recommend the application directly to the Authority for consideration of registration under

intimation to the State Level Committee.

(b) in the case of coastal aquaculture farms above 2.0 ha water spread area, the

District Level Committee shall inspect the concerned farm to ensure that the farm meets

the norms specified in the guidelines with specific reference to the siting of coastal

aquaculture farms and recommend such applications to the State Level Committee, which

upon satisfaction shall further recommend the application to the Authority for

consideration of registration.

The time frame of four weeks to the DLC for the detailed inspection and dispatching

to SLC and two weeks for the SLC to give the recommendations are prescribed.

16.4. Introduction of Pacific white shrimp (Litopenaeus vannamei)

The declined trend in shrimp aquaculture production and its export to other countries in

recent years have created an alarming situation in the aquaculture industry. This created an

opportunity for the farmers to think and search for an alternative disease free or specific

pathogen free species to revive the industry. After careful risk analysis study and trial

culture, the Government of India permitted the farmers to import an exotic shrimp SPF

(Specific Pathogen Free) Litopenaeus vannamei for its seed production and farming in the

country to safeguard the shrimp industry and increase production. However, before

introduction Government of India through Ministry of Agriculture has notified

[S.O.2482(E)] the guidelines for operation of aquatic quarantine facilities for the import of

SPF L. vannamei under the livestock importation Act,1898 (as amended in 2001) on 15th

October 2008. Subsequently, Ministry has also issued notification [G.S.R. 302(E)] on the

Guidelines for regulating hatcheries and farms involved in L. vannamei seed production

and culture on 30th

April 2009.

As per the guidelines, the Department of Animal Husbandry, Dairying and

Fisheries, Ministry of Agriculture has authorized CAA to grant permission to hatcheries

for importing broodstock of SPF L.vannamei from selected suppliers. An Aquatic


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Quarantine Facility has been set up for this purpose at Neelankarai, Chennai. Hatchery

owners indenting to import broodstock and produce seed of SPF L. vannamei are required

to apply in the prescribed format to CAA.

The CAA has also been authorized to grant permission for farming SPF L.

vannamei to eligible shrimp farmers as per the guidelines issued by the Department of

Animal Husbandry, Dairying and Fisheries. Farmers fulfilling the mandatory biosecurity

requirements for this culture, viz. fencing of farms, provision of reservoirs for water

intake; bird scares/ bird netting, crab fencing and Effluent Treatment System (ETS) may

apply to CAA in the prescribed format for farming SPF L. vannamei. Permission shall be

granted by CAA after physical verification by the Inspection Team regarding the

availability of such facilities.

16.4.1. Guidelines for regulating Aquatic quarantine operations for import of SPF L.

vannamei

16.4.1.1. Import permit and port of entry

• Permission for importing the broodstock of L. vannamei shall be granted by the

Coastal Aquaculture Authority (CAA) according to the annual requirement of SPF

L. vannamei broodstock to the eligible applicants.

• The CAA in consultation with National Fisheries Development Board (NFDB),

Central Institute of Brackishwater Aquaculture (CIBA) and Marine Products

Export Development Authority (MPEDA) shall short-list the SPF L. vannamei

suppliers based on the genetic base and disease status. Import of SPF broodstock

shall be permitted only from such suppliers.

• Chennai shall be the designated port of entry for the import of SPF broodstock.

• SPF L. vannamei broodstock shall be imported into India only with a valid sanitary

import permit issued under clause (3).

• All applications for a permit to import consignments by land, air or sea shall be

made in either Form A or Form B, whichever is relevant, and sent in triplicate to

the Joint Secretary, Trade Division, Department of Animal Husbandry and

Dairying, Ministry of Agriculture, Government of India.

• The sanitary import permit shall be issued by the Central Government in exercise

of the powers conferred by Section 3A of the Live-stock Importation Act, 1898 (9

of 1898). The import permit issued under this clause shall be valid for a period of


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six months, but can be extended by the concerned authority for a further period of

six months, on request from the importer and for reasons to be recorded in writing.

16.4.1.2. Pre-border quarantine requirement

The following certificates in original, issued by the competent authority of the exporting

country should accompany the consignment of SPF broodstock and copies of the

certificates should be made available to the quarantine officer at least 2 days before arrival

of the consignment.

A certificate indicating the SPF status of the broodstock in relation to the

pathogens excluded in the shrimps.

A certificate indicating the history of disease occurrence in the broodstock rearing

facility of the exporter for the last two years.

A certificate indicating that the batch of exported broodstock was held in pre-

quarantine for a period of 12 days and the results of the tests for the following

pathogens should be included.

i) Taura syndrome virus (TSV) (OIE listed)

ii) Yellow head virus (YHV) (OIE listed)

iii) Infectious myonecrosis virus (IMNV) (OIE listed)

iv) Infectious hypodermal and haematopoietic necrosis virus (IHHNV) (OIE

listed)

v) Baculovirus penaei (BP) (OIE listed)

vi) White spot syndrome virus (WSSV) (OIE listed)

vii) Necrotising hepatopancreatitis bacterium α-Proteobacterium (NHPB)

• The testing should have been done not earlier than 10 days before the actual

shipment.

• Before shipment, detailed information on the actual quantity/ number of

broodstock to be imported should be furnished in the form of package slip

indicating the number of cartons they are packed in.

16.4.1.3. Quarantine requirements

• The importers should book their space in the quarantine facility well in advance by

providing copies of the relevant documents to the Animal Quarantine Officer and

paying the requisite fees as may be fixed by the Ministry of Agriculture

(Department of Animal Husbandry, Dairying & Fisheries).


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• Clearance of the consignment of SPF brood stock at the airport, its transportation

to quarantine facility along with the quarantine staff, maintenance at the quarantine

facility and repacking and transportation to the hatcheries shall be the

responsibility of the importer.

• The packing materials should be of good quality in order to avoid any accidental

damage.

• The space in the carton should comply with acceptable densities specified for L.

vannamei.

• The consignment should not be opened at any transit point. If it is found to be

tampered, the entire consignment shall be rejected and the animals will be

destroyed.

• The importer shall receive the consignment only at Chennai.

• Precautions should be taken to prevent spillage of water and damage to the

containers during transportation.

• In the event of any accidental spillage of water during transport, the importer shall

ensure the decontamination of water using OIE approved disinfecting procedures.

• There shall be a gross inspection of the consignment on arrival by the Animal

Quarantine Officer but before its despatch to the quarantine facility. The

quarantine staff may accompany the consignment till it reaches the quarantine site

and the consignment will be opened at the specified site in the presence of the

representatives from Coastal Aquaculture Authority (CAA) and Central Institute of

Brackishwater Aquaculture (CIBA) to ensure that the supply has been received in

good condition and as per the terms and conditions of the permission for import of'

L. vannamei.

• The samples from the imported shrimp should be collected before releasing them

into the tanks at the quarantine facility.

• The vehicles used for transport of the exotic brood stock from the airport to the

quarantine facility shall be disinfected immediately after the transfer of the animals

to the quarantine and the containers used for the transport should be destroyed

under supervision of the team as may be designated by the CAA.

• A minimum quarantine period of five days in case of shrimp brood stock shall be

observed to ensure that the consignment is free of diseases and poses no risk.


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• The brooders in the quarantine will be tested by CIBA for all known pathogens

through OIE prescribed methodologies. The health of the brooders shall be

monitored everyday and the visual changes recorded in a register. Mortality, if any,

shall be recorded in a separate register. The moribund or visibly weak animal shall

be preserved in ethanol and formalin for further disease investigations.

• No live feed shall be given to the brooders during the quarantine period. Only

pelleted feed of standard companies shall be used for feeding after check for any

pathogen. The leftovers and metabolic wastes should be removed immediately, as

per the quarantine procedures.

• Disinfectant bath of 1:2000 KMnO4 should be maintained in the quarantine facility

and all persons entering or leaving should wash their hands and feet in the bath.

• During the initial five days period of quarantine, if any exotic disease is observed

the entire brood stock should be destroyed.

• The infected stock or dead animals if any should be destroyed in an appropriate

incinerator.

• After clearance from the quarantine, the imported brood stock shall be handed over

to the importer.

• After dispatch of the batch of brood stock from the quarantine, the equipment used

should be disinfected with 200 ppm free chlorine overnight and the building or the

quarantine space should be disinfected with 17.5 g potassium permanganate and 35

mL of 37% aqueous formalin per 100 cubic feet area.

• All waste waters released from the quarantine should be disinfected with chlorine

and then de-chlorinated before release. The Effluent Treatment System (ETS)

should be designed to handle the total water volume used in the quarantine.

16.4.2. Guidelines for regulating hatchery operations of SPF L. vannamei and P.

monodon

16.4.2.1. Criteria for application to breed SPF L. vannamei and P. monodon

(1) Hatcheries engaged or intending to be engaged in shrimp seed production

having the required bio-security facilities as prescribed by Coastal Aquaculture Authority

would be eligible to apply for registration under the Coastal Aquaculture Authority Act,

2005 and the Rules framed there under and for permission to import SPF broodstock and

to produce and sell post larvae.


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(2) Approval of the hatchery for rearing L. vannamei/ P. monodon will be given by

Coastal Aquaculture Authority after due inspection of the hatchery facilities by a team

constituted by Coastal Aquaculture Authority for this purpose.

(3) The hatchery facilities should have strict bio-security control through physical

separation or isolation of the different production facilities which is a feature of good

hatchery design. In existing hatcheries with no physical separation, effective isolation may

also be achieved through the construction of barriers and implementation of process and

product flow controls.

(4) The hatchery facility should have a wall or fence around the periphery of the

premises, with adequate height to prevent the entry of animals and unauthorized persons.

This will help to reduce the risk of pathogen introduction by this route, as well as improve

overall security.

16.4.2.2. Sanitary requirement

(1) Entrance to the hatchery should be restricted to the personnel assigned to work

exclusively in this area and a record of personnel entering the facility should be

maintained by the security personnel.

(2) Hatchery staff should enter through a shower or dressing room, where they

remove their street clothes and take a shower before entering another dressing room to put

on working clothes and boots. At the end of the working shift, the sequence should be

reversed.

(3) There should be means provided for disinfection of vehicle tyres (tyre baths at

the gate), feet (footbaths containing hypochlorite solution at > 50 ppm active ingredient),

and hands {bottles containing iodine-PVP (20 ppm and/or 70% alcohol)} to be used upon

entering and exiting the unit.

16.4.2.3. Water intake

(1) Each functional unit of the hatchery should have independent water treatment

facility and it should be isolated from all other water supply systems. Separate

recirculation systems may be used for each functional unit of hatchery to reduce water

usage and improve bio-security, especially in high-risk areas.

(2) Water for the hatchery should be filtered and treated to prevent the entry of

vectors and pathogens that may be present in the source water. This may be achieved by


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initial filtering through sub-sand well points, sand filters (gravity or pressure), or mesh bag

filters into the first reservoir or settling tank. Following primary disinfection by

chlorination, and after settlement, the water should be filtered again with a finer filter and

then disinfected using ultraviolet light (UV) and/or ozone.

(3) The water supply system may include use of activated carbon filters, the

addition of ethylene diamine tetra acetic acid (EDTA) and temperature and salinity

regulation.

16.4.2.4. Water treatment and discharge of waste water

(1) The discharged water from the hatchery should be held temporarily and treated

with hypochlorite solution (> 20 ppm active chlorine for not less than 60 min) or other

effective disinfectant prior to discharge. This is particularly crucial where the water is to

be discharged to the same location as the abstraction point.

(2) The seawater to be used in the facility must be delivered into a storage tank

where it will be treated with hypochlorite solution (20 ppm active ingredient for not less

than 30 min) followed by sodium thiosulphate (1 ppm for every ppm of residual chlorine)

and strong aeration.

(3) No waste water shall be released out of the hatchery without chlorination and

dechlorination, especially to prevent the escape of the larvae into the natural waters.

Effluent Treatment System (ETS) should be designed to include this provision.

16.4.2.5. Disinfection of implements

(1) Used containers and hoses must be washed and disinfected with hypochlorite

solution (20 ppm) before further use.

(2) Each brood stock holding tank should have a separate set of implements which

must be clearly marked and placed near the tanks. Facilities for disinfection of all the

implements at the end of each day‟s use should be available.

16.4.2.6. Broodstock in hatchery

(1) Only SPF brood stock cleared through the quarantine should be used in the

hatchery for seed production.

(2) Use of pond-reared brood stock is strictly prohibited.


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(3) Hatcheries involved seed production should not use any other species within

the hatchery premises.

16.4.2.7. Seed production and sale

(1) Nauplii should not be sold to other hatcheries. Only tested and certified post

larvae should be sold.

(2) Post larvae should be sold only to the farmers who have registered with the

Coastal Aquaculture Authority. A copy of the Certificate of Registration issued by Costal

Aquaculture Authority should be retained by the hatchery operator for inspection.

(3) Detailed record of the seed production as well as sale including the name and

address of the buyer or farmer should be maintained.

16.4.2.8. Disease reporting and record maintenance

(1) Any disease outbreak in the hatchery should be reported immediately to Costal

Aquaculture Authority.

(2) The hatcheries should maintain a record of the imported broodstock with

details of source, quantity imported, the number of mortality, eggs produced, nauplii

produced, post larvae produced, post larvae sold, name and address of the farmer to whom

sold, date and number of the registration and permission certificate issued by Costal

Aquaculture Authority and should report these in their quarterly compliance reports to be

submitted to Coastal Aquaculture Authority as per the format.

16.4.2.9. Inspection

Coastal Aquaculture Authority authorized personnel shall visit periodically to check the

status of the broodstock, the seed production and sale.

16.4.2.10. Bank Guarantee

The approved hatcheries will deposit a bank guarantee for rupees five lakh in favour of the

Costal Aquaculture Authority to ensure compliance of the guidelines by them and in the

event of any violation the Bank Guarantee shall be invoked.


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16.4.3. Regulations for SPF L. vannamei farms

16.4.3.1. Eligibility criteria for farms

(1) Aquaculture farmers who are registered with Coastal Aquaculture Authority

will be required to submit a separate application for permission for farming L. vannamei.

In case of so far unregistered farms, the application for registration must clearly spell out

the intention to culture L. vannamei. Decision on such applications will be taken in

accordance with these guidelines.

(2) Inspection team authorized by Coastal Aquaculture Authority shall inspect the

farm and based on its recommendation regarding the suitability of the facility for farming

of L. vannamei, applications shall be processed by the Member Secretary for consideration

of the Coastal Aquaculture Authority for issuing permission to farms for farming of L.

vannamei.

(3) Farms must establish adequate bio-security measures including fencing,

reservoirs, bird-scare, separate implements for each of the ponds etc. The farms should be

managed by the personnel who are trained and/or experienced in management of bio-

security measures.

(4) L. vannamei shrimp is tolerant to low salinities but the rearing water should

have a salinity of more than 0.5 ppt. The Govt. of India has notified that farmers who

desired to culture vannamei outside the jurisdiction of CAA having the water salinity of

above 0.5 ppt shall get registered with the Department of Fisheries (DoF) of the state

government concerned. The farms should possess all the required infrastructure and

biosecurity. The DoF may constitute a separate district level committee to inspect and give

registration to the farms within a reasonable time frame of 60 days and other guidelines

are same as that of brackishwater area.

(5) Farms irrespective of their size should have an Effluent Treatment System

(ETS). Since loading of the environment with suspended solids is very high during the

harvest, the ETS should be able to handle the waste water let off during harvest.

Harvesting should be sequential depending on the size of the ETS. The quality of the

waste water should conform to the Standards prescribed under the Guidelines issued by

Coastal Aquaculture Authority.


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16.4.3.2. Water discharge protocols

(1) In case of any outbreak of disease, distress harvesting is permitted through

netting only and the water should be chlorinated and de-chlorinated before release into

drainage system.

(2) Waste water should be retained in the ETS for a minimum period of two days.

(3) Farms which follow Zero Water Exchange system of farming will also be

encouraged to take up L. vannamei farming.

16.4.3.3. Bio-security considerations

(1) It is advisable not to culture SPF L. vannamei if the neighbouring farms are

culturing native species, which are non-SPF, since L. vannamei is susceptible for all the

viral pathogens reported in Penaeus monodon in India.

(2) Farms approved for L. vannamei culture would not be permitted for farming of

any other crustacean species.

16.4.3.4. Norms for culture of L. vannamei

(1) Tested and certified seed should be procured only from hatcheries authorized

for import of the vannamei brood stock and/or production of vannamei seed.

(2) Stocking densities should not exceed 60 nos./m2.

(3) Strict compliance for the waste water standards is a mandatory requirement

and Inspection team authorized by Coastal Aquaculture Authority in each case shall

monitor the quality of waste water as per the procedures laid down in the Regulations

under Coastal Aquaculture Authority Act, 2005.

16.4.3.5. Record maintenance at farms

(1) The farmers should maintain a detailed record of the name and address of the

hatchery from where they procured the seed, quantity procured, number and date of the

valid registration of the hatchery.

(2) The farmers should record the quantity of shrimp produced, sold, and the

name and address of the processor to whom sold and this should be reported to the Coastal

Aquaculture Authority through quarterly compliance reports as per the proforma.


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16.4.4. Guidelines for permitting farms which are registered for P. monodon culture

to take up L. vannamei culture

The Govt. of India has amended the guidelines based on the representations from the

farming community who have registered for tiger shrimp (P. monodon) culture to take up

L.vannamei farming and notified the following amendments to the CAA guidelines in the

year 2015.

Maximum stocking density of twenty numbers of post larvae per square metre is

permissible under this type of culture.

The usage of aerator facility shall be restricted and be permitted only during

emergency and/or during the last two months of culture.

Considering the biomass and low input farming maximum of six horse power

aerators per hectare only will be permitted.

Biosecurity requirements are essential irrespective of the size of the farm for

ensuring successful culture.

For farms having an area of more than 2 ha, reservoir ponds are mandatory.

However, for farms having an area of up to 2 ha the need for reservoir pond is left

optional.

To avoid the risk of disease occurrence using non-disinfected creek water while

filling up the ponds, water disinfection prior to stocking should be done in the pond

itself, in case if they do not have the reservoir ponds.

Zero water exchange system should be strictly followed with in-situ

bioremediation with probiotics.

All the other biosecurity requirements like filtration, fencing (men, crab and bird)

and disinfection protocol for the labour and implements should be strictly

followed.

Effluent Treatment System (ETS) is mandatory in P. monodon farms of above five

hectares. In case of L.vannamei culture, ETS is mandatory for all farms

irrespective of the size when they follow the stocking density of up to sixty

numbers per square meter as provided in the Guidelines for L. vannamei culture. In

low density culture of L. vannamei (i.e., 20 nos./m2), ETS is left optional for farms

of less than five hectares as was followed in the case of P. monodon culture.


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Since ETS is optional an account of low stocking density in order to prevent

escapes in to the natural environment the harvesting shall be done only through

drag netting.

After the culture and harvest the water in the pond shall be retained for at least

three days for the settlement of suspended particles and disinfected before release.

Though these guidelines are issued having due regard to the biosecurity protocols

to the benefit of small independent farms, it always advisable to go for group

farming with common reservoirs, common ETS and collective biosecurity

protocols.

To make the process of conversion simpler the registered farms can submit a letter

to the CAA seeking permission for doing low density L. vannamei culture as per

these guidelines along with their registration certificate for endorsement. The

endorsement will be made after suitable inspection to the facility.

Any violation of these guidelines shall result in cancellation of the permission

issued for taking up of SPF L. vannamei culture besides other actions provided

under the CAA Act, 2005 and rules and regulations made there under.

16.5. Conclusion

Sustainable coastal aquaculture hinges on environmental protection and social

responsibility. The guidelines are framed to ensure environment friendly, socially

acceptable and sustainable aquaculture which should not disturb the other production

systems and end users of natural resources. Self-discipline is the secret of sustainability.

Therefore, the shrimp farmers and other stakeholders need to follow the regulatory

guidelines and should integrate themselves with the Coastal Zone Development

programmes so that shrimp farming can be sustained and continue to help in improving

the socio-economic capabilities of the coastal population.


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Contributors

Chapter Authors

1. Site selection, design and construction of

different types of brackishwater aquafarms

Gouranga Biswas, Prem Kumar,

Christina L.

2. Biology of cultivable brackishwater finfishes

and shellfishes

Prem Kumar, Gouranga Biswas,

Krishna Sukumaran, Babita Mandal

3. Breeding and seed production of

brackishwater finfishes

Prem Kumar, Gouranga Biswas, M.

Kailasam, M. Natarajan

4. Sustainable brackishwater fish culture

practices

Gouranga Biswas, Prem Kumar,

S.N. Sethi, Aritra Bera

5. Shrimp farming with special reference to

Litopenaeus vannamei culture

Christina L., P.S. Shyne Anand

6. Soil and water quality management in

brackishwater aquaculture

R. Saraswathy, P. Kumararaja, M.

Muralidhar

7. Nutrition, feed formulation and feed

management in brackishwater aquaculture

T.K. Ghoshal, Debasis De

8. Advances in mud crab farming P.S. Shyne Anand, C.P.

Balasubramanian, Christina L., T.K.

Ghoshal

9. Concept and scope of organic brackishwater

aquafarming

Akshaya Panigrahi, P.S. Shyne

Anand, C.P. Balasubramanian

10. Brackishwater ornamental fish culture Krishna Sukumaran, S.N. Sethi,

Gouranga Biswas, Prem Kumar

11. Biosecurity and best management practices

in shrimp aquaculture

C.P. Balasubramanian, P.S. Shyne

Anand, Akshaya Panigrahi

12. Application of periphyton and biofloc

technologies- New opportunities in

brackishwater farming

P.S. Shyne Anand, C.P.

Balasubramanian, Akshaya

Panigrahi

13. Brackishwater fish and crustacean diseases

and their control

Sanjoy Das, S.K. Otta, M. Makesh,

S.V. Alavandi

14. Fish health management in brackishwater

aquaculture with special reference to

emerging diseases

K.V. Rajendran, Sanjoy Das, P.K.

Patil

15. Application of genetics and biotechnological

tools in aquaculture

M.S. Shekhar, K. Vinaya Kumar

16. Policies and guidelines for sustainable

coastal aquaculture

M. Jayathi, M. Kumaran


188

LIST OF PARTICIPANTS

Sl.

No.

Name Address Contact number/ Email

1. Mr. Sayuj Sudhakaran

Menon (Entrepreneur)

Plot 146, Sector 4,

Gandhidham, Kutch, Gujarat-

370201.

08891000141

[email protected]

2. Ms. Kashmira Rathore

(Entrepreneur)

Flat no. 1, Amrit Appt, Plot 29,

Sector 5, Gandhidham, Kutch,

Gujarat- 370201.

08891000141

3. Mr. Pavel Biswas

(Student)

Subhasgram, Bankplot, M.M.

Bose Road, Kolkata- 700146

09163695321

[email protected]

4. Mr. Soumen Das

(Farmer)

Vill.+P.O.- Abad Kuliadanga,

P.S.- Hasnabad, Distt.- North

24 Parganas, West Bengal,

PIN- 743456

08972753030

[email protected]

5. Ms. Madhurima Sarker

(Student)

Faculty of Fishery Sciences,

WBUAFS, 5, Budherhat Road,

Chakgaria, Kolkata 700094.

[email protected]

6. Ms. Riya Dinda

(Student)




08420181265

[email protected]

7. Mr. Sourav Dhabal

(Student)




[email protected]

8. Ms. Banasree Biswas

(Student)




[email protected]

9. Mr. Saurabh

Chandrakar (Student)




[email protected]

10. Mr. Nirmalya Mondal

(Technical Assistant)




09088444919

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