黄海大海洋生态系项目 多营养层次的综合海水养殖研究报告 imta ... · 2020....
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黄海大海洋生态系项目
多营养层次的综合海水养殖研究报告
IMTA Report for YS-LME Project
编写:刘慧
中国水产科学研究院黄海水产研究所
中华人民共和国农业农村部
Edited by: Hui Liu
Yellow Sea Fisheries Research Institute,
Chinese Academy of Fishery Sciences,
Ministry of Agriculture and Rural Affairs, PR China
2019.09.27
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目 录
1. Definition and evolvement of Integrated Multi-Trophic Aquaculture ...................................... 2
1.1 Definition of Integrated Multi-Trophic Aquaculture ..................................................... 2
1.2 The history of IMTA ....................................................................................................... 4
2. IMTA Case Study in the Yellow Sea Region ................................................................................ 6
2.1 Case 1. Costal Ocean Longline IMTA in Northern China ................................................ 6
2.1.1 Species composition and ecological principles ................................................. 6
2.1.2 Site selection and construction of the longline IMTA system ........................... 7
2.1.3 Economic and ecological benefits of longline IMTA ........................................ 10
2.2 Case 2. Ecological recirculating mariculture (ERM) ..................................................... 12
2.2.1 Species composition and ecological principles ............................................... 12
2.2.2 Site selection and construction of the pond IMTA system .............................. 13
2.2.3 Economic and ecological benefits of ERM ...................................................... 17
2.3 Case 3. Ecological fishery mode of sea ranch .............................................................. 18
2.3.1 Species composition and ecological principles ............................................... 19
2.3.2 Site selection and construction of the pond IMTA system .............................. 20
2.3.3 Economic and ecological benefits of sea ranching .......................................... 22
3. Conclusion ............................................................................................................................... 23
4. References ............................................................................................................................... 24
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1. Definition and evolvement of Integrated Multi-Trophic
Aquaculture
1.1 Definition of Integrated Multi-Trophic Aquaculture
In 2009, FAO published a technical report Integrated Mariculture: A Global Review (Soto,
2009), which aims to guide the development of mariculture in the world. However, because
of the lack of understanding of China-related information, the report didn’t reflect the true
status of Chinese integrated mariculture (Barrington et al, 2009; Troell, 2009). China is the
country with the longest history, richest experience, and the largest number of mariculture
species and modes in the world. Therefore, without sufficient Chinese information, it is
impossible to truly reflect the theory and practice of integrated mariculture in the world
(Dong, 2011).
Fig. 1 Schematic diagram of Integrated Multi-Trophic aquaculture (IMTA)
(https://www.nationalgeographic.com/foodfeatures/aquaculture/)
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Integrated aquaculture generally refers to the cultivation of different biological species
in the same system or water, or the combination of cultivation of different species in
adjacent waters, or on land and in water, so as to improve the utilization of feed, reduce the
impact on environment, prevent disease and reduce natural disasters, or increase the
general output. Therefore, it is generally considered to be a sustainable aquaculture mode
(Dong, 2011). As a special case of integrated aquaculture, Integrated Multi-Trophic
Aquaculture (IMTA) refers to the culture of organisms at different trophic levels, especially
for raising fed species and non-fed species. In this way, the environmental impact of
aquaculture is reduced, the aquaculture capacity is increased, and the utilization of input
energy and materials in the system is improved.
Fig.2. Complementarity between cultured species in an IMTA system
The fundamental theory of IMTA is that, the organic or inorganic matter (e.g., waste
feed, feces) generated from the fed culture units (e.g., fish, shrimp or other fed species)
provides the nutrients for non-fed culture units (plants, filter-feeding shellfish, or other
non-fed species) within the same culture system. This approach makes efficient use of
nutrients and energy in the system, and mitigates the pressure of aquaculture on the
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ambient ecosystem. It may also improve species diversity and profitability, which contributes
to the sustainable development of aquaculture. The concept of IMTA combines multi-trophic
aquaculture with integrated aquaculture, and it was first proposed by Thierry Chopin, a
Canadian scientist, in 2004.
The practice of IMTA has been often considered a mitigation approach against the
excess nutrients/organic matter generated by intensive aquaculture activities particularly in
marine waters (Soto, 2009), which may impose significant environmental impact. In fact,
IMTA can cover a diverse range of co-culture/farming practices, including more specialized
forms of integration such as rice planting with aquaculture. Integrated mariculture has many
ecological benefits, among which bioremediation is one of the most relevant. However, the
social and economic advantages of IMTA have not really been quantified and reflected, and
because IMTA is linked to the sustainable development of aquaculture, it has great potential
in these respects. Reducing risks is also an advantage and profitable aspect of farming
multiple species in marine environments (as in freshwaters): a diversified product portfolio
increases the resilience of the operation, for instance when facing changing prices for one of
the farmed species or the accidental catastrophic destruction of a crop. However, due to the
price advantage of some cultured species, or due to the investment cost or technical
limitations, China's mariculture once showed a tendency to monoculture; currently in some
mariculture areas for the premium species such as sea cucumber Apostichopus japonicas and
large yellow croaker Larimichthys crocea, this phenomenon still exists.
1.2 The history of IMTA
The earliest records of integrated aquaculture of grass carp Ctenopharyngodon idellus
and rice in China were in the Tang Dynasty, or even earlier. This can be regarded as the
starting point of integrated aquaculture mode in the world, which was a great pioneering
work of the Chinese ancestors, and a major event in the history of global fishery (Dong,
2015).
Since the early 1950s, China scientists began to explain and summarize the practical
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experience of traditional finfish pond culture in China with ecological principles, and have
obtained a large number of research results. The first representative work is Freshwater Fish
Aquaculture in China (Chinese Freshwater Fish Culture Experience Summary Committee,
1961). During this period, the ‘eight-character intensive aquaculture techniques’ were
summarized, covering many aspects such as water, species, feed, density, integration,
rotation, prevention and management. The ecological principles on which these technologies
are based were also preliminarily elaborated. At the same time, the working principle of
guiding aquaculture scientific research and production practice with ecological principles
began to prevail, winning a leading position in the world for China's aquaculture theory,
especially the theory of integrated aquaculture (Dong, 2011).
China's large-scale integrated mariculture began in 1975 with the cultivation of kelp
Laminaria japonica and mussels Mytilus edulis in Penglai, Shandong Province (Xie, 1981).
Almost at the same time, cultivation of mussels with kelp in the same area also obtained
good results in Fuding, Fujian Province (Fu, 1979). In 1984, the development of 1,333 ha
seawater “three-dimensional mariculture” in Changdao County, Shandong Province obtained
very significant economic benefits (Luo et al., 1984). An earlier report on integrated
aquaculture in seawater ponds was the polyculture of shrimp Fenneropenaeus chinensis and
redlip mullet Liza haematocheilus in Ganyu County, Jiangsu Province in 1979 (Wu et al.,
1980). Zhu (1981) also carried out polyculture of shrimp F. chinensis and clam Meretrix
meretrix in Qidong County, Jiangsu Province in 1980, with good outcomes. At present, the
above-mentioned various culture modes are still in use, but the variety is increasingly rich
and the matching proportion of species is getting more reasonable; meanwhile, in order to
cope with the epidemics such as shrimp white spot syndrome (WSSV), shrimp pond
polyculture with bivalves, crabs, finfish and seaweed are also very popular, and all made
good results.
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2. IMTA Case Study in the Yellow Sea Region
2.1 Case 1. Costal Ocean Longline IMTA in Northern China
2.1.1 Species composition and ecological principles
The finfish-seaweed and mollusk-seaweed integrated mariculture, or any other
mariculture modes that are currently popular in China, are nutritionally a unity of the
opposites in terms of cultured organisms. Fed species such as finfish are heterotrophic
organisms, while seaweeds are autotrophic organisms, thus they are ecologically opposite
and complementary. If seaweed is grown in a water body by monoculture, its production
capacity will be limited due to the limitation of nutrients (such as NH3-N, CO2); if finfish is
raised by monoculture, the production capacity will also be limited by dissolved oxygen or
high concentration of ammonia.
However, if finfish and seaweed are co-cultured in a certain proportion, the mutual
beneficial relationship will be shown by seaweed’s utilization of fish wastes and purification
of the water, thereby increasing the aquaculture capacity of the water body. Autotrophic
organisms and heterotrophic organisms, fed species and non-fed species are all unity of the
opposites, and the ratio between them is a precondition for a balanced IMTA system with
high efficiency. The Longline IMTA in China’s inshore waters, as exemplified by Sanggou Bay,
is usually shown by a combination of species at different trophic levels such as
bivalve-seaweed, finfish-bivalve-seaweed, and bivalve-seaweed-sea cucumber, all of which
are widely conducted in coastal bays or regional large water bodies, and constitutes a typical
IMTA farming mode of coastal oceans in China.
Sitting on the eastern tip of Shandong Peninsula, Sanggou Bay is a major mariculture area
for seaweed (output 80,000 t dry wt/a) and molluscs, including oysters Crassostrea gigas
(20,000 t/a), scallops Chlamys farreri and Argopecten irradias (10,000 t/a), abalone Haliotis
discus (2,000 t/a). There are also some shrimp ponds on the intertidal zone and some net cages
for finfish in the inner bay. Aquaculture generates an estimated value of 700 million USD (2016)
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from Sanggou Bay. Seaweed longline culture with Laminaria japonica as the major species
extends from inside of the bay to more than 8 km outside the bay, reaching a water depth of 40
m. Since the growth season of kelp is limited to late fall through early spring, the temperate
seaweed Gracilaria spp is also cultured in Sanggou Bay, during the summer time.
2.1.2 Site selection and construction of the longline IMTA system
Sites for farming mollusc and seaweed using the longline culture system usually require
reasonable shelter from waves and wind, high water quality, adequate tidal flow, depths of
at least 5 m up to 20 m and ample nutrients and phytoplankton supply. The muddy and/or
sandy sediment type is suitable for setting up longline facilities. Furthermore, the site should
have no industrial or sewage pollution, and environmental parameters should meet the
requirements of relevant national water quality standards.
Longline for seaweed culture is usually formed like a grid. The main rope forming the
backbone of the longline structure is also called stem rope, which should be fixed along the
direction of the dominating currents of the seawater. The stem rope is also attached to the
buoys or floats, which provides enough buoyancy for the cultured biomass. The typical
length of each stem rope is 80-100 m, and they are set side by side at a 4.6 m distance
between each other. In order to fix the stem rope, two anchor ropes are attached to both
ends of the stem rope. The length of the anchor rope is generally three times that of the
water depth, and the lower end is fixed to the sea bottom by a gravity anchor or wooden
pegs.
2.1.2.1 Filter-feeding bivalves and seaweed IMTA
Buoys with a 30 cm diameter are fixed on the stem rope at appropriate spaces, so as to
support the mass of growing bivalves etc. The lantern nets containing scallops or oysters are
hung on the stem rope. The space between two lantern nets is 2.3 m, so that a total of 43
nets are hung on one 100 m stem rope.
Horizontal hanging cultivation is typical for kelp longline systems. Each kelp ropes has a
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length of 2.3 m, with 30~32 kelp attached to it. Two kelp ropes are joined together in the
middle, and then attached to two adjacent stem ropes at both ends. The distance between
the neighboring parallel kelp ropes is about 1.15m. When the kelp grows to the thickening
stage (the length of the kelp reaches more than 1.5 m), a small float can be added at the
joint of the two kelp ropes, in order to increase buoyancy and light availability to the kelp,
thus enhancing the productivity. According to the mutual benefit and biological
characteristics of the filter-feeding bivalves and seaweed, Saccharina japonica is the suitable
bioremediation species during winter and spring, while Gracilaria lemaneiformis is more
suitable during summer and autumn.
When the cultured kelp reaches market size, at an average length of about 3 m, it can
be harvested. Harvest from each kelp rope is about 50 kg. According to the 2016 data, the
average yield of kelp is about 15 t per mu (225 t/ha). In the coastal Yellow Sea, kelp is usually
harvested in May through July; kelp for food processing is harvested earlier, and harvest
usually starts in late April to May.
Fig. 3 The structure of a longline system for mollusc - seaweed IMTA (Curtsey of Fang, 2016)
Daily management is necessary to maintain the good growth condition of the organisms,
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which includes the cleaning of fouling organisms, maintaining the facilities, examining the
number of buoys, and monitoring relevant environmental parameters. Moreover, it is
important to keep records so as to trace the products through all stages of production.
2.1.2.2 Abalone, seaweed and sea cucumber IMTA
Abalone needs to consume considerable amount of feed, which is usually fresh or dry
seaweed. In abalone single culture areas, due to high culture density and reduced water
exchange, on top of the low utilization efficiency of diet by the animals, deterioration of
water quality happens very frequently, which in turn affects the health of abalone, and
ultimately affecting the food production function of the aquaculture system. The
implementation of abalone-seaweed-sea cucumber integrated aquaculture helps reduce the
negative effects caused by large-scale abalone aquaculture significantly. In this system, the
seaweed serves as the food for the abalone, while the dissolved and particle wastes
generated by the abalone are taken up by seaweed and sea cucumber. The dissolved oxygen
provided by the seaweed can meet the requirement of the abalone and sea cucumber.
Longline culture, as adapted from seaweed culture longlines, is mostly used in the
integrated aquaculture of abalone-seaweed-sea cucumber. Each aquaculture unit consists of
four lines. The length of each parallel stem rope ranges from 80-100 m with a 5m gap
between each other. The facilities used for abalone aquaculture is called abalone culture
cage, which is hung on the stem rope vertically. The cage has three layers inside, and about
280 abalones at shell lengths of 3.5-4 cm are cultured in each cage. The space between two
cages is 2.5 m so that 30 cages are hung on each stem rope. The layout of kelp rope and
number of kelp planted on the kelp rope is the same as “Filter-feeding bivalves and seaweed
IMTA”. The sea cucumbers, serving as the cleaner in this system, are cultured together with
abalone. 2-3 sea cucumbers at an initial body weight of 60-80 g are cultured in each layer.
Daily maintenance and monitor of the system are also important for success of production.
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Fig. 4 Schematic configuration of a longline system for abalone-seaweed-sea cucumber IMTA
(Curtsey of Fang, 2016)
2.1.3 Economic and ecological benefits of longline IMTA
In the bivalve-seaweed IMTA system, bivalves clear the particulate matter in seawater
by filter-feeding, which helps the photosynthesis of the seaweed. The seaweed utilize the
CO2 and ammonia generated from the respiratory and metabolic process of the mollusc, and
benefit the mollusc by producing dissolved oxygen through photosynthesis. This mutual
beneficial process is not only a good way to keep the balance of O2 and CO2 in the marine
ecosystem, but also to promote the biogeochemical cycle of nitrogen. This kind of IMTA
system is a good solution not only to reduce the negative pressure caused by aquaculture
self-pollution, but also to achieve remarkable economic benefits.
Take oyster-kelp integrated aquaculture as an example, after 6-7 months of farming, 28
individuals are harvested from each kelp rope with an average individual wet weight of about
1.30 kg, then the total yield (wet weight) of each rope is 36.4 kg. According to the ratio of dry
to wet (1:7), the total dry weight of each stem rope is about 452.4 kg, so the gross income of
each stem rope is about 2,714.4 Yuan RMB if the price of the dry kelp is 6 Yuan RMB /kg. The
production of each oyster lantern net is about 12.5 kg, and the total output of each stem
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rope is about 537.5 kg. The net income of each culture unit (4 stem ropes) is about4,140
Yuan RMB (including 1,600 Yuan of kelp and 2,540 Yuan of oysters), if the salary for workers
and costs for materials are deducted. Therefore, the profit from oyster-kelp integrated
aquaculture is significantly higher than monoculture.
In the abalone-seaweed-sea cucumber IMTA system, abalone is cultured in a cage and
fed with seaweeds which is co-cultured on longline, while sea cucumber is co-cultured with
abalone in a cage and fed on the feces and waste feed from abalone inside the cages. The
dissolved inorganic nutrients (N, P and CO2) excreted from abalone and sea cucumber are
absorbed by the seaweed that also produces oxygen. Abalone-seaweed-sea cucumber IMTA
can also produce significant economic benefits.
In one culture unit consisted by four stem ropes of abalone-seaweed-sea cucumber
IMTA system, a total of 33,600 abalone, 1,080 sea cucumbers and 12,000 kelp fronds can be
produced. Kelp culture begins from November to June of the following year. When the kelp
reaches 1 meter long, it can be used to feed the abalone. Abalone reaches commercial size
(8-10 cm) in two years. Each culture unit can produce 900 kg of abalone, valuing more than
60,000 Yuan RMB. During September to May of the following year, the co-cultured sea
cucumbers grow from 60-80g to 150-200 g. The price of live sea cucumber is now 140
Yuan/kg, so that the average output value of sea cucumbers in each cage will be 210 Yuan.
Correspondingly, the output value for each culture unit will be 25,200 Yuan higher than
abalone-seaweed integrated culture, with a net profit increase of 8,400 Yuan as the costs of
sea cucumber seedlings are deducted.
Based on the analysis of ecological and economic benefits, IMTA in the coastal ocean
has obvious advantages over the traditional mode of monoculture. However, due to the
diversification of cultured species, the technical demand will increase, and the cost of
equipment investment and manual handling will also increase accordingly. Although these
are not problems for large companies with strong technical strength and rich farming
experience, they may pose difficulty for small farms. Therefore, carrying out IMTA upgrading
and comprehensive aquaculture reform is not easy for all coastal aquaculture areas in China,
as there are a large number of aquaculture enterprises and a large number of cultured
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species and culture modes.
2.2 Case 2. Ecological recirculating mariculture (ERM)
The main species of pond IMTA in northern China is Litopenaeus vannamei, commonly
known as white-leg shrimp or white shrimp, belonging to Arthropoda, Crustacea,
Malacostraca, Decapoda, Dendrobranchiata, Penaeidae, Litopenaeus. L. vannamei is native
to the coastal waters of Central and South America and has the habit of migration for
breeding offspring. Adults live in offshore waters with high salinity. The newly hatched larvae
and juveniles stay near the estuary and coastal lagoons, which have soft mud bottom, rich in
feed organisms and has low salinities (4-30). When the juveniles reach a body length of 12
cm on average, they start to migrate offshore. Therefore, L. vannamei has wide salinity
adaptability. L. vannamei is the most common species for pond IMTA in China, which is
usually in polyculture with other species; L. vannamei pond IMTA is widely carried out all
along China coasts.
The waste water discharged from the shrimp pond contains a large amount of organic
particles such as phytoplankton, feed debris, and shrimp faeces. These are good food source for
filter-feeding bivalves. In integrated shrimp-bivalve culture, either in the same pond, or in
consecutive ponds so that waste water from shrimp pond is discharged into the bivalve pond, the
phytoplankton and most of the debris in the water can be utilized by filter-feeding bivalves. The
remaining particulate matter that cannot be directly absorbed can be decomposed by
microorganisms, take up by phytoplankton and then indirectly used by bivalves.
2.2.1 Species composition and ecological principles
The main species of shrimp cultured in seawater ponds are Litopenaeus vannamei,
Penaeus monodon, Fenneropenaeus chinensis, and Penaeus japonica etc. Co-cultured species
in shrimp ponds may include: swimming crab Portunus trituberculatus, molluscs such as
razor clam Sinonovacula constricta, Manila clam Ruditapes philippinarum, Meretrix meretrix
etc., finfish such as sea bass Lateolabrax japonicus, sea bream Pagrus major, Sparus
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macrocephalus, globe fish Takifugu rubripes, Mugilogobius spp and other carnivorous fish,
and jellyfish such as Rhopilema esculenta, Rhopilema asamushi, Nemopilema nomurai, and
Rhopilema hispidum. Sometimes, deposit feeder such as sea cucumber Apostichopus
japonicus and polychaete Neanthes japonica are also used as supplementary species in
shrimp pond IMTA.
Pond IMTA fully utilizes the mutual-beneficial relationship among different organisms,
not only by focusing on the combination of different trophic levels, but also by highlighting
the utilization of different water depths and spaces. Different biological characteristics and
the ecological habits of species determine their functions in the pond IMTA system. Because
the pond water body is relatively closed, the exchange of water and materials between the
pond and the external water is relatively easy to control. Therefore, if the proportion of
primary producers and consumers, or fed species and non-fed species is properly matched,
the ecological functions of fish, shrimp, crab, mollusc, and other species can be fully utilized.
2.2.2 Site selection and construction of the pond IMTA system
As a general requirement, the site for building mariculture ponds should have easy
access to water resource, with good water exchange, has good water quality and no
pollution, and has access to electricity and convenient transportation. The seawater quality
should meet the requirements of the People’s Republic of China National “Fishery Water
Quality Standards” (GB1607-89). Salinity and pH of the seawater should be within the
normal range, at 20-32 and 8.0-8.6, respectively.
In view of the lack of a paradigm of pond IMTA in the Yellow Sea region with relatively
complete functions and relatively high ecological efficiency, we would present a case of
land-based IMTA system——Ecological Recirculating Mariculture Mode, in Yongxing Base of
Zhejiang Marine Aquaculture Research Institute. This case is a comprehensive aquaculture
ecological park based on earthen ponds. The park is located on the east coast of Longwan
District, Wenzhou City, Zhejiang Province. The system covers an area of 18.4 ha and consists
of five main functional areas and two supporting facilities. The main functional zones include
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a high elevation intensive culture zone, a seedling production zone, a mollusc culture zone,
an artificial wetland and an ecological purification zone. The supporting facilities are waste
water treatment system and online water quality monitoring system. The flow chart and
layout of the park are as figures 5 and 6.
Fig. 5 Flow chart of the ecological recirculating mariculture mode
(1)High elevation intensive culture zone: covers an area of about 1.67 ha and is
divided into two sections: seven 750 m2 earthen ponds in D zone, and ten 1000 m2 earthen
ponds in F zone. The depth of the ponds is 1.5-2m, gradually deepening from the edge to the
middle, and the sewage outlet is set in the middle, which is connected with two independent
circulating channels leading either to the waste water treatment system or the shellfish
culture zone, according to the concentration of particulate organic matter. If the waste water
contains high concentration of POM, it needs to be recycled by the waste water treatment
system. High elevation intensive culture zone is the main source of nutrients in the ERM.
In the high elevation intensive culture zone, white shrimp P. vannamei is cultured
intensively, producing 2-3 batches of shrimp annually. In order to control the discharge of
waste water per unit time, and reduce the purification pressure of the whole recirculating
system, the average yield of shrimp is limited to 1.5-2.5kg/m2, which is 2-3 times higher than
the usual stocking density for shrimp pond.
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Fig. 6 Layout of the ecological recirculating mariculture farm
(2)Hatchery zone: including seven greenhouses, which are built by brick walls and
steel frames supporting automatic sunshade roof. There are 260 cement tanks of different
sizes in the greenhouses, with a total seedling rearing water body of 10,000 m2. The
hatcheries mainly produce bivalve and shrimp seedlings. The main species are: Tegillarca
granosa, Cyclina sinensis, Meritrix meritrix, Sinonovacula constricta, Ruditapes philipinarium,
etc. About 8-10 billion seedlings are produced annually, and the output value can reach 3
million Yuan. After a short period post settlement, the shellfish larvae can be cultured with
the algae-rich water from the high elevation shrimp ponds. The rearing of shrimp larvae
begins with nauplii, and reaches postlarvae after 12-15 days of cultivation. Annual
production of shrimp seedlings is 200 million, with an output value of about 3 million Yuan.
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(3)Mollusc culture zone: The total area is 1.33 ha, with a total of six conventional
earthen ponds. 2/3 of pond area in the middle is a shallow sandy flat, surrounded by a ring
groove along the pond circumference, at a depth of 1.2-1.5m. The pond is equipped with a
bottom aeration system to increase pond culture capacity. The pond is mainly used for
bivalve farming, with an annual output of 50-100 t large-size bivalves. The mollusc culture
flat in the middle is quarantined by a net, so that Scylla serrata, Exopalaemon carinicauda,
Mugil cephalus, Sciaenops ocellatus, Acanthopagrus schlegelii, and Siganusoramin spp are
co-cultured in the grooves, in order to improve water purification and economic benefits of
the system.
Fig. 7 Sectional view of the mollusc culture pond
(4)Artificial wetland: making use of mangroves’ northernmost distribution area in
China, covering an area of 8500 m2. It is mainly planted Kandelia candel, and a small amount
of Aegiceras corniculatum. Half-mangrove Cerbera manghas and Vetiveria zizanioides etc.
are planted on the bank. The finfish Boleophthalmus pectinirostris is also stocked on the
mangrove wetlands to increase the permeability of the substrate and improve economic
efficiency. Mangroves can reduce the suspended solids, COD, nitrogen, phosphorus, heavy
metals, CO2 and other elements in the atmosphere through plant absorption, soil surface
absorption, chemical precipitation and microbial metabolism, so as to filter organic matter
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and pollutants, and purify the atmosphere and reduce water pollution.
(5)Ecological purification zone: consists of two purification ponds with a total area of
3.4ha and a water depth of about 4m. The pond is stocked with finfish such as Mugil
cephalus, Larimichthys crocea, Siganusoramin spp., Sciaenops ocellatus, Acanthopagrus
schlegelii etc. Seawater vegetable artificial floating island is built on the water in one of the
ponds, which is both shading for dark sedimentation and nutrient remover through the
absorption of plant roots. Ecological purification ponds will build a stable ecosystem in the
pond by stocking a variety of organisms, such as benthic filter-feeding bivalves, omnivorous
fish, carnivorous fish, etc., together with the natural zooplankton and phytoplankton, to
achieve the purpose of water purification. Ecological purification pond acts also as reservoir
of the entire ERM, from which water can be drawn and used directly for rearing shrimp and
bivalve seedlings.
2.2.3 Economic and ecological benefits of ERM
Since its establishment in 2012, the ERM system has been operating smoothly for many
years with significant economic benefits. In 2015, a total of 49.8 t of large-size white shrimp,
45.1 t of market size bivalves and 8.1 billion bivalve seedlings were produced, with a gross
profit of 5,662,100 Yuan RMB and a unit profit of 20,500 Yuan per mu; whereas the profit of
conventional earthen pond monoculture is generally 14,400 Yuan per mu. Therefore, the
overall benefit of ERM is more than 20% higher than that of traditional pond monoculture.
ERM can greatly increase the productivity and income of shrimp farmers, and has broad
prospects for extension. In view of ecological benefits, ERM does not discharge wastewater
to the surrounding area throughout the aquaculture process; it only needs a small amount of
water supplement at regular intervals. Meanwhile, because the system is relatively closed,
through accurate monitoring and modulations, the water quality can be controlled and
relatively stable, pathogenic microorganisms are not introduced and have the chance to
proliferate in the system. Therefore, not only the economic benefits of ERM are improved,
but also the quality of aquatic products is guaranteed.
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However, currently ERM still sees limited application in China, while integrated pond
mariculture mode is more common, as represented by co-culture of shrimp and one or a few
other species. Dong (2015b) studied the effects of monoculture of Litopenaeus vannamei
and its polyculture structure with clam Cyclina sinensis and Gracilaria lichevoides. The results
showed that under the experimental conditions, the optimal species combination of the
polyculture system was: 30 ind. shrimp, 30 ind. clam and 200 g Gracilaria per square meter.
In this system, the photosynthetic energy conversion efficiency was 0.81%, total energy
conversion efficiency was 92.07%, utilization rate of input N and P was 35.6% and 17.2%,
respectively. The optimized aquaculture mode has not only higher shrimp yield and
economic benefits, but also has higher ecological efficiency than monoculture of shrimp.
However, it should be noted that even with the above-mentioned optimal culture structure,
the utilization rate of N and P in the feed is only 35.6% and 17.2%, and most of the waste
feed are discharged offshore or deposited in the pond sediment. It can be concluded that, as
a type of IMTA, integrated pond mariculture may obtain widely different economic and
ecological benefits; it is difficult for pond IMTA to achieve environmental-friendly and
ecological-efficient purposes without systematic design and precise management.
2.3 Case 3. Ecological fishery mode of sea ranch
Sea ranch is a fisheries approach integrating stock enhancement and aquaculture.
Theoretically, sea ranch is an ecosystem with integrated functions of environmental
protection, resource conservation and sustainable fishery output. Sea ranch is built in a
suitable sea area by modern engineering techniques and management modes, through
habitat restoration and artificial stock enhancement based on ecological principles, so as to
make full use of the natural productivity. The concept of sea ranching has been evolving in
China for a long time. In the 1940s, Chinese marine biologist Zhu Shuping put forward the
idea that “water is a pasture for fish” and advocated “seedling fish and developing sea ranch”.
Since the beginning of the 21st century, China coastal provinces and cities have made full use
of marine resources, actively engaged in the construction of artificial reefs and seaweed beds,
and vigorously developed sea ranches. The target for sea ranch construction is increasing the
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production of certain economic seafood to ensure stable and sustained growth of aquatic
resources; and protecting marine ecosystems and achieving sustainable ecological fishery at
the same time.
2.3.1 Species composition and ecological principles
By comprehensive construction and management of coastal ecosystems, a sea ranch
may support a wide range of biological species including both the released and natural
stocks, covering all trophic levels from producers, consumers to decomposers. Artificial reefs
provide substrates for seaweed and sedentary organisms; varied flow fields and flow
patterns formed in the reef area, provide habitats for various aquatic organisms to inhabit,
reproduce, grow, and avoid enemies. Seaweed transplant and seagrass bed construction are
vital for restoring seabed ecology and reversing desertification of the sea, since this can both
purify the water and improve the sediment quality, as well as slow down the mariculture
greenhouse effect and prevent algal blooms. Through the construction of demonstration sea
ranches, it is possible to restore and improve the recruitment of fishery stock and
biodiversity at the demonstration area and its surrounding waters, enhance the ecological
environment quality and ecosystem service functions of the ocean, and promote the
sustainable and healthy development of marine fisheries.
Sea ranch is a unity of fishery production and resource conservation, and management
is the core of sea ranching. According to the requirements of “cultivating the sea”, it is
necessary to integrate the fragmented sea space and scientifically utilize the whole sea area.
In order to “herding the fish”, it is necessary to implement layered three-dimensional
ecological farming, to realize the harmonious symbiosis of finfish, shellfish, seaweed and sea
cucumbers. To highlight “operation” and "management", it is necessary to control input
materials, product marketing, safe production, monitoring and early warning, and other
management procedures; to build a fisheries industry chain, reduce farming costs and risks,
simultaneously improve fish farmer's income and enterprise development, and boost marine
ecology and production efficiency at the same time. So far, a total of 148 sea ranches were
constructed in the Yellow Sea region, covering an area of 346.7 km2; 18 million empty cubic
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meters of artificial reefs have been placed on the seabed, covering a total area of 157km2.
About 33 national demonstration sea ranches have been built in Shandong Province. Here
we would take Xunshan Group Co., Ltd. in Rongcheng City as an example to introduce the
ecological fishery mode of sea ranch.
2.3.2 Site selection and construction of the pond IMTA system
In recent years, Xunshan Group has actively responded to the Opinions of the of
Shandong Provincial Government on Promoting the Construction of "Ocean Granary", by
focusing on the development of marine economy and promoting marine fisheries. Relying on
the S&T advantages of the Marine Shellfish Research and Development Center and the
company’s resource advantages, Xunshan Group focused on the development of ecological
mariculture, actively carried out recreational fishery, and built up a 3200 ha sea ranch. On
this sea ranch, about 2.5 billion units of kelp, abalone, scallop, sea cucumber and Sea Squirts
are cultured each year, with an annual output of nearly 400,000 t. Xunshan Group has won
the honorary title of National Demonstration Sea Ranch and National Recreational Fishery
Demonstration Base.
Create an “Integrated Multi-Trophic Ecological Mode” to optimize ecological
mariculture. In collaboration with Yellow Sea Fisheries Research Institute, Chinese Academy
of Fishery Sciences, the company operated with a new mode of IMTA, which combines
seaweed, shellfish, sea cucumbers and finfish in a strict proportion, and carries out
three-dimensional mariculture making full use of all water layers. As a result, different
cultured species provide nutrition to each other and the general yield is increased. The effect
of oxygen and carbon fixation is also significantly improved, which effectively alleviate
mariculture impact, avoid eutrophication of water and occurrence of red tides.
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Fig. 8 Schematic map 1 of Xunshan sea ranch (I)
Fig. 9 Schematic map 1 of Xunshan sea ranch (II)
Construct artificial reefs and remediate the coastal marine ecosystems. In 2006, the
company took the lead in Shandong Province to implement artificial reef construction
project. In the first phase, a total of 53.71 million Yuan RMB was invested, 400,000 empty
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squares of various reefs were introduced and 131 ha of artificial reef area was built, and 200
million units of seaweed and shellfish were released in that area. At present, the company is
carrying out the construction of a new 53 ha sea ranch, with plans to invest 30 million Yuan
RMB, introduce 37,000 empty squares of ecological reefs, build 6 sets of multifunctional
supervision platforms, and plant 33 ha of seaweed beds. The continued artificial reef
construction and three-dimensional ecological mariculture have increased the
comprehensive benefits of the sea ranch by more than 26%.
Implement enhancement release and restore natural fishery resources. Along with the
construction of sea ranch, the company administered enhancement release of mariculture
species such as Sebastodes fuscescens, Japanese flounder Paralichthys olivaceus and other
fishes, as well as abalone Haliotis discus, sea urchin Anthocidaris crassispina and sea
cucumber A. stichopus. After more than ten years of enhancement and proliferation, the
natural fishery resources in the sea ranch have increased significantly. Abalone, for example,
which was not an aboriginal species, has already formed a stable wild population in the sea
ranch. And according to the survey and fishermen report, other catch fishery species have
also increased significantly in quantity and individual sizes in recent years.
2.3.3 Economic and ecological benefits of sea ranching
According to the experience of sea ranching at home and abroad, each empty cubic
meter artificial reef area can increase the annual fish catch by 10 kg in average, compared to
the general sea area without reef. At present, China has built 86 national demonstration sea
ranches, and the total annual economic benefits brought by comprehensive enhancement
fisheries and seaweed transplants are estimated to be over 15 billion Yuan RMB. A
preliminary estimation of the Ministry of Agriculture and Rural Affairs tells that, China's sea
ranches produce direct economic benefits of 31.9 billion Yuan and ecological benefits of 60.4
billion Yuan annually, with annual carbon sequestration of 190,000 t, reduction of 16,844 t
nitrogen and 1,684 t phosphorus, and more than 16 million visitors were received for
recreational fishery.
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However, the history for sea ranching in China is relatively short, and the construction
and management experience is not rich enough. The basic biology and ecology research on
sea ranch is still insufficient. A few number of sea ranches have shown unsatisfactory records
in terms of economic efficiency and input-output ratio, restoration of natural ecosystem
structure and functions, and sustainable development of the industry. To this end, we should
strengthen the physiological and ecological research on the enhancement species for sea
ranches, adopt appropriate, reasonable and targeted environmental monitoring methods
based on scientific assessment, and conduct continuous observations on all sea ranches, in
order to realize risk management and control, and establish early warning mechanisms.
3. Conclusion
IMTA is an “ecologically harmonious” production mode based on the basic principles of
aquaculture ecology. The core of aquaculture ecology and mode construction is to build
aquaculture ecosystems with balanced production, consumption and decomposition
functions, so as to improve the ecological efficiency of the system and increase the effective
accumulation of aquaculture biomass in the recycling process, thereby maximizing aquatic
food production and reducing negative impacts on the environment. In recent years, with
the expansion of large scale intensive fed aquaculture, the environmental impact of
aquaculture has attracted more and more attention from countries around the world. As an
environmental-friendly approach, IMTA has played a significant role in reducing aquaculture
impact, coping with aquaculture diseases, and improving the industry's resilience to risks.
However, even after optimization, some IMTA modes still show poor records in pollution
reduction; e.g. the utilization of N and P in feed is only 35.6% and 17.2%, and most of the
rest are discharged offshore or deposited in the pond sediments (Dong, 2015b). In order to
develop more efficient and environmental-friendly IMTA modes, we must further study the
ecological characteristics of the cultured organisms, and understand the structure and
function of the aquaculture ecosystem. Based on these knowledge, we shall then build
ecologically intensive production systems, to meet people's growing demand for aquatic
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products in context of environmental protection, as well as economic and social
development.
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