The issue is widely appreciated: rapidly growing populations in Asia increase the gap between supply and demand for fish, thereby threatening national food security in many countries. Furthermore, it is generally accepted that aquaculture has the greatest potential to bridge this gap as capture fisheries, though still the major fish source in most countries, are static or or in decline due to over-fishing and environmental degradation. It is generally agreed also that aquaculture should be both socially and environmentally sustainable.
The spectacular growth of shrimp culture over the past decade has "stolen the limelight" of aquaculture and diverted attention from addressing the crucial role of fish in food security in Asia. This was underlined at the World Aquaculture Symposium in Bangkok by contrasting attendance at sessions on shrimp culture with those on integrated farming: sessions of the former overflowed with people while those of the latter were practically deserted.
The matter is compounded further by the tendency of the public to equate aquaculture as a whole with intensive aquaculture and shrimp culture, and even more disturbing, of many aquaculture professionals and agencies involved in development.
This article aims to redress this imbalance. It outlines the role of fish in food security and questions whether the "blue revolution" in aquaculture has taken place. Both negative and positive contributions of aquaculture are discussed, with an airing of widespread misconceptions concerning the contributions of aquaculture to food security.
Coastal finfish and shellfish in some countries contribute to food security rather than generation of foreign exchange; abandoned shrimp ponds may also have potential for herbivorous tilapia culture affordable to the poor. Large-scale feedlot livestock/fish integrated systems and wastewater-fed finfish and aquatic vegetable systems in peri-urban areas also play a role. Here emphasis is given to small-scale inland aquaculture because of the magnitude of social and enviromnental problems in rural areas and its vast unfulfilled potential to contribute to food security.
Fish and food security
Staple crops such as rice and wheat are the major source of energy and total protein in most diets in Asia. Fish are also a staple in many countries and additionally have special nutritional characteristics to warrant consideration in food security. Pregnant and nursing mothers, infants and preschool children cannot obtain adequate nutrition from a mainly cereal- or tuber-based diet. Fish contain high amounts of protein with balanced amino acids, and are rich in certain vitamins and minerals. They also contain polyunsaturated fatty acids which are required in the development of the brain, and provide energy-dense fats for infants who may be unable to derive enough energy from a predominantly cereal-based diet.
Official fish consumption statistics reveal that insufficient fish are now eaten in many countries where fish is a traditional staple with rice. The annual average fish consumption in Asian developing countries has doubled from 5 to 10 kg per caput over the past three decades, probably due to growth of aquaculture. However, this is still far below the minimum requirement of 20 kg per caput annually estimated for a society where fish is an important dietary component of human nutritional needs. In Cambodia and Lao PDR fish consumption has declined by half over the past three decades and has remained static in Vietnam, probably due to the added constraints to overfishing and environmental degradation of war and civil unrest.
Need for a blue revolution
Reference is frequently made to a "blue revolution" analogous to the green revolution in agronomy. The green revolution addressed the problem of feeding the hungry in developing countries through increased production of staple crops such as rice and wheat. Many countries were able to eliminate cereal deficits, although not without some adverse social and environmental consequences. As there is an unresolved growing deficit of food fish in many developing countries for both poor producers (small-scale farm households) and poor consumers, the "blue revolution" in aquaculture has yet to take place.
It is not generally appreciated how few farmers culture fish, even in Asia. Global aquaculture production has been rising rapidly for the past two decades, and Asia produces almost 90% of the output. However, almost 80% of Asian production comes from East Asia, particularly China. South and Southeast Asia farm only about 9 and 13%, respectively. Probably fewer than 10% of small-scale farms in the region farm fish. Those that do mostly farm below potential, commensurate with their resources. Considerable promotion is required to intensify production of existing farmers and to facilitate new entrants to farm fish so that aquaculture can approach agronomy and animal husbandry as a major food producing activity.
Negative contribution to food security
Rather surprisingly, certain traditional and modem intensive aquaculture systems have a negative impact on food security. As both depend on nutritionally complete diets with significant amounts of fish, there is a net loss of protein in feed compared to that in cultured fish.
Culture of fish in cages in the lakes and rivers of Cambodia, Thailand and south Vietnam depends largely or entirely on small, wild fish. Although profitable, because of the price differential between high value food fish and low-value fish used for feed, their impact on food security wants study: culture of 1 kg of carnivorous food fish may require up to 5-6 kg of fresh wild fish for feed which are normally dried or fermented and used as food by poor people.
Modern intensive fish culture, including shrimp. depends on formulated feed that contains fish meal. A typical formulated diet containing 30 % protein fed to fish at a food conversion ratio of 1.5 leads to a 60% net protein loss in feed compared to fish. Declining capture fisheries have raised concerns that fish meal in formulated feed may actually constrain the growth of aquaculture.
Positive contribution to food security
Aquaculture has a significant positive contribution to food security through extensive and semi-intensive systems of production in which natural feed for fish predominates. In an extensive system there is no intentional addition of nutritional input for fish e.g., most rice/fish culture. In contrast, organic or inorganic fertilizers are added to stimulate increased production of natural feed in a semi-intensive system and/or natural feed is supplemented by feed such as vegetation, bran, or oil cake.
There are fundamental social and economic differences between extensive/semi-intensive and intensive systems of production which have relevance for food security. Nutritional inputs in semi-intensive production can be on-farm by-products; even when off-farm fertilizers and supplementary feeds are purchased, they are cheaper than formulated feed used in intensive systems.
Low cost inputs are affordable to poorer farmers and because the cost of production is low, the fish can be sold at a reasonable and affordable price to poor consumers. In contrast, fish cultured intensively can be marketed profitably only at a relatively high price because of the high production cost which puts them beyond the purchasing power of most consumers.
Several misconceptions constrain the promotion of extensive and semi-intensive aquaculture.
Perhaps the most common is that competition by aquaculture for land, water and inputs with agriculture has serious negative consequences. Competition there certainly is, but in an integrated system the outcome is more likely to be positive through synergism, i.e., increased output from use of a given resource.
There has been a recent marked surge in the construction of small on-farm ponds, mainly in response to increasingly unreliable availability of water. Such ponds, irrespective of whether they are used for aquaculture, have positive environmental impact. They essentially function as on-farm reservoirs and may serve as a focus for agricultural diversification, supporting the integrated production of crops and livestock as well as fish.
Integrated agriculture/aquaculture systems (IAAS) are often viewed as "closed" despite the export of large amounts of nutrients from the farm in produce. This is an ecological impossibility on a long term, sustainable basis. Early studies of Chinese integrated farms overlooked significant nutrient import onto the farm through off-farm purchase of human and livestock feed from sales of produce, including fish. These nutrients enter the IAAS in various ways, and are a major factor in its high level of productivity.
Aquaculture must satisfy rising farm household aspirations to be viable. Relatively low production from use of predominantly on-farm resources for subsistence may initially be socially relevant. However, when interest in aquaculture shifts to generate cash with development of the economy, the use of on-farm resources alone is insufficient. This is particularly true where opportunity costs of labor through alternative activities to aquaculture are high. This lesson was learned through over a decade's involvement by AIT and collaborating national institutions in the promotion of aquaculture, starting in Northeast Thailand, and extending to Cambodia, Lao PDR, and Vietnam over the last five years. A balanced strategy with judicious use of on-farm by-products and relatively cheap off-farm inputs is required to increase fish production to levels attractive to the farmer, thus addressing both social and environmental aspects of sustainability.
Finally, the crucial role of public sector, non-government organizations and donor support in promotion of small-scale aquaculture should be recognized. The private sector has demonstrated it can promote intensive aquaculture without external support. However, relatively poorly educated farmers with little to no prior knowledge of aquaculture usually require initial assistance to help them gain experience and confidence in what is for most, a new venture.