ISSN 0254-380 X

No. 183

MARINE FISHERIESMARINE FISHERIESMARINE FISHERIESMARINE FISHERIESMARINE FISHERIES

INFORMAINFORMAINFORMAINFORMAINFORMATION SERTION SERTION SERTION SERTION SERVICEVICEVICEVICEVICE

Janauary, February, March 2005

TECHNICAL AND EXTENSION SERIES

CENTRAL MARINE FISHERIES RESEARCH INSTITUTECOCHIN, INDIA

(INDIAN COUNCIL OF AGRICULTURAL RESEARCH)

Mangroves are the most productive eco-systems and considered as national wealth ofmaritime countries. The marine and brackishwater zones between high and low tide levelare the fond homes of a unique environmentwith a heterogeneous assemblage ofbiocoenosis acclimatized to life in a veryinhospitable and un-predictable environment;mainly in the tropical inter-tidal zone spreadingabout 10 million ha. in 30 countries. The floracomprises macro and microphytic communitieswhich exhibit heterogeneity in its distributionin different formative zones. They vary fromhaline grasses, herbs, twines, climbers, shrubsto tall trees and phytoplankton to pheophyton.The ecosystem is evergreen throughout theyear; self sustaining and renewable, if otherwisenot disturbed from external sources. Thenetwork of root system of plants help in bindingthe nutrient laden soil thereby trapping thenutrients drained of from uplands whichotherwise would have found their way into thesea.

The fauna include resident and migrantarboreal, terrestrial, aquatic and semi aquaticspecies. Mangroves serve as breeding, nurseryand feeding grounds for a large number ofterrestrial and aquatic organisms. It alsoprovides protection from predation and refugefor juveniles of many species. Mangroves andestuaries are a migratory path for catadromousand anadromous fishes.

The wetland ecosystems especially “Mangals”are the most productive and diverse in theworld and more than 80% of the marine

catches are directly or indirectly dependent onmangroves and other coastal ecosystems.Traditionally wetlands have been viewed asenvironments associated with disease,difficulty and danger, but ecologists realize thatthese are amazingly productive areas and justwaiting to be tapped.

Present Status of Mangroves in India

In 1960’s the total area of the Indianmangroves was about 6,81,976 ha in which45% occurs in Sundarban in West Bengal and17% in Andaman and Nicobar Islands and therest distributed in maritime states of India. In1983, the recorded total area of Indianmangroves was 3,56,500 ha. Deforestation andoverexploitation of the mangrove resourceshave resulted into the formation of openmarshy land of approximately 100,000 ha. Thecoastal areas like Gulf of Kutch (Gujarat),Mumbai (Maharashtra) and Cochin (Kerala)are the glaring examples of deforestation,reclamation, conversion and pollution due topopulation pressure.

A survey of mangroves has been conductedin the maritime districts of Kerala during 2001-2003. It has been observed that mangrovesSouth of Cochin are in highly degradedcondition both in the case topography/morphology and biodiversity.

Coastal areas of Kerala are thickly populatedand hence encroachments into the mangrovesare rampant, besides overexploitation of forestand aquatic resources. Over and above,reclamation of land for agriculture, aquaculture

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and other construction purposes resulted in thefragmentation and shrinkage of mangroves ofKerala. Approximately 3-5 crore post larvaeof Penaeus indicus and Metapenaeusdobsoni are collected annually from Keralamangroves in addition to fry and fingerlings ofChanos, Etroplus, Lates and Mugil sp., foraquaculture. The seed collection from wildhas adversely affected the brackish watercapture fisheries of Kerala.

The Sundarban mangroves also have beensurveyed. The establishment of villages in theperiphery and dependence of population onmangroves increased many fold compared to1980’s which is attributed to the migration ofpeople towards coastal area for livelihood.Mangrove products especially forest resourcesare indiscriminately exploited and it hasreached almost a point in certain areas wherechances of regeneration of mangrove forestis remote. Extensive deforestation adverselyaffected the productivity by the reduction oflitter fall, and nutrient level in the mangrovesoils and adjacent water bodies.

The over exploitation of fishery resources,especially the seeds of fin fishes and shell fishfor aquaculture have affected the capturefishery resources of coastal area of WetBengal. It has been estimated that to collectone Penaeus monodon post larva, about 24seeds of different stages of other species aredestroyed which has been reflected in the fishlanding from Bay of Bengal.

Since Sundarban is a vast area with more than8 m tidal amplitude commercially importanttrue marine species also enter into themangroves as occasional visitors. Thejuveniles of such species are also destroyed

in the process of seed collection. Altogetherthe extensive anthropogenic activities resultedin the swindling of Sundarban mangroveresources and shrinking of this importantwetland ecosystem.

The Andaman & Nicobar mangrovesconstitute about 17% of the total mangrovesof the country. These coastal ecosystems arefringing mangroves since in most of the places,the island land mass are steep towards the seaand hence areas of submergence andemergence are not extensive as in the caseof Sundarbans. The water level verticallyrises depending upon the tidal intensity andbeyond this level, only dense true terrestrialforest exists. Nevertheless in some areas themangroves are vast where the terrain isgradually slopping with shallow areas. Becauseof the special nature of topography, truemarine species also enter into the mangrovesof Andaman & Nicobar Islands.

Biodiversity of Indian Mangroves

Flora: The macrophytic vegetation of IndianMangroves belong to helophilous halophyteswhich comprises littoral swamp forest andconsidered as true mangrove plants.

Altogether about 153 species including 36 truemangroves and rest mangrove associates wereidentified. Based on the height of vegetationthe forest plants have been classified into threegroups. 1. The widest trunk with the spreadingcrown in species, Sonneratia and Avicenniaand less spreading crown found in the speciesof Bruguiera and Rhizophora which coversthe top canopy of the mangrove forest. 2.Shrubs and small trees represented byAegiceras, Excoecaria and Ceriops. 3. The

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shrubs and ferns such as Acanthus, Aegilotisand Acrostichum. The distribution and densityof these species depends on variations in thesalinity and tidal amplitude. The network of rootsystems help in binding the nutrient laden soil.The rich productivity is due to huge amount oflitter fall in the mangroves. The annual litterfall normally ranges from 10,000- 14,000 Kg./ha and it is estimated that insects consumesabout 20 – 25 % of available leaf tissues.

The Micro algae comprised about 77 specieswhich were dominated by diatoms in whichonly 40 are found to be true mangrovespecies. Although, the species ofMyxophyceae, Chlorophyceae andBacillariophyceae are most frequentlyoccurring in the mangroves, species ofChrysophytes, followed by Chlorophyta andPyrrophytes dominate the flora.

The zooplankton consisted of 75 species, whichinclude larvae/spawn fry of ichthyo fauna.Based on the occurrence and abundance ofzooplankton, the major groups encountered areCopepods, Amphipods, Decapods, Cladoceraand fish larvae. Mysids, Brachyura larvae,Tanaeids are regarded as minor groups.Zooplanktons, which occur in very smallquantity such as Actinarians, Tanaeids,Halobetes, Aplysia and flat fish larvae are alsoobserved in mangrove ecosystem. Thezooplankton biomass and species diversityusually differ sharply between mangroveecosystems according to temperature, salinity,nutrient and phytoplankton distribution. Salinitycontrols the distribution of marine forms ofzooplankton.

Benthic faunal assemblage is an essential toolfor assessing the fishery potential of an area.The common macrobenthic species reported

from mangroves are Ploychaetes,Crustaceans, Nemertines, Actinarians,Molluscs and Gobbieds. Among the groupsdecapods are normally higher which couldtolerate wide variations of salinity since theyare euryhaline organisms. During high tide theyenter the mangroves due to their burrowinghabits and nocturnal behaviours help them tosettle at the benthic area of mangrove. Filterfeeders such as species of gastropods andbivalves are also common in the ecosystems.Polychaetes were the dominant group amongbenthos. The rich benthic fauna supportsfishery in the mangrove ecosystems.

Mangrove ecosystems are favourableenvironments for a number of economicallyimportant species on which the artisanalfishery thrives in the coastal areas. Altogether24 species of fin-fish were recoded fromIndian mangroves, mainly from Andaman &Nicobar Islands. While brackish water speciessuch as Etroplus suratensis, Mugil cephalus,Lates calcarifer and Sillago sihamadominated Kerala mangroves, true marine andmigratory fauna were inhabitants and visitorsof Sunderban and Andaman and NicobarIslands mangroves. The local fishermenusually collect the brackish water fish seedsfrom the mangroves and adjacent areas foraquaculture.

According to the earlier reports theoccurrence and collection of milkfish, Chanoschanos juveniles in India are from April – Julywhereas Liza parsia, tade are abundant fromOctober – February. The fry and fingerlingsof pearl spot, Etroplus suratensis occurthroughout the year with a peak from April –July. The fry and fingerlings of sand whitingSillago sihama are available in good numbersthroughout the year with a maximum

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availability from January – May. The fry andfingerlings of grouper (Epinephelus) and seabreams are available from January – April.The crustacean fishery comprised altogether98 species. The commercially importantspecies were Penaeus monodon, P.indicus,Metaperaus dobsoni and Scylla serrata.Mangroves are prime refuge for burrowing shyanimals such as crabs and shrimps. The areais also a conducive environment for crustaceasince it is a shallow, rich in silt and nutrients.

Altogether 70 species of shell fish wereidentified which comprised edible oysters andclams, Crassostrea madrasensis, Pernaverdis, Villorita cyprinoides are extensivelycollected for consumption and limemanufacturing. The reptilian fauna of Indianmangroves comprised 10 species, whichinclude permanent residents, migrants andoccasional visitors for feeding and breeding.The Amphibia was poorly represented withonly 4 species.

The Avian fauna consisted of 57 speciesincluding residents and migrants. The commonspecies were Phalacrocorax niger (Littlecormorant), Phalacrocorax carbo (Largecormorant), Ardea cinerea (Grey heron),Bubulcus ibis coromandus (Cattle egret),Egretta intermedia (Smaller or median egret),E.garzetta garzetta (Little egret), Nycticorax(Night heron). These species enter themangroves for feeding, breeding and nestingpurposes.

The mammals represented with 30 species andonly a few were permanent residents. Thecommon arboreal species were Pteropusgiganteus giganteus (Indian flying fox)Cyropteurs sphinx sphinx (short nosedfruitbat) Rhinolophus lepidus lepidus (Little

Indian horse shoe bat) and Macaca mulattamulatta (Rhesus macoque). Among theterrestrial forms Cais aureus indicus ( Asiaticjackal) Herpertes palustris (Marshmangoose) and Herpestes auropunctatus(Small Indian mangoose) were common.Pantera tigris tigris (Tiger) was a uniquespecies observed in Sunderban MangroveTiger Reserve area in West Bengal. Trueterrestrial animals were also foundoccasionally in the mangroves. They entermainly for feeding.

The Andaman & Nicobar Island mangrovesare rich in the biodiversity of flora especiallymacrophytic vegetation. True mangrove plantsare dense in the fringe areas, while associates,and true forest plants are abundant beyond thehigh tide level. Since terrestrial forest plantsand woods are available, dependence onmangrove vegetation is less in Andaman. Theichthyyo fauna comprises commerciallyimportant species of fin fish and crustaceasuch as Mugil cephalus, Lates calcarifer,Chanos chanos, Sillago sihama,Epinephelus malabaricus, Penaeusmonodon, P. merguiensis, Scylla serrata etc.In Andaman & Nicobar, natural mangroveponds are utilized for aquacultre withoutaltering the topography, which has been foundto be economically viable units.

It has been observed that the propagation,growth, distribution and population dynamics ofthe mangrove biota largely depended on thevariations of aqua-edaphic parameters,topography and anthropogenic activities. InKerala and West Bengal human interventionsand transformation of topography / morphologyand over exploitation of resources resulted notonly in the shrinking of the mangroves but alsodeteriorated the general environment

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considerably which are evidenced by thedisappearance or rare occurrence of certaincommercially important species of flora andfauna with very law population.

Major Survey / Research Findings

1. The flora of the magroves belong tolittoral swamp forest – under helophiloushalophytes which implies that the forestin general is heterogeneous type withthe following groups.

a) True mangroves b) MangroveAssociates

c) Back mangroves /mangrove bioinvasived) Coastal/Beach flora

e) Parasites / Epiphytes / Mistletoes.2. The fauna is represented bya) Arboreal species b) Avian species

c) Amphibiad) Reptiles e) Mammals f) Aquatic

species.3 All the mangroves are associated with

estuaries and creeks except theAndaman and Nicobar Islands wheremost of them are fringing mangroves.

4. All the mangroves except Kerala haverich forest potential with renewable andregeneration possibilities.

5. All three mangroves can substantiallycontribute towards the capture fisheryresources of Arabian Sea and Bay ofBengal, if fish seed collection andoverexploitation are minimized.

6. The overexploitation of ichthyofaunaespecially the seed collection ofcommercially important species foraquaculture and fish based byproductdevelopment resulted in the dwindling ofnatural recruitment and thereby thecoastal capture fisheries especially

artisanal fishery has been adverselyaffected which has reflected in thesocio economic condition of artisanalfishermen in the south west and northeast coast of India.

7. The coastal population / local peopledepend on these fragile ecosystems fortheir livelihood and for various otherpurposes.

8. The rate of conversion/reclamation ofmangrove land is very high in Kerala forother purposes.

9. In Sunderbans new villages especiallyfishing villages are established anddependence on mangroves haveincreased

10. Despite of the awareness campaign byGovernment Organizations, NGOs,Voluntary Agencies, etc for theconservation and management ofmangroves overexploitation andconversion of land for other purposesare continued.

11. This has destroyed the possibilities of themangroes to regenerate and rejuvenatein certain parts of the country besidesthe opportunities for artificial restorationby Participatory afforestation.

12. All the mangroves studied are dumpingplaces directly or indirectly or act assink for pollutants.

13. To sum up, exploitation of mangroveresources and dependence on this wetland ecosystems are at an alarming ratein India.

14. Among the three mangrovesinvestigated Sundarbans in West Bengalis the single largest mangrove in theWorld with the following uniquecharacters:

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Crassostrea sp.

P. monodon

Charybdis cruciata

Some common flora and fauna of mangroves

Acanthus ilicifoliosus Acrostichum aureum

Rhizophora nueronata

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i. Highest biodiversityii. Maximum tidal amplitude/influenceiii. Enormous contribution for coastal

Fisheriesiv. Only tiger reserve in the saline

marshy mangrove habitat in theWorld.

“Due to the unique features the Sundarbansmangrove is included in the “World Heritage”category”.

Recommendations1. Indian mangroves are subjected to

considerable exploitation due to theextensive population shift to costal areasfor livelihood. Alternate rehabilitationprogrammes to reduce the pressure anddependence on mangroves may controlthis migration.

2. The existing forest rules may also bestrictly enforced to mangroves so thatunlawful entry/encroachment andindiscriminate exploitation can beregulated.

3. Collection of mangrove products may beregulated by appropriate rules.

4. Conversion of mangrove lands for otherpurpose must be strictly prohibited.

5. Coastal area development or any activityin the coastal zone must be associatedwith lost/degraded/degeneratedmangrove area’s reclamation/restorationwherever possible.

6. Budgetary provisions may be providedin the maritime states for surveillance,watch and ward of wetlandecosystems.

7. Special task force/squad may becreated in the maritime state’s, forest

department for surveillance, watch andward of wetland ecosystems.

8. Regular monitoring of the state of art ofmangroves by government organization,Universities and similar agencies forunderstanding the nature and dynamicsof mangrove ecosystems may be done.

9. Methodologies and techniques are to bedeveloped for reliable predictions aboutthe state of mangroves which helps indeciding, if a mangrove area of a certainlocation has the potential to regenerateor artificial restoration is essential.

10. Afforestation programme may bemaintained for transplantation in theappropriate areas.

11. Nursery for mangrove plants may bemaintained for transplantation in theappropriate areas.

12. National Policy on mangrove ecosystemmanagement may be strengthened/formulated for protection of mangroves.

13. Awareness campaign on conservationand management of mangroves amongcoastal population may be intensified.

14. Mangroves, their importance and otherrelated matters may be included in thecurriculum/syllabus of education atvarious levels for HRD formanagement of wetland ecosystems ofthe country.

15. Seminars, symposium, etc may beconducted in the local language itselfwith the participation of local people toaddress issues related with mangrovesconservation and sustainablemanagement.

Prepared by : P. Kaladharan, A Nandakumar,M Rajagopalan and J.P.George, CMFRI, Kochi

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