Sir

If agriculture were to arise today, knowing what we do about its impacts on the natural environment, biodiversity and poverty, it would probably encounter the same mixed reception as aquaculture. R. L. Naylor et al.1 give an excellent overview of the serious challenges facing aquaculture. As they show, in some cases it actually reduces fish supplies for human consumption.

Naylor et al. list four main goals for the industry: more farming of fish at low trophic levels (low on the food chain); reduction of fish meal and fish oil inputs in feed; development of integrated farming systems; and promotion of environmentally sound practices.

After 23 years of aquaculture research in Asia, Africa and the Pacific, the International Centre for Living Aquatic Resources Management (ICLARM) strongly supports these goals and adds a fifth: access for poor consumers and small-scale producers. Leasing and community organization can allow even landless people to become fish farmers and conduct profitable micro-enterprises if aid is well-targeted.

Non-government agencies are carrying out many such projects in countries such as Bangladesh, where fish can be up to 80% of animal protein consumed. They farm various species of carp (most importantly Catla catla, Labeo rohita and Cirrhinus mrigal), catfish (Clarius spp.)and tilapia (Oreochromis niloticus), which require low input levels. In the Pacific, we are showing the potential for farming giant clams (Tridacna spp.), blacklip pearl oysters (Pinctada margaritifera), hard and soft corals and tropical marine aquarium fish, and for restocking and enhancing the sea cucumber Holothuria scabra.

Small island developing states rely on marine resources for their income. French Polynesia and the Cook Islands, for example, use environmentally friendly aquaculture to rear blacklip pearl oysters, which are low on the food chain and — producing prized black pearls — are second only to tourism for bringing in foreign exchange. The value of the black pearl harvest in French Polynesia in 1999 was US$200 million. Demand for cultured giant clams, and hard and soft corals, is increasing, and these can be grown on coral reefs with apparently no adverse impact. All these species and systems have been selected either for accessibility to poorer people, for environmental sustainability, or to supply products that are used locally.

Rising prices mean that fish must be cheap to produce, such as carp and tilapia, or poorer consumers will not benefit. M. Dey et al.2 show that adopting the improved strain of Nile tilapia will reduce tilapia price by 5–16% in Bangladesh, China, the Philippines, Thailand and Vietnam. Poorer consumers will benefit most in all these countries except the Philippines.

Aquaculture can also restock high-value coral-reef species that have been severely depleted by over-fishing. In the small islands of the Pacific, research has paved the way for inshore marine resources to provide substantial income for coastal communities. Methods have been developed for culturing sea cucumbers, giant clams, trochus and green snail, and the emphasis of research is now on how best to release juveniles into the wild.

Release of cultured juveniles can also overcome the widespread problem of too few young fish returning to settle in the fishery area. Such practices have been used for 90 species in Japan over the past 30 years, particularly successfully in the case of the scallop.

Aquaculture and stock enhancement are still in their infancy, and some mistakes have been made in their development. New directions should follow the guidance outlined by Naylor et al.; they should also heed the questions of access by poorer societies and proceed wisely with stock enhancement under suitably safeguarded conditions.