Cover Image
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.

The future of fish production

The future of the extractive fishing industry has become less and less promising. Almost all of the 200 world fisheries are dependent on a few commercial species that are being fully exploited. However, the seas contain 15 thousand species, 99% of which are not used commercially. Although it is usually impractical to envisage commercial exploitation of these noncommercial species, a different approach - such as using artisanal methods or multispecific commercial fishing systems - might be possible to maintain catch values (although probably not the volumes).

Even with such adjustments, however, it appears that extractive production will not be able to satisfy the growing need for seafood, particularly in developing countries. Despite declines in the production capacity of the fishing industry, worldwide consumption of fish has continued to grow and even accelerate, and this trend is not expected to change in the near future. There is widespread agreement that seafood contains some essential nutrients that are not present in land animals or plants, and that its unsaturated fats make it a healthy source of protein (by lowering cholesterol levels in the blood, etc.).

By the year 2000, the demand for fish products will probably increase by another 30 million tonnes. It will be difficult to meet this demand when production from most large-scale fisheries is reaching its limit or decreasing. Locally, some increases can be expected in artisanal fisheries. but these will not meet world demands.

The growth of aquaculture

During the last few years, mainly as a result of global trends and demands for seafood, large investments at international and national levels have been directed toward aquaculture, particularly in some (mostly developing) countries where conditions are favourable (adequate temperature, abundance of nutrients, and inexpensive labour and operating costs). About 12 million tonnes of seafood per year is produced through aquaculture, and the industry is growing at a rate of about 10% per year (Economist 1994b). Of this harvest, about 70% is finfish species, 25% is shellfish, and 5% is shrimp. Some of the most important species of finfish produced by aquaculture are carp, tilapia, salmon, and trout.

The “artificial” production of various sea species is introducing pro’ found changes in the economic structure of the fishing sector. Shrimp consumption is satisfied by a few Third World suppliers. Some countries, such as Ecuador and the Philippines, have become large producers because of their strategic location. In Ecuador, the value of shrimp exports to the United States, Canada, and other countries increased from $56.8 million in 1980 to $491.3 million in 1991. In 1993, 150 thousand people were involved in catching shrimp larvae and in shrimp farming; this is several times the number of people involved in artisanal (50 thousand) or industrial fisheries (2 600).

Aquaculture may have a strong impact on the aquatic environment; for example, water is contaminated by organic matter and food chains are disturbed. Increased aquaculture activity may also affect aquatic ecosystems by adding to existing overfishing and contamination problems. Meeting world demands for seafood through aquaculture will mean increasing annual production from 12 million tonnes to 35 or 40 million tonnes in 6 or 7 years. This may be very stressful for the ecosystems where aquaculture is carried out and may be unsustainable in the medium and long terms.

Protecting diversity and sustainable production

The future of aquatic ecosystems will ultimately depend on the sustainability of production strategies. Natural aquatic ecosystems, like any other natural system, can be exploited for a long period only by carefully controlled methods that do not affect stock levels and biodiversity in the systems. If adequate controls are not enforced, worldwide demands for fish will not be met and continued degradation of aquatic ecosystems can be expected. However, rational management strategies, such as the promotion of local artisanal fisheries rather than large-scale, monospecific commercial fishing or diversification of consumption, may lead to sustained production and even some increases.

Substantial expansion of aquaculture activities will be necessary to keep up with the growth in demand for its products. If aquaculture strategies are based on conservation of natural environments, the biodiversity of ecosystems, and stocks, aquaculture may become another effective tool for feeding the population of the world without diminishing the value of its systems.

Management of estuarine environments

About 150 million people live on or near estuarine bodies of water on five continents. In North America, major estuaries are associated with the St Lawrence and Hudson rivers; in South America, the Rio de la Plata (see box 5), the Guayas in Ecuador, the Amazon estuary in Brazil, and the Orinoco in Venezuela. In Africa, because there are few well-developed coastal plains, estuaries are rare; only the Senegal, Congo, and Niger rivers have large estuarine ecosystems near their outlets to the Atlantic Ocean. In Asia, important estuaries occur in China (the Yangtze and Yellow rivers), India (the Ganges), and Indochina (the Mekong).

Estuarine regions represent the outlet of agricultural, fishing, commercial, and navigation activities in extensive areas far greater than the estuaries themselves. Even when they remain undisturbed by human activity, estuaries are fragile environments, experiencing frequent changes in salinity, sediment load, nutrient levels, and other physico-chemical characteristics. When human influence is added to the equation, the fragility of the ecosystems increases, and degradation can result in irreversible loss of production potential and biodiversity.

Because of their complexity and the continuous changes they experience, estuarine ecosystems require a much more careful and thoughtful management approach than other larger or more stable bodies of water. Although these systems occupy an important geographic “niche” in populated areas, no specific methods have been developed to address the issue of their sustainable management. The main elements to be considered are the following:

· The pattern of normal changes that takes place on a regular basis as a result of the interaction of the coastal and fluvial regimes;

· Periodic, catastrophic natural events, such as floods, hurricanes, unusually high tides, abrupt changes in salinity, or extreme variations in sediment load; and

· Anthropogenic influences, such as contamination, fishing, infrastructure in coastal areas, and changes in neighbouring basins.

In addition to these physical and biological factors, estuarine management is also limited by social, economic, political, and cultural elements that can also affect the human environment in which management decisions must be made. To address the issue properly, it is necessary both to gather the necessary scientific and traditional knowledge and to develop an adequate method for formulating and implementing appropriate policies and strategies.

5. The case of Rio de la Plata

The Rio de la Plata ecosystem is typical of the world’s estuarine environments. The widest estuarine body in Latin America, it sustains a broad spectrum of valuable species, some of which are unique. Fish found in the typical estuarine zone are croaker (or corvina), Hounder, flatfish, lacha, lisa (Mugil platanus and M. brasiliensis), white pargo, merluzas (Merluccius merluccius), and brotola (Urophycis brasiliensis). In the freshwater environment, species include sabalos (Prochilodus lineatus), bagre (Thamdia sapo and Pimehdus clarias), surubi (Psuedophtystoma spp.), dorado (Salminus maxillosus), and pate’ (Luciopimehdus pati).

The Rio de la Plata coastal zones are fished on a regular basis by several communities, mainly for hake and croaker. Hake, squid, tuna, anchovy, and several other species are obtained in deep waters, where the estuarine influence is less important, by commercial fleets owned by many small, medium, and a few large enterprises.

Croakers, which are among the most important commercial species in the Rio de la Plata region, are mainly found in the heart of the estuarine zone near Montevideo. They are exploited by artisanal fishermen and the coastal commercial fleet. In 1992, 25 thousand tonnes of croaker was harvested.

The main fishing communities are located in Pajas Blancas, Puerto del Buceo, and San Luis. The commercial fleets are based in the ports of Montevideo and Buenos Aires. Currently, 20 thousand people are employed directly or indirectly in the estuarine fishing industry in both countries. Commercial fishing is geared toward export markets, whereas artisanal fisheries satisfy local consumption.

Recent developments in the Rio de la Plata highlight the fragility of the estuarine ecosystem. First, episodes of widespread fish mortality are becoming more common in the region; millions of fish die for no apparent reason. Second, contamination from coastal sources seems to be increasing. At least 15 million people and 50 thousand industries are located along the shores; more than half the industries emit polluting effluent into the environment and practically no waste treatment is available. This pollution is worsened by the outflow of fluvial water loaded with sediment, fertilizers, and pesticides from the farming areas surrounding Montevideo and, to a lesser degree, Buenos Aires.

The outflow of these contaminants, together with overfishing or inadequate fishing practices, may jeopardize the sustainability of the estuarine resources, along with the viability of the artisanal and commercial fisheries. An unwanted by-product of the contamination process may be a decline in the quaky of the fish, which may affect the health of the fish-consuming population.