|Diversity, Globalization, and the Ways of Nature (IDRC, 1995, 234 p.)|
|6. Aquatic ecosystems|
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 worlds 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.