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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