Aquaculture – the farming of fish, shrimp, shellfish, and seaweeds – has been a source of human protein for nearly 4,000 years, especially in Asia . Unprecedented growth in aquaculture production in the last decade, however, has given it increased importance in the modern food supply. From 1984 to 1994, world aquaculture production more than doubled, making it one of the fastest-growing food production activities .
Globally, almost 20 percent of all fish and shellfish production in 1995 was attributable to aquaculture, or about 21 million metric tons (not counting seaweeds) out of 112 million metric tons . (See Farmed Fish Are a Growing Share of the Global Fish Harvest.) Yet this industry’s contribution to the human diet is actually greater than the numbers imply. Whereas one third of the conventional fish catch is used to make fishmeal and fish oil, virtually all farmed fish are used as human food. Today, one fourth of the fish consumed by humans is the product of aquaculture, and that percentage will only increase as aquaculture expands and the world’s conventional fish catch from oceans and lakes continues to decline because of overfishing and environmental damage . As currently practiced, however, aquaculture also causes environmental damage, raising questions about how best to meet food demands and preserve environmental quality.
|Farmed fish area growing share of the global fish harvest|
|Aquaculture production as a share of total marine and freshwater fish harvest, 1984-95|
|Source: Food and Agriculture Organization of the United Nations (FAO), The State of the World Fisheries and Aquaculture, 1996 (FAO, Rome, 1997), Table 1, p.5.
Note: Includes finfish and shellfish only; does not include seaweed.
Asia dominates world aquaculture, producing four fifths of all farmed fish, shrimp, and shellfish . China is by far the leading producer, contributing nearly 60 percent of 1994 world production, or some 15 million metric tons . Indeed, aquaculture accounts for more than half of China’s total fish production each year. India is the second largest producer, with 9 percent of the world’s aquaculture total in 1994 ). (See China Dominates World Aquaculture.)
Aquaculture products fall into two distinct groups: high-valued species such as shrimp and salmon that are frequently grown for export, and lower-valued species such as carp and tilapia that are consumed primarily locally. China, for instance, raises a substantial amount of shrimp in intensively managed ponds along its coastline for the lucrative export trade . Yet China’s total aquaculture production is dominated not by shrimp but by carp raised in relatively low-tech inland ponds for local consumption. The four major carp species – silver carp, grass carp, common carp, and bighead carp – account for more than one third of world aquaculture production – nearly all of it in China .
These carp are raised primarily as a supplementary activity to regular crop agriculture on Chinese farms. Carp are herbivores and can survive on low-cost, readily available feed material, rather than on the high-cost fishmeal that carnivorous species such as shrimp and salmon require to grow; thus carp farming is both more economical and easier to integrate with other conventional farm activities than are other types of aquaculture. Whereas farmed shrimp tend to grace the tables of consumers in high-income regions like Japan, Europe, and the United States, carp make a direct, significant contribution to the protein needs of less affluent rural Chinese .
Can continued expansion of aquaculture increase the global fish catch enough to feed the world’s growing need for fish protein? Certainly, some growth in world aquaculture can be expected, but just how much is not clear. One analysis projects that, under favorable conditions, global production could nearly double by 2010 to 39 million metric tons. Several factors are pushing this growth in both intensive aquaculture and in small-scale, farm-based efforts. Global demand for fish is rising even as many ocean stocks are declining, and aquaculture techniques and technology continue to improve. In addition, small-scale aquaculture offers farmers a ready source of both subsistence food and cash, and these benefits are likely to promote expansion beyond its traditional stronghold in Asia .
However, there are also serious constraints on aquaculture’s future growth. For one, fish farming requires both land and water-two resources already in short supply in many areas. In Thailand both these resources have been diverted in recent years to fuel the growth of the aquaculture industry. For example, nearly half the land now used for shrimp ponds in Thailand was formerly used for rice paddies; in addition, water diversion for shrimp ponds has lowered groundwater levels noticeably in some coastal areas. In China, the concern over loss of arable land has led to restrictions on any further conversion of farmland to aquaculture ponds .
References and notes
1. George K. Iwama, “Interactions between Aquaculture and the Environment,” Critical Reviews in Environmental Control,Vol. 21, No. 2 (1991), pp. 177-216.
2. Food and Agriculture Organization of the United Nations (FAO), The State of World Fisheries and Aquaculture, 1996 (FAO, Rome, 1997), p. 11.
3. Ibid., p. 5, Table 1.
4. Op. cit. 2, pp. 4-5.
5. Op. cit. 2, p. 12, Figure 12.
6. Op. cit. 2, p. 59.
7. Op. cit. 2, pp. 11-13; p. 14, Figure 14.
8. Biksham Gujja and Andrea Finger-Stich, “What Price Prawn? Shrimp Aquaculture’s Impact in Asia,” Environment, Vol. 38, No. 7 (1996), pp. 12-14, 33.
9. Op. cit. 2, pp. 11-12.
10. Op. cit. 2, p. 59.
11. Bob Holmes, “Blue Revolutionaries,” New Scientist (December 7, 1996), p. 34.
12. Op. cit. 2, pp. 24-25.
13. Op. cit. 11, pp. 35-36.