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close this bookDiversity, Globalization, and the Ways of Nature (IDRC, 1995, 234 p.)
close this folder6. Aquatic ecosystems
View the documentExtractive exploitation
View the documentThe future of fish production

Extractive exploitation

Aquatic ecosystems have provided food and other resources to various cultures for a very long time. For many societies, fish and other aquatic organisms are still a main source of food and income. Exploitation of aquatic ecosystems has been largely through extractive methods, mainly because these systems are much harder to manage than such closed systems as agriculture or livestock farming. In fact, it is difficult even to establish ownership of water resources.

One cannot routinely “fence” portions of water to keep target species within a limited area as is normally done on land. In oceans and open-sea environments, accurate locations are difficult to establish. Ever, in large lakes and rivers, it is seldom possible to keep an exploited species within a limited area or prevent others from catching it. Only in small lakes or streams or shallow coastal waters (especially bays, estuaries, and tidal zones) can ecosystems be controlled in any way.

There are cases, however - such as in Japan and other east Asian countries - where aquatic resource management is based on community use and claims are recognized by neighbouring communities. In these countries, fishing areas are often fenced off. Exploitation of controlled or artificial aquatic ecosystems has been an important activity since ancient times. Some agricultural systems in Asia (south China, for example) include intensive fish farming in carefully managed ponds. This type of aquaculture is frequently associated with rice production, which also requires careful management of water. Other areas of the world where the practice has been important include the Philippines and India.

Early fishing methods did not result in a significant reduction of fish stocks; thus, large aquatic ecosystems remained virtually unchanged by extractive activities. About the end of the 19th century, however, this situation changed dramatically when large fleets began fishing on an extensive scale in the more productive areas of the world.

Productivity of aquatic ecosystems is limited mainly by the amount of dissolved oxygen and some key nutrients, such as phosphorus and nitrogen. Oxygen concentration depends largely on the temperature of the water; higher levels are found in low-temperature environments. The more important nutrients in oceans and seas are carried from the adjacent continent by rivers, underwater streams, etc., or from the sea bottom through the upwelling of deeper, cooler waters. Finally, solar radiation contributes to productivity in aquatic ecosystems by increasing the potential for photosynthesis and primary production. This combination of factors is found on the Pacific coast of South America, in the northwestern Pacific, and on the Grand Banks in the North Atlantic, for example.

Recent improvements in fishing methods, including the widespread use of trawlers, draggers, spotter planes and helicopters, and directional radar to locate large schools of fish precisely, have made sustainable management of fish stocks difficult. In addition, fishing fleets from several countries have converged on the more accessible fishing zones, resulting in overfishing and subsequent decreases in the annual catch. Now, a vessel can tend up to four inexpensive nylon filament nets instead of one and freezing chambers can store hundreds of tonnes of fish, allowing the fleets to deplete large areas in a short time.

Agreements and controls have come too late; they are insufficient and not respected. Even with controls, fishermen frequently find ways to catch what they can before someone else does. Small fish of the target species are discarded because fishermen want the best price for their allowed quotas. Other species are also thrown away even though other fishermen might be interested in them. It is practically impossible to patrol all areas of the seas, and illegal nets are easy to hide. The result is widespread overfishing, far beyond the defined limits of sustainability. Many of the largest stocks of fish, such as those in the South American Pacific and the North Atlantic, have been exploited beyond their replacement potential. In 1990 and 1991, the Food and Agriculture Organization reported that the world catch had begun to decrease. “Fishermen are living off capital, consuming the resource that should yield their catch” (Economist 1994b).

The Peruvian fisheries

In Peruvian coastal waters, the main species sought was the Peruvian anchovy. To a large extent, exploitation of this species was a result of extensive fishing by newly formed Peruvian fishing companies or concessions awarded by the Peruvian government to foreign fishing fleets from Japan, Russia, and Poland, among others. The annual catch increased quickly, reaching a maximum of 13 million tonnes in 1970. In 1973, a crisis occurred, and the volume of the catch dropped to less than 2 million tonnes. Since then, it has remained below 5 million tonnes (Table 3).

North Atlantic fisheries

In the North Atlantic, large-scale fishing was concentrated in the North Sea, along the Norwegian coast, in the coastal areas of Iceland and Greenland, and on the Grand Banks off the North American coast. These fisheries are based mainly on cod, herring, and other species that are not for human consumption, such as Norway pout, capelin, blue whiting, and sand eels. Overfishing caused a decrease in cod and herring catches beginning in the late 1960s and continuing through the 1970s. The large cod catches of about 3.3 million tonnes in 1970 plummeted

Table 3. World production of main commercial fish species.


Production (tonnes per year)


Alaska pollack


N Pacific

Yellowfin tuna


Pacific, Atlantic, and Indian oceans

Club mackerel



Peruvian anchovy


SE Pacific

South American pilchard


SE Pacific

Chilean jack mackerel


SE Pacific

Atlantic cod


N Atlantic

Atlantic herring


N Atlantic

European pilchard





NE Atlantic

Japanese pilchard


NW Pacific

Skipjack tuna


Pacific and Indian oceans

Source: Economist (1994b). to 2.2 million tonnes by 1978. Herring yields dropped to 0.8 million tonnes in 1978 from 2.6 million tonnes in 1970. The trend continued unabated throughout the 1980s, resulting in the current critical situation that forced governments to ban fishing in some of the main fisheries, such as the Grand Banks (see box 4).

4. The Grand Banks

Located on a shallow continental shelf, the Grand Bank receive a rich supply of nutrients and oxygen in the cold Labrador current. This area contains one of the largest fish stocks of the Atlantic Ocean, and fleets from all over the world have been fishing here regularly for centuries. The intensive harvest, mainly of cod, increased in the 1960s. In 1968, vessels from West Germany, the Soviet Union, Spain, and several other fishing countries, as well as Canada, were trawling in the area for cod and other commercial species. The total catch obtained from the Grand Banks was nearly 1 million tonnes of fish per year.

After 1977, activity decreased somewhat with the extension of the territorial waters and economic zone claimed by Canada and the United States to 200 miles (320 kilometres) from the coast. However, international exploitation beyond that boundary continued. In addition, French fishing fleets regularly visited the area by taking advantage of the French jurisdiction around the islands of Saint Pierre and Miquelon in the Gulf of St Lawrence.

During the 1970s and early 1980s, fishing by Canadian and American boats was still intense. In Canada, fishing plants were established and fishers were encouraged to buy bigger boats; even the government set up two off-shore trawling operations. Along with the competition from US and French fishers, cod resources were nearly depleted.

Other factors also played a role, such as the suspension of the seal hunt, which dramatically increased the number of seals feeding on fish. In any case, the equilibrium of the ecosystem was upset by human intervention, with serious social, economic, and environmental implications.

Other world fisheries

The north Pacific is also an important fishing area. The continental shelves are narrow, but catches of pelagic species - mackerel, anchovy, sardine, and herring - are large. The annual harvest in this area reached a maximum of 22 million tonnes, mainly from the northwestern sector.

The main countries fishing in the north Pacific are Japan, China, and, to a lesser degree, Canada, United States, Russia, and North and South Korea. Japan has more than 1 500 fishing ports, and the total annual catch exceeds 10 million tonnes, of which about 20% comes from coastal fisheries. About half of the protein in the Japanese diet is derived from fish.

The Sea of Okhotsk fisheries have been exploited intensively for several decades, especially for pollack, the most important commercial fish in the region (Bird 1993). Traditionally, Russia and Japan have been the primary countries fishing in the Okhotsk. Currently, pollack stocks are seriously threatened. The fish is now unavailable, even where it was a traditional food, such as in the Russian cities of the Far East.

Overfishing has occurred because of a lack of control. Only very low catches have been reported to the Pacific Ocean Research Institute for Fisheries and Oceanography. At a meeting in Vladivostok in September 1993, requests for a moratorium from Russia, Japan, and the United States were “ejected by the Polish and South Korean delegations. It is widely believed, however, that the main cause of the depleted stock is overfishing by the “joint ventures” established between Russian and foreign enterprises.

Growth in the world’s fisheries has stopped. From 1950 to 1988, the annual growth in fish catches was 4%. In the following 4 years (1988-1992), it fell at a rate of 0.8% per year (Brown 1993).

The decrease in catches was partly offset by the opening of new fisheries, such as those in the southern Atlantic. The growth or persistence of artisanal fisheries, which are much less devastating than factory fishing fleets, has also helped to stabilize production figures.

Today, world production stands at 87 million tonnes per year (World Bank et al. 1993); another 13 million tonnes per year is contributed by aquaculture, bringing the annual total to about 100 million tonnes. Of this harvest, about 70% is consumed by people and about 30% is used for oil extraction and animal feed. Demand is continuing to grow, but natural fisheries are nearing their limits of sustainability. Catches in the main fisheries will continue to decrease. Even in the face of disaster, however, greed may impel some to further expand fishing activities until they become uneconomic or until global awareness of the problem forces the implementation of appropriate controls.

Overfishing is not the only problem affecting aquatic ecosystems. Water quality in the oceans is affected by polluted influxes from coastal, industrial, urban, and farming areas. As a result, in some coastal zones, important fish stocks have been reduced or eliminated by pollution and habitat degradation, and others cannot be consumed safely because of the concentration of contaminants in their tissues.

In some coastal countries, marine pollution has become a nightmare. This is the case in most of the Mediterranean Sea, where a continuous outflow of wastewater effluent and spills has drastically damaged the natural ecosystems of the Adriatic and Ligurian seas and the eastern and western edges of the Mediterranean. Other marine environments where pollution is seriously affecting the aquatic ecosystems include the Black Sea, the North Sea, the northwestern Atlantic, the Japan Sea, the China Sea, the Persian Gulf, and the Red Sea. In the coastal areas of Florida, the ecosystem is close to collapse as a result of repeated algal blooms, which are systematically affecting local fish hatcheries (Dewar 1993). Similar phenomena have been observed in Malaysia and Brazil. Undoubtedly, the rapidly spreading degradation of oceanic and marine water bodies is a new and increasingly important factor contributing to the worldwide decline in fish populations.