The Characteristics of Integrated Fish Farming in China
| NACA/WP/84/12 | December 1984 |
|
The Characteristics of Integrated Fish Farming in China |
by
Hu Bao-Tong and Yang Hua-zhu
Regional Lead Centre in China
Asian-Pacific Regional Research and Training Centre
for Integrated Fish Farming, Wuxi, China
NETWORK OF AQUACULTURE CENTRES IN ASIA
Bangkok, Thailand
December 1984
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China has a long history in integrated fish farming with its own set of technology. Since liberation, the government placed high emphasis to develop pond culture and its various integration with agriculture and animal husbandry. This has greatly enhanced the rapid development of pond fishery in the country. Various integrated fish farming models have evolved according to different giographical and climatical conditions in the country as well as the local agricultural characteristics, living conditions and traditional practices of the region.
China is a vast country with a large population and varied natural environments. The economic conditions of each locality and the conditions for fish production are also different. The activities involved in integrated fish farms varied considerably in types and scale of integration. Hence most fish farms established complex integrated farming and management systems forming into a sophisticated structural network.
The Pearl River delta of China is located south of the Tropics of Cancer. Its annual solar radiation is 110 Kcal/cm2 but averaging 60 Kcal/cm2. Average temperature is about 22°C; 2–3 days of frost a year; more rain and high temperature in summer with extreme high temperature recorded at 37°C and relative humidity 76–85%; annual sunshine between 2000 and 2500 hours. Such climatical conditions are conducive for the cultivation of mulberry trees, sericulture and fish farming. Hence, the farmers in the Pearl River delta through practical experience, have been able to take advantage of the environmental characteristics of the vast land and water resources by integrating mulberry cultivation and sericulture with fish farming which lead to the establishment of a complete, scientific “mulberry plot-fish pond” man-made ecosystem.
Even if located in the same geographical zone, the level and types of integrated fish farming by various production units are different. The Holei Fish Farm, Xinan Fish Farm, Holei Commune Fishery Brigade, Wangzhuang Brigade Fish Farm as well as the Municipal Fish Culture Farm in Wuxi practiced different types and level of integration. Located in the western suburbs of Wuxi, Liutan Production Brigade of the Liberation Commune has recently incorporated agriculture, secondary industry, fisheries and commerce into its integrated management structure. The integrated fish farm of the Brigade was established in 1980. The farm site was earlier a 260 mu1 (17.3 ha.), low value paddy field, subjected to annual flooding and with very low yield of agricultural crops. Based on the topography of the paddy lowland, the farmers in the winter of 1979 restructured the land into 160 mu (10.6 ha.) of fish ponds which were completed in the spring of 1980. The farm consists of 15 rearing ponds of total size 180 mu (8 ha.), 11 fingerling ponds of total size 40 mu (2.67 ha.) including about 20 mu (1.33 ha.) of pond dikes for the cultivation of English rye grass (Lolium pereme) sow thistle (Lactuca tenticulata), etc. Liutan Brigade also utilized watercane shoots field to cultivate duckweeds with average yield of 2500–3000 kg/mu. With this advantageous supply of green fodder, grass carp and Wuchang fish (Megalobrama sp.) become the main culture species yielding 350 kg/ mu or 45% of the total pond fish production. This demonstrates that only through maximal utilization of natural environments and the agricultural characteristics of the regions concerned can one attain maximal efficiency of the integrated fish farming system.
The socio-economic conditions should be considered in developing integrated fish farming. Development of various types of integration and management should be based on the harmonious relationship between the socio-economic conditions and agricultural production which is regulated by natural environment and regional climatical differences. Since development of integrated fish farming is site-specific and the conditions of each site are different and complicated either from the macro or micro view points, the linkage between the various components of integrated fish farms in China become a complex metrix of structural network. Apart from small-scale, individual farm, simple models involving mono-integration of fish-cum-animal husbandry, fish-cum-poultry or fish-cum-crops are now not frequently practiced.
The integrated system of fish farming in China is rather complicated involving various forms of integrations and methods in the utilization of organic wastes. The animal excreta alone can be effectively utilized through employing various methods and techniques.
Fresh animal manure, mixed compost and biogas sludges can be applied directly to the fish ponds or indirectly through one or two steps in the production cycle such as producing earthworms or other animal-based feeds or through growing of fodder crop for feeding fish.
Within the system of integrated fish farming, the types of livestocks to be raised with the fish depends on the compatibility of the species of livestock and their biological habits with the fish stocked in ponds. Pigsties, poultry coops and pens for ducks and geese can be constructed on the dikes or above the ponds. Fresh manure thus enter the ponds directly, hence avoiding energy losses due to processing of manure and transportation. Furthermore, the droppings of livestock are not fully digested and hence can be directly utilized. Maar (1956) reported that 70% pig manure can be digested by fish. Le Mare (1952) had observed that when food passed through the gut of pig, it mixed with the digestive enzymes and when excreted, digestion continued to take place. Hence, through the intake of fresh manure, the fish obtain external enzymes. Therefore, direct application of manure to the pond has its food value. Furthermore, in livestock farms there are bound to have left-over feeds or spilled feeds. According to our survey 10–20% of total feed given to ducks are spilled. The amount of wheat-bran wastes daily per duck is estimated to be 23–30g. Such organic waste can be washed into the fish pond providing additional food to the fish. Apparently, from the view point of organic or energy input, direct utilization of fresh manure can effectively and efficiently convert organic waste into fishery products.
The slurry from biogas fermentation is used for fertilizing fish pond. Manure from pigs, cattle and other animals are mixed in proper proportion with green manure in moist condition and are allowed to ferment in closed anaerobic conditions for biogas production; the effluent and sludge are channeled into the fish ponds. The biogas can be used as the energy source for feed preparation, etc.
Experiments have also been conducted to compare the oxygen level and rate of organic sedimentation in fish ponds treated with fermented pig manure and untreated fresh pig dung. During production period, oxygen content of the surface water at 4–5 am has been found to be the lowest. However, ponds treated with fermented manure always have high oxygen content than those treated with fresh manure. From May to mid-July the oxygen level in pond treated with fermented manure was 2.0–2.4 mg/l while that of pond with fresh pig dung was 1.0–2.0; the value recorded in late July-August were 0.8–2.0 mg/l and 0.7–1.2 mg/l respectively for the two treatments. Measurements at 1400 hours 0.5 m from the water surface, showed that the oxygen content of pond with fermented manure was 13–16 mg/l. This shows that the oxygen concentration of pond treated with fermented manure is higher than that of pond with fresh manure. The quantity of sediments accumulated in the two types of ponds is also different. Pond treated with fermented manure has accumulated 10 cm of pond mud while 20 cm thick of bottom sediments was found in ponds treated with fresh manure. The amount of organic remains in the pond mud was 1.8% in the former and 2.1% in the latter.
The fertilization efficiency is somewhat changed in fermented sludges. The ammonium (NH4) content of fermented manure increased by 2–4 times after fermentation and the available nitrogen constitutes 50–70% of total nitrogen. Even the rate of efficiency in manure application at different stages is more effective in fermented manure than fresh manure as in fact the fermented effluent is, in essence, ammonical fertilizer. The C/N ratio in the sludges is also correspondingly reduced, generally between 12.6–23.5, decomposition is faster, although it is a type of slow-acting manure. Apparently, the fermented effluent can be used as a source for additional manure. Approximately 50 kg of fermented effluent can produce 0.5 kg of filter feeding fish. Hence, the utilization of biogas fermented effluent to grow fish can also inprove the water quality, maintain healthy environmental conditions in pond and is also an efficient means to improve the quality of manure fertilizer for fish production.
Throughout the process of biogas fermentation, the nutritive element N.P.K. contained in the fresh animal manure remain in the fermented manure, except partial loss of N. element. However, 40–50% of the dry matter in the raw materials in the manure are also digested by carbon fixing bacteria resulting in the release of biogas (CH4). After applying the fermented manure in the fish pond, multiplication of micro-organisms is restricted by the “substrates” and hence a decline in the microbial density. Micro-organisms is the primary base of the heterotrophic food-chain in a manure-loaded fish pond and is also directly taken in by filter feeding fish. This may result in reduction of natural food biomass in the fish pond. Thus the effective economic utilization of fermented and fresh manure required further study.
Mixed compost is usually applied to crops. the Wangshizhu Production Brigade in Wuxi using the compost of pond mud, rice straws and green manure as the base manure for crops. But ‘Tachao’ compost is mostly used in the fish ponds. ‘Tachao’ compost is piled in heaps at corner of the fish pond to allow fermentation and decomposition so as to raise the primary standing crop of the fish pond. However, it is essential to constantly expose the inner portion of the heap of the compost in order to prevent building up of anaerobic condition which not only reduces the energy resources of the green manure but also may pollute the water quality.
Zhangzhuang Production Brigade in Suchow conducted experiments on production of fish through the cultivation of green fodder using organic manure as fertilizer. It was found that 20 kg of nightsoil (80% of which is water) can produce 0.5 kg of fish or 14 kg of green fodder such as English rye grass. Experiments showed that 13.75 kg of green fodder can produce 0.5 kg of grass carp and Wuchang fish while the excretion of these species can produce 0.3 kg of silver and bighead carps and Tilapia. Hence, 50 kg of nightsoil can produce sufficient green fodder to yield 1.63 kg of fresh fishes. Such production is 63% higher than direct utilization of animal manure for production of filter feeding fish. It was also found that 50 kg of pig manure can produce 37.5 kg of green fodder and when fed to herbivirous fish, will yield 1.365 kg of fish and 0.82 kg of filter feeding fish. Therefore, 50 kg of pig manure can yield 1 kg of filter feeding fish (convertion coefficient of pig manure to fish flesh is 50) When applied directly into the fish pond but 2.185 kg of fish can be produced through production of the English rye-grass. The green fodders, hence increasing production by 11.85%. The quality of fish is also raised and economic efficiency increased by 197.36%. The Zhangzhuang Production Brigade initially applied organic manure directly to fish pond. A 7.5 kg pigling when grown to 75 kg yields 2000–2500 kg of pig manure, when applied directly to fish pond was found to yield 40–50 kg of filter feeding fish. However, if the manure are used firstly to produce green fodder, a production of 87.4–109.25 kg can be attained. The manure from each pig can increase economic returns by 60–75 yuan2, after deducting labour expenses in planting the grasses, the net income is 48.4–60.5 yuan.
In general, integrated fish farms in China adopt various methods in the utilization of organic wastes for fish production either directly or indirectly through various steps in the production cycle. The cultivation of green fodders as one of the steps towards fish production has the following three major advantages: (1) improve the ecological conditions of fish pond and easy to maintain the water quality in the ponds; (2) upgrade the quality of fishery product and (3) increase the economic efficiency.
The polyculture system of fish farming is developed through the accumulation of long experience of the Chinese people in fish production in selecting compatible species of various feeding habits in relation to the ecological niches of the pond ecosystem. Not only filter feeding fish are reared in ponds, herbivorous, carnivorous and omnivorous species are also polycultured to maximize utilization of the available space and natural food in the pond as well as supplementary feeds, thus the stocking density can be increased. The application of the common practice in stocking and harvesting by rotation as well as the use of aerators in ponds are important measures in increasing pond fish production.
Integrated fish farm is also the main source for various type of feeds and fertilizers ensuring sufficient food supply for various species polycultures in pond. The application of organic manure or ‘Tachao’ compost in ponds has resulted in complex food webs in the pond and creating a variety of trophic niches. Green fodder can be used to feed herbivorous species and fine feeds for carnivorous species. Due to the availability and adequate supply of various feeds, the fish farms in Wuxi cultivate more than 8 species of fish in each pond.
Integrated fish farming in a vast country like China exhibits pronounced regional variation due to the availability of different types of feeds, fertilizers and cultured species. In general, between 5–8 species of food fishes are polycultured of which 1–2 species are classified as the “main species” which are the target species for cultivation and management. The remaining species are known as “secondary species” which are stocked in lesser quantity. The “main species” as a whole have a significant impact in increasing production efficiency.
The integrated fish farms in Wuxi adopt polyculture of various species. Production from 66.7 ha.-large water area for food fish production has exceeded 11,250 kg/ha. Individual ponds with intensified integrated farming practices have attained much higher yields, being 29,827.5 kg/ha in 1979, 32,160 kg/ha in 1980 and 32,235 kg/ha in 1982.
The use of animal manure to produce omnivorous such as earthworms or food organisms for carnivorous fish though, increases the production steps from organic waste to fish, certainly has its advantages from the hygienic point of view. However, its economic efficiency and revenue as a result of the increase in the steps of fish production remains a subject of research.
Maar, A. 1956. Tilapia culture in farm dams of Southern Rhodesia. Rhodesia Agric. J. 53(5) : 667–687.
Le Mare, D.W. 1952. Pig rearing, fish-farming and vegetable growing. Malayan Agric. J. 35(3) : 156–166.
Acknowledgements are due to Mr. Min Kuan-hong for the translation of the paper into English and to the NACA international staff for the various assistance rendered.
