Integrating aquaculture - more to fish farming than fish
The greatest variety and development of agro-pisciculture farming systems are found in China but the integration of aquaculture with agriculture is common in different forms across the Asian continent. These small-scale traditional systems promote diversity and sustainability and there is enormous potential for the system to be adapted to other regions in Asia and Africa where there is a demand for fish products to be farmed on a small, but ecologically sound, scale.
Perhaps the best known system in China is the mulberry dike-fishpond system in which mulberry is raised on the pond dike and the leaves are fed to silkworms. Silkworm excreta and pupae are fishpond inputs and the enriched pond mud is then used to fertilize the mulberry. Rice-fish systems are also well known across Asia (see Rice-fish culture: supporting the rural poor).
Away from the paddy fields, livestock may be integrated with fish and crops where every constituent in the system helps to increase production and income. The water stored in farm ponds can be used to extend crop production into dry seasons, thereby increasing total production and attracting premium prices for out-of-season produce; increased production also provides by-products for feeding livestock (cattle, small ruminants, rabbits and poultry); livestock manures, household waste and cereal brans added to ponds feed aquatic plants and animals that in turn feed the fish; and finally, the mud that accumulates as sediment can be used to fertilize the land for fruit and vegetable crops. Just as the integration of trees into crop and livestock production on farms (agroforestry) has provided benefits that reflect a synergy between the various elements, similarly agro-pisciculture can be seen to offer farmers more than just fish as an extra farm crop. Overall, crop yields are increased, fish, fruit and vegetables enrich family diets, greater surpluses provide greater income and, finally, soils are not continuously degraded but made more fertile. It is also important to note that whilst waste is reduced and water quality is maintained, farmers are also more circumspect in their use of pesticides and other chemicals so that pollution is generally avoided.
This system that has worked so well for millennia could help to break the double downward spiral of falling food production and declining soil fertility which affects so many regions in Asia and Africa. Integrated aquaculture systems involve many variables and are therefore highly site-specific. However, providing that soils are water retentive, this integrated system, which promotes species diversification and nutrient recycling, can make even the most marginal lands more productive. Fish is also a popular food but marine catches are falling and even where production from inland waters is available, demand often outstrips supply. Yields of farmed fish in integrated systems cannot be expected to make good the shortage but the additional benefits often exceed the simple value of the harvested fish.
The density of fish that can be maintained in a pond is largely related to the availability of food. As a result, integrated agriculture-aquaculture systems are very flexible and a wide range of the raw materials available can be used. A comparison of different levels of pond management shows that whereas unfertilized, poorly-managed ponds yield 50-200 kg/ha/yr, ponds which benefit from agricultural waste feeding and better stock management can increase yields to 5000-10,000 kg/ha/yr.
Actual yield depends also on the species of fish stocked, as different species feed on different organisms and plant matter. Fish in vegetation-fed systems include the Chinese grass carp (Ctenopharyngodon idella), giant gourami (Osphronemus goramy) and silver barb (Barbodes [=Puntius] gonionotus) which are common in traditional systems in south-east Asia. A wide range of Chinese and Indian carp and tilapia species are suited to manure-fed systems (e.g. Common carp, Cyprinus carpio and Nile tilapia, Oreochromis niloticus) whilst walking catfish (Clarias spp.) are more carnivorous. Yield can also be affected by availability of fry (young fish) or water, climate changes, and the need to drain and harvest ponds. 6000 kg/ha/yr would therefore be an excellent yield for most ponds.
Unrealistic expectations of fish yield has often contributed to the failure to establish fish culture in new regions. Many African countries were introduced to pond fish culture as early as the 1950s but many projects failed as the new system was promoted as a separate rather than an integrated farm enterprise and techniques were inadequately explained to farmers who were completely new to the concept. Many of them failed to grasp the importance of maintaining water quality and correct feeding, and very often there was no assured supply of fingerlings for re-stocking.
Much has been learnt from mistakes made in the past and several international organisations are actively promoting agro-pisciculture in Africa and Asia. FAO works in the SADC countries through the ALCOM development programme while CIRAD is active in much of francophone Africa and ICLARM in Ghana and Malawi. Many West African countries are also benefiting from the demonstration and teaching of integrated agro-pisciculture at the African NGO Songhai Centre in Porto Novo, Benin. In Asia, development and extension work is currently being carried out by CARE and DFID in Bangladesh, AIT in Laos, Cambodia and Thailand, ICLARM/IRRI in Bangladesh, Vietnam and the Philippines, and the SCALE and PADEK aquaculture projects in Cambodia, amongst many others.
Much has still to be learned about the factors that influence the success or failure of efforts to establish integrated agriculture-aquaculture systems. If agro-pisciculture is to be successful, government assistance will be essential for training, initial supply of fingerlings and advice on management while farmers gain experience. Equally importantly, as Mark Prein, Program Leader for the Integrated Aquaculture-Agriculture Systems for ICLARM concludes, "Farmers have to recognise for themselves that there is need to improve their situation. If they are not able to observe the benefits, to understand how their farming system can be realistically enhanced and to participate in discussing how that process should happen, then the successful integration of aquaculture into existing agricultural systems, however beneficial, will not occur."