20. Biotechnology in fishfarms: integrated farming or transgenic fish?
Biotechnology and Development Monitor No. 7, 1991, pp. 3-6
For many developing countries fish trade represents a significant source of hard currency. Although the developing countries' share in world fish exports remained stable at 45 per cent, net fish exports from developing countries doubled between 1985 and 1989 to US$ 10,5 billion.
Industrialized countries accounted for about 90 per cent of total fish imports in 1989. Aquaculture had already its share in the net export increase, and the application of biotechnology may boost fish exports even more.
Demand for fish is soaring worldwide. It appears unlikely that the increasing demand can be met through increased natural harvest.
Aquaculture could help to meet increasing demand, and biotechnology can make a contribution to improve aquaculture yields.
In Asia, where the bulk of aquacultural products is produced, aquaculture has a long-standing tradition as an extensive low input production system, practiced by resource-poor farmers. Recent interest in aquaculture biotechnology in industrialized countries could have a positive spin-off for these systems.
To be effectively applied to small-scale systems, aquacultural biotechnology methods should start from the more traditional technologies already in use. The efficiency and relevance of these technologies are impressive.
Organic agricultural wastes can be recycled as fish feed. Rice bran, for example, or the brown crust of rice which become available after rice polishing, possibly mixed with mustard or ground nut oil cake, is a very good feed for fish. Soybean cake and wine residues are also given as feed to carps, while grass carps are fed with chopped soft grass and vegetable tops. Wastes from livestock and poultry are recycled too, in some systems by dropping the manure directly into the ponds, thereby raising the production of algae, protozoa and zooplankton.
Mahua oil cake, a residue from oil extraction, is used in India to kill predators in the ponds before fingerlings are stocked. Mahua cake works as poison at the initial stage, but loses all its toxicity after 15-20 days and is then valuable as fertilizer. In Malaysia teaseed cake is used to kill predators.
For cleaning the ponds, duck weed is used in India. To increase alkalinity, banana stem cuttings are allowed to rot in the water.
Planting of tamarind leaves and stems have the effect of decreasing alkalinity of pond waters. Lotus plants maintain oxygen balance in ponds.
Widely adopted in southeast Asia also, is polyculture. In this system, a compatible group of 3 to 6 non-predator fish species of different feeding habits are introduced together in the same pond so that all types of food produced either at column, bottom or surface, are effectively consumed by fishes.
In order to be helpful, biotechnology should be integrated with these traditional methods. Newly introduced techniques must be comprehensible to farmers, and should use materials locally available.
Much of the current biotechnology research, however, seems to be directed at high input aquaculture production that requires, e.g. a well trained staff, pumps, tubewells and formulated feeds. To justify these costs, farmers need to produce high value products which often go for export, since in developing countries only the relatively wealthy can afford to eat their products. In poor communities, even the costs involved in building a small pond might be beyond financial reach of the farmer.
The impact of aquaculture on the environment varies by rate of intensity of the production system. According to ICLARM, even the more extensive aquaculture systems (where little or no feed or fertilizer inputs are used) may lead to the destruction of eco-systems, and pose health risks to workers from water borne diseases. Especially in integrated agriculture-aquaculture systems, toxic substances in livestock feeds (e.g. heavy metals, pesticides, or antibiotics) may accumulate in pond sediments and fish.
Intensive aquaculture systems, mainly reliant on external feed and fertilizer inputs, will have additional abusive effects because of pollution by effluents. Escapes of exotic modified, or genetically modified organisms on ecosystems may have an unpredictable impact as well.
Increased aquaculture productivity may lead to oversupply and declining world prices in specific markets. Shrimp trade is the most significant example. Shrimp trade amounts to over 20 per cent of world fishery trade, with more and more supplies coming from culture ventures. Main exporters are China, Taiwan, Thailand, Indonesia, and Malaysia. Shrimp breeding has recently also been taken up in India, Bangladesh, Sri Lanka, Ecuador, and Mexico.
Prices are likely to remain weak in the future, as shrimp farming is expanding enormously throughout developing countries.
1089 92 - 3/139
Review, book, semi-arid zones, case studies, agricultural engineering, crop production, tillage systms, dry farming, soil properties, soil erosion, management systems, tillage equipment, FAO
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