Integrated fish farming systems refer to the production, integrated management and comprehensive use of aquaculture, agriculture and livestock, with an emphasis on aquaculture. China has a long and rich history of integrated fish farming. Written records from the first and second centuries B.C. documented the integration of aquatic plant cultivation and fish farming.
From the ninth century, records showed fish farming in the paddy field. From the fourteenth to sixteenth centuries, there were records of rotation of fish and grass culture; and by the 1620s, the mulberry-dike fishpond, the integration of fish and livestock farming and complex systems of multiple enterprises integrated with fish farming were developed.
Integrated fish systems, using grass and aquatic plants as fish feeds, are commonly found in many parts of China. These systems are particularly predominant in the irrigated lowland areas of the Changjiang, Pearl and Yangtze River basins. Many of these farms are large, communal ones with cooperative or collective farming, which are commonly found throughout China. Farmers in these areas grow graminea species in various areas of their farms, including fields, small plots of unused land, pond dikes and drained ponds. The grass is then fed directly to the fish as a supplemental feed. In southern China, farmers also use available water resources, such as rivers, lakes, ditches and pools, to cultivate aquatic plants for their use as fish feeds.
Three integrated systems from China, involving grass and/or water hyacinth are presented here: grass-fish, water hyacinth-fish and pig-grass-fish.
Grass species, which can easily be produced on the farm, can serve as low-cost supplemental feeds for fish. Commonly cultured fish species, which can feed directly or indirectly on grass, include grass, silver, bighead and common carps. As seen in Figure 1, grass can be grown along pond boundaries and fed directly to fish. Grass species commonly used include rye, Sudan and napier grasses (see Table 1). Figure 2 outlines a seasonal calendar for grass production within a grass-fish system. The information presented here excludes data for labour and opportunity costs.
Table 1. Summary of important aquatic and terrestrial species used for grass-fish integration.
Parts used are leaf and stem. Conversion factor is amount of fresh grass required to produce 1 kg of fish.
Pond sizes range from about 0.5-1 ha in size with water depths of 2-2.5 m. Net fish yields of up to 6 t/ha have been recorded without supplemental feeding or the use of additional green or animal manures. An area roughly one-half the size of the pond is needed to produce sufficient grass for supplemental feeding. Figure 3 shows that on-farm produced rye grass and Sudan grass can be sufficient to meet fish production feed requirements. Rye grass and Sudan grass can yield up to 112 t/ha/season (fresh weight) and hybrid napier can yield up to 300 t/ha/season (fresh weight).
Grass-fed systems work well in China because:
(a) competition for grass is limited as grazing animals are less important;
(b) large grass carp seed are available;
(c) grass carp are relatively valuable;
and (d) other fish species are available to utilize grass carp wastes in polyculture.
The use of cereal grains as feed supplements in fish production can be costly; using grass species can be much more economical. Production costs related to supplemental feeds are 50 percent lower (per kg of fish produced) for grass-fed vs. cereal grain (barley)-fed fish.
A variety of aquatic plants can be used as supplemental feeds in fish production, among these is the water hyacinth. An area approximately one-half the size of the fishpond is needed to produce enough water hyacinth for supplemental feeding. Water hyacinth can produce up to 300 t/ha/year (fresh weight). Net fish yields can also reach 6 t/ha/year without supplemental feeding or use of additional manures. Pond sizes and stocking rates are the same as in the grass-fish system. Fish input costs using water hyacinth comprise less than 15 percent when compared to cereal grain (barley)-fed fish. Resource flows are outlined in Figure 4. Note that in many countries, water hyacinth is banned and has caused serious problems in lakes, rivers and estuaries.
Pig-grass-fish integration is widely practiced and has good economic returns depending on labour costs. Large-scale pig farms produce large amounts of excreta which, for the purpose of reuse and treatment, are used as fertilizer for high-yielding fodder grasses, which in turn are used as the main feed for herbivorous fish. Pig excreta are only partly applied directly to the fishponds. The excreta of herbivorous fish fertilize the pond water to support the growth of fish. The pond humus can then be used as manure for plant cultivation. Thus, the productivity of both fodder grasses and phytoplankton can be utilized.
Pig-fish and grass-fish components can be integrated to optimize the resource flows for increased productivity (Figure 5). About 45-60 pigs can support 1 ha of grass production per year (225-300 t rye grass and Sudan grass) for a 2-ha pond (6 t/ha/year of fish yield) (Figure 6).
Issues for further consideration
The example shown here has been applied on large-scale state farms, where component enterprises were designed and managed to optimize production, and the required labour force could be appropriated as needed. The example is also widely used in small-scale, family-operated fish farms.
With the recent trends of increasing affluence and subsequent increase in cost of labour, change in market demand, changing needs of the farm households and availability of other livelihood options, there is significant impact on such practices. Many such farms in some areas of China have now switched to feed-based semi-intensive fish culture practices.
Initially the system was based on grass collection from various areas, but the technology was evolved and improved by intensification of grass production (both quality and quantity) and including better balanced fish polycultures, which may be appropriate for other recommendation domains given a similar context.
The relevance of the grass-based system for smallholders may be limited due to considerable requirements for space (adequate land area for growing large amounts of grass to adequately feed the fish) and labour (cutting grass for the fishpond, removing mud and broadcasting onto grass). The opportunity costs of the land for growing pasture grass rather than other crops must be evaluated according to the local situation.
The resource costs of growing the necessary high-quality pasture grasses (which is an important issue in this technology) need to be considered. All grasses need considerable and frequent fertilizer application to yield well and produce grass of acceptable nutritional quality for grass carp. Farmers will need information on how to optimize grass production and quality.
Adopters will need to consider how the labour demands for collecting and growing grass can be managed within the household. In northern Vietnam, women do most of the grass cutting and spend up to 2-3 hours per day on this activity.
In locations in which macrophagous (i.e. grass-eating) fish are nonexistent, alternative management methods can be recommended. Of consideration is also, how much of the grass works as direct feed for the grass carp, and how much as green manure to the pond ecosystem.
Research has shown that water hyacinth has poor palatability for fish compared to other aquatic plants. Usually water hyacinth, which is a banned pest and environmental hazard in many countries, grows in unutilized ponds, ditches and common property waterbodies. The case presented here indicates options to utilize this resource. The weed can also be used to remove nutrients, e.g. for wastewater treatment, although then accumulation of pollutants may become an issue.
Given larger amounts of available pig manure (e.g. from pig farms), and macrophagous fish in a polyculture, the recycling of pig manure onto grassfields, and the subsequent feeding of grass to fish may be an option. Otherwise it may seem more efficient to add the pig manure directly to the fishpond.