Chapter 6: Fisheries
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6.2 Historical developments and present situation
6.3 Prospects for the future: production
6.4 Implications for consumption
6.5 Major policy issues for the future
The world's fishery resources are an important source of protein as well as employment and economic revenue. The historical developments as well as the future prospects of the sector are conditioned, to a significant extent, by the wild characteristic of the resource and the fact that, for most species, the levels of production are limited by nature. This has three important consequences. First, beyond certain levels, additional investment in fishing effort does not produce additional yields and, in many cases, actually leads to declines in total catch as well as to economic waste. Such an increase in fishing effort is inevitable in those, almost universal, situations where there is ineffective fisheries management. Second, with growing demand and limited supplies, the real prices of fish products inevitably increase. This has important and damaging consequences for low income consumers, particularly those from the developing countries. The third major, and more positive, result is that limited natural supplies and high prices serve to stimulate increased production through the cultivation of those species that allow it.
The potential for increasing total production much above present levels is rather limited. Attaining and maintaining these somewhat higher levels will depend on greatly improved management of the fishery resources. Without such improvements, there is a risk that even present levels may not be maintained. Under the circumstances, the prospects are that the real price of many species of fish, particularly those used for direct human consumption, will continue to rise. Better management would, therefore, contribute to containing such price increases in the longer term, and to reducing or eliminating economic inefficiencies believed to be widespread in fishing operations at present.' Improved management of capture fisheries may, at least in the short term, lead to a lower volume of production, albeit of better quality. Eventually, the overall production constraints may be somewhat relaxed by further growth of aquaculture and stock enhancement programmes such as culture-based fisheries.
6.2 Historical developments and present situation
Since the 1600s, the principle of the freedom of the seas dominated the use of the oceans and their resources. Beyond narrow limits of national jurisdiction (3-12 miles), the resources were open to all comers. With declining catches per vessel in the traditional grounds, the fishermen either moved to new areas or adopted more intensive techniques. In more recent years, the pace of exploration and exploitation was expedited by the development of automotive power, synthetic fibres in nets and refrigeration equipment.
This pattern had three consequences: one was the generalized depletion of conventional stocks; a second was the global extension of fishing effort to new, less conventional species as well as to far distant waters; the third was the increase in conflict between the local fishermen of the coastal states and the distant water fishermen from foreign states fishing close to shore. This stimulated increasing claims by coastal states to extended jurisdiction.
The major maritime powers generally succeeded in maintaining the principle of the Freedom of the Seas, which benefited their military and fishery interests, during the First and Second United Nations Conferences on the Law of the Sea (in 1958 and 1960). But the pressure for extended jurisdiction was inexorable and, while the discussions at the Third UN Conference were still under way in the 1970s, a regime of a 200 mile extended fisheries zone was established, resulting in a redistribution of the seas' wealth.
The choice of 200 miles, however, has no relevance to the habits of fish. Some species (e.g. oyster, clams) are sedentary while others (e.g. tuna, salmon) swim vast distances and are found both inside and outside a 200 mile limit. Given the wide diversity of the resource, there is also no direct connection between the size of a fisheries zone and wealth of resources. Among the most fertile areas are the continental shelves rich in demersal stocks (groundfish such as cod and haddock) and the upwelling currents inhabited by pelagic species (those feeding on the surface such as herrings and sardines). Temperate zone waters tend to contain relatively large populations of few individual species; while outside upwelling areas (e.g. Peru), tropical waters have large numbers of species and small populations of each. In the open ocean, the stocks are diffused. Some high seas species have schooling habits but require high search costs for their location. Others seldom aggregate and can only be taken by gear that filters great quantities of water.
Volume and species composition
Since the 1950s total world production of fish increased at a rate of about 6 percent per year until the collapse of the Peruvian anchoveta fishery in the early 1970s. After that setback, with some minor fluctuations, production continued to grow reaching the peak of 100 million tonnes in 1989. However, the overall growth rate declined to 2.5 percent per annum (Figure 6.1). World production fell to 97 million tonnes in 1990 and has remained at that level for both 1991 and 1992. It has been characteristic of these developments that the contribution of some (notably) traditionally high value species to the total catch and that of other less traditional species has declined, while the catch of predominantly high volume, low unit value species has been subject to wide fluctuations. For example, a significant part of the growth during the past two decades was due to the increase in the catch of a single species, Alaska pollack, whose catch accounts for some 5 percent of world fish production. Another large part of the increase came from a few species of small shoaling pelagic fish. After the collapse of the Peruvian anchoveta, the total catch of this group fell to 6.3 million tonnes in 1973, down from 16.7 million tonnes in 1970. By 1980, the small pelagic global catch was back up to 13.2 million tonnes and peaked at 21.3 million tonnes in 1989, making up about 20 percent of total world production. Most notable were the increases in Japanese pilchard, South American pilchard and Chilean jack mackerel. These kinds of species are subject to very wide fluctuations in abundance which are generally cyclical in nature and result from natural environmental changes. Experience has shown that heavy fishing can significantly impede their recovery. The composition of current world production by major species is shown in Figure 6.2.
During the past two decades, the catch of a large number of demersal stocks (e.g. Atlantic cod, Cape hakes, saithe, haddock, Atlantic redfishes) has declined significantly, due largely to continued, heavy overfishing. Although there are instances of stock rehabilitation through the adoption of conservation measures, these are relatively scarce in most areas of the world. In contrast, production of oceanic pelagics (e.g. tunas), cephalopods and other shellfish has shown a steady increase.
While marine catch has successively decreased from the peak year in 1989 (86.4 million tonnes), the production of inland species rose dramatically during the 1980s, to 15 million tonnes in 1991 (15 percent of total production). Most of this is accounted for by nine major species whose catch was less than 500 000 tonnes in 1970 but over 5.5 million tonnes in 1990. As noted later, these species are produced almost entirely by aquaculture and most of the growth occurred in China.
A significant aspect of these developments is the change in the value of catch. Except for the tunas, the species whose catch has been growing are relatively low priced. Most of the shoaling pelagics, for example, are caught for reduction into fishmeal. On the contrary, the species whose catch has been falling are mostly high valued. The net result is that the increase in total quantity of catch has not been matched by a commensurate increase in economic value. Overfishing of the high-valued stocks has led to their depletion and, with decreased supplies, to price increases. This pattern will eventually occur for most species which are not readily cultivable. Table 6.1 presents a qualitative overview of the main characteristics of the different market segments and species.
The dominance of a few countries
It is significant that a very few countries have an extraordinary influence on total world production. The effectiveness (or lack of effectiveness) of management regimes to which the fishery operations of these countries are subjected can have a major impact on global production. Twenty countries accounted for 80 percent of total world output in 1991 and six of them made up more than 50 percent (Figure 6.3). The concentration by countries and that by species are related to each other. For the three major developed countries, most of the increases were due to two species: Alaska pollack and Japanese pilchard. There has been an even greater dominance of individual species in the catch of two of the three major developing countries. For Peru, 90 percent of the catch in 1990 was from anchoveta and South American pilchard. For Chile, 81 percent was from those two species and Chilean jack mackerel. These are all low valued species whose abundance tends to fluctuate widely.
The development of aquaculture
During the 1980s, there was a rapid growth in the development of aquaculture. Between 1984 (when FAO began recording aquaculture production) and 1990, total production from aquaculture roughly doubled reaching about 12 million tonnes (excluding seaweeds). This has had two main thrusts: one in China and the other, more globally, for certain high-valued species.
China's aquaculture output increased about 2.5 times from 1984 to 1990, accounting for roughly 45 percent of total world aquaculture production in the latter year. To a large extent this is made up of various species of carp often raised in conjunction with agriculture since a long time ago. There have also been large increases in the culture of shrimp and mussels; to the point where China produces about 27 percent of global production of shrimp from aquaculture and about 38 percent of global production of mussels.
A separate development has been the rapid increase in output of salmon, shrimp and various shellfish to meet the demand of the luxury market in developed countries. Currently, farmed salmon makes up about 25 percent of total world salmon production from all sources and farmed shrimp about 24 percent of total shrimp production. In both cases, aquaculture output has been sufficient to significantly affect world prices. Oysters have always been cultivated and there has not been much growth in production in recent years. But there has been a large increase in farming of other shellfish since 1984. Both mussels and clams have increased about 60 percent while scallops have grown by over 300 percent.
Patterns of consumption and trade
Over the past few decades, production of fish for human use has grown more rapidly than population with a resulting increase in per caput consumption. The relevant data are shown in Table 6.2. While fish provide a relatively minor source of dietary energy supplies (accounting on average for 17 calories out of 2475 in the developing countries), they are an important source of essential fatty acids, vitamins and minerals. However, although a handful of countries tend to dominate global production of fish, many countries depend heavily upon fish as a major source of protein. For the developing countries as a whole, fish currently make up about 19 percent of total animal protein consumption, or just over 4 percent of protein from both animal and plant origin. However, this latter share is very high in some countries, both developed (e.g. Japan, Norway, Portugal) and developing ones (mostly in East Asia, e.g. Philippines, Thailand, and Africa, e.g. Congo, Angola, Ghana, etc.); and it is very low in others (e.g. Argentina, many land-locked countries in Africa).
Table 6.1 Characteristics of major market segments for fishery products
|Market||Types of species||Sources||Prices (ex-vessel)||Implications|
|Luxury||Salmon, shrimp, sea bream, etc.||Capture and culture||$3-4/kg. Tending to decline with increased cultivation||Increased trade from culture countries. Increased demand for fishmeal. Conflicts over space and water use|
|Flatfish (flounder, sole, etc.)||Capture||$3-4/kg. Increasing due to depletion of stocks||Most stocks heavily over-plaice, fished. Incentive for culture|
|Tuna||Capture||$1.50-2.00/kg. Reaching limit because of substitutes (e.g. chicken)||High consumption in developed countries. Increased processing in, and exports from, developing countries|
|Crabs and lobsters||Capture and production of substitutes from low priced fish through surimi process||$3-12/kg. Tending to decline with production of substitutes|
|Molluscs (oysters, clams, cockles, mussels)||Mostly culture, some capture||$1-5/kg. May decline for cockles and mussels with increased culture||Opportunities for increased production and consumption in developing countries. Sanitation problems|
|Cephalopods (squid, octopus and cuttlefish)||Capture||$1-4/kg. Likely increases over the long run||Opportunities for increased capture by some developing states and for increased exports. Healthy food merits|
|Standard||Most finfish species making up the bulk of the market (cod, hake, haddock, jack, mackerel, grouper, croaker, etc.)||Capture||$0.50-3.00/kg. Increasing due to depletion of stocks.||Generally heavily overfished with declining total catches and decline in size of animals|
|Low income||Carp, catfish, milkfish, etc||Culture||$0.20-1.00/kg||Heavy production in Asia, mostly China. Very little in Africa and Latin America|
|Artisanal-caught marine and lake fish (sardines, mullet, scad, tilapia, chub, mackerel, etc.)||Capture from canoes, rafts and other small craft, generally non-powered||$0.20-1.00/kg. Rising prices due to depletion||Generally heavily overfished with declining total catches and decline in size of animals|
|Frozen blocks of low quality fish of miscellaneous species||Capture by industrial vessels of former USSR||Under $1/kg||Sold to local African coastal states for various reasons. Not likely to continue for long|
|Trawler by-catch (small individuals including juveniles of high-valued species)||Discards from shrimp trawling operations||$0.05-0.50/kg. Prices increasing as discards sought for feed to use in aquaculture||Locally an important source of protein for low-income consumers|
|Non-food markets||Small shoaling pelagics. (anchovetas, pilchards, sardinellas, etc.) reduced to fishmeal and oil, mostly for feed||Capture mostly by large-scale operations||$0. 10-0.40/kg. Price increases presently limited by price of substitutes for feed (e.g. soybeans)||Conversion to food use possible in future but stocks not found in Asian waters where future need will be greatest|
Trends in trade in fishery products closely reflect changes in production and technology development. The expansion of international trade in fish and fishery products has exceeded the growth in world fish production. World fish trade, estimated at 32 percent of world production (24 million tonnes) in 1980, increased to 38 percent in 1990 (37 million tonnes). A significant part of this increase was from increased exports of fresh and frozen products (3.3 million tonnes to 6.0 million tonnes product weight). Other large increases in exports included those of shrimp, which increased from 0.4 million tonnes to almost 1.0 million tonnes, and of fishmeal which rose from 2.0 million tonnes to 3.2 million tonnes, although with significant fluctuations in volume during the period.
Table 6.2 Fish: historical data of food and non-food use
|A. Food (liveweight equiv.) Per caput (kg)|
|Near East/North Africa||2.7||4.5||5.3|
|Latin America + Carib.||6.6||9.0||8.5|
|East Europe + FSU||19.3||20.8||21.0|
|Total (mill. tonnes)|
|Near East/North Africa||0.5||1.0||1.6|
|East Europe + FSU||6.4||7.5||8.2|
|B. Fishmeal (liveweight equiv.)|
|World totals (mill. tonnes)||19.7||19.5||27.8|
|Total fish use||60.1||71.3||98.2|
The increase in trade has been particularly marked in value terms, exports reaching a total of US$38 billion in 1991 compared with US$15 billion in 1980. The share of the developing countries in total trade has grown slowly but steadily to some 47 percent of total exports in 1989. Exports of shrimp, cephalopods, tuna (both frozen and canned) and fishmeal have been on an upward trend and contributing positively to the balance of payments in many developing countries in Asia and Latin America. Particularly marked expansions in export trade have been achieved by Thailand and China. The developed countries, especially those of the European Community, Japan and the USA, remain the principal importers, accounting for some 88 percent of total world fish imports. The USA has also become the world's major exporter of fish and fishery products, reflecting gains through the extension of jurisdiction and its increased catch in the North Pacific.
Many major fishing countries, both developed and developing, are both large importers and exporters. Most developing countries in Asia, for instance, carry out simultaneously import and export trade in fish, exporting high-value species not consumed domestically and importing fish and fish products of lower prices and quality. Export-oriented fisheries may involve the use of imported inputs (e.g. frozen tuna in Thailand). With the growth of domestic economies and per caput incomes, some exporting countries may find it difficult to maintain exportable supplies in the face of expanding domestic consumption.
The rise in prices for some fish products is being constrained by market-place competition from alternative foods. On the other hand, the culture of certain species, notably salmon and shrimp, is now producing sufficiently large quantities to put pressure on market prices. The development of new products, particularly those involving the processing of low-valued species (e.g. Alaska pollack) into reconstructed high value products, may also have some impact on prices.
Demand and taste preference for fish and fishery products and supply patterns are continually undergoing changes. As prices for the more highly preferred species rise, middle-class consumers tend to turn to species traditionally consumed by the poorer sections of the community. At the same time, although the catch of less favoured, unconventional species is increasing due to the increasing production constraints of commercially preferred species, their availability, particularly for low-income consumers in Asia, is being reduced as a result of competition from aquaculture feed demands and the degradation of coastal areas.
6.3 Prospects for the future: production
As noted, there are severe constraints to increasing aggregate fish production. The little further growth that can be achieved in sustainable ways is unlikely to be sufficient to maintain per caput supplies. Unlike other sectors of agriculture, it is more difficult to relax the production constraints in fisheries by bringing new resources into exploitation, technological change and investment. Often efforts to improve management of fishery resources will be primarily aimed at preventing current production levels from declining.
Table 6.3 Present and possible future production levels of fish (million tonnes, liveweight)
Note: Details on production by major fishing areas are given in the Annex.
Much of the increase in catch during the 1980s came from pelagic species which are subject to wide natural fluctuations and appear to have recently passed their peaks. Some stocks are now facing significant declines. If the catches of these kinds of fish cannot increase further, the growth of the fishmeal-dependent aquaculture sector will be accordingly constrained unless technological advances are made in providing alternative sources of feed. Moreover, the major demersal species throughout the world have been overfished and they provide little opportunity for increased catch except through improved management, which inevitably will require some reduction of fishing over the medium term to allow stock rebuilding.
Marine catches can only be increased marginally over current levels. This would still entail a real risk of changing the nature of the marine food chain and affecting other species dependent on it. Total marine catches are not likely to greatly exceed 100 million tonnes and could be considerably lower. Aquaculture production may range from some 15 to 20 million tonnes from the present level of 12 million tonnes assuming that the growth rate prevailing in the last few years will be maintained. Increases in inland capture fisheries may be insignificant unless improved management of resources is combined with a better environment.
The above considerations make it clear that estimating future production levels is an operation subject to many uncertainties. With this caveat in mind, indicative estimates are given in Table 6.3. These hypothetical estimates could be feasible with better management and other interventions (e.g. sea ranching) which would favour recovery of fish stocks. The rest of this section discusses the factors that are likely to shape the future in the different country groups and species. A schematic presentation of the status and likely future potential by major fishing areas is provided in the Annex at the end of this chapter.
The developed countries
The developed countries (aside from Australia, New Zealand and South Africa) derive most of their supplies from capture fisheries in the northern temperate zones in both the Atlantic and the Pacific Oceans and from inland waters; tuna stocks in all oceans; and culture of certain species (e.g. salmon, catfish, shellfish). They also, of course, derive some supplies from imports. In developed countries technological innovation and high demand for fish have led to heavy exploitation of stocks in adjacent waters.
The northern Atlantic, the northern Pacific and Mediterranean/Black Sea where developed countries are mainly engaged in fishing, are generally considered to be overfished. At present there are very few instances of successful management, either in the multinational fisheries of the European Community or within the large exclusive zone of the USA, and there is a serious need for catch restraints to allow stock rebuilding. Although, in theory, further increases in supplies could come from the development of underutilized stocks, these are few in number and low in value and are often food fish for higher value species. The largest opportunity appears to be in the further development of the cephalopod fishery in the north Atlantic and the northern Pacific, if this can be done without affecting ecologically important by-catch species.
The situation is more serious for a few developed countries who have continued to acquire supplies from coastal countries because of high royalties and increasing costs of operation (e.g. Japan, Spain). The former USSR, an important distant water fishing nation, may play a reduced role as the heavy subsidies are being removed from the industry. Catches from the inland waters of the developed countries are relatively insignificant, except in the case of the former USSR. For many developed countries, aquaculture is becoming of increasing importance in meeting the demand for certain high value products. The most significant, at present, is from the culture of salmon. Other species include catfish in the USA, carp in the former USSR and seabream and amberjack in Japan.
The developing countries
The situation is relatively more favourable in some developing countries where resources are less overexploited than in the developed countries. For Africa and the Near East, the major sources of supply are the capture fisheries in the east-central and southeast Atlantic, the west Indian Ocean, and the inland lakes and rivers. Aquaculture is not, at present, an important source of fish. The west African coastal countries have significant opportunities to increase their share of the existing harvest of their coasts. However, much of the catch is of low-valued species and is now harvested by large-scale foreign industrial vessels. As industrial fisheries are a capital intensive and high-risk sector, some of the coastal countries may still have to depend on extracting rents from foreigners while others expand the development of inshore fleets through joint ventures. There are very large unexploited resources of lantern fish (a mesopelagic species) which are found in relatively deep waters and are suitable for fishmeal. However, it is questionable whether their harvest will become economically feasible before 2010. Inland fishery resources are of importance as sources of food in many countries. However, significant increases are not likely to occur.
For Latin America and the Caribbean, most of the species fished in the Gulf of Mexico and Caribbean are heavily overexploited and the major opportunity for an increase in catch is from squid and octopus. The stocks of cephalopods on the Patagonian shelf appear to be fully exploited though there may be opportunities for increased catch of other cephalopod stocks in the northern coastal areas. The coastal countries may have the opportunity to increase their share of the catch presently taken by the distant water vessels. The northern areas of the west coast of Latin America contain large stocks of small pelagics which are subject to the influence of the current "EI Nino" and fluctuate widely in abundance. The catch of Chilean jack mackerel has grown from negligible amounts in the mid-1970s to 3.8 million tonnes in 1990. The stock is considered to be only moderately exploited and may allow for some continued increase in catch. Aquaculture is not of great significance in Latin America with the notable exception of Ecuador and Chile which produce shrimp and salmon respectively, mainly for export. The prospect for the latter is dependent upon international market demand which appears to be presently saturated.
For Asia, the demersal stocks of the East and South China Seas, the Yellow Sea and the Gulf of Thailand are heavily fished. It is unlikely that recovery of these stocks, if effective management measures were to be implemented, would add more than I million tonnes to total catch. The pelagic stocks are fully utilized and no significant increases would be possible. There may be some possibilities for an increase in catch of cephalopods along the Chinese coast. The great majority of China's aquaculture is of herbivorous carp so that production would not be constrained by shortages of fishmeal. Increases may be feasible in eastern Indonesia where distance from markets has restrained development. Fisheries for large pelagic species and small tunas have doubled their catch in the last two decades and although there may be moderate potential for increase in the future, restrictions on dolphin by-catch may affect use of purse-seines in the future. There may be opportunities to increase the total catch of skipjack. The cephalopods are moderately exploited and may have increased in abundance as a result of the heavy exploitation of the predator demersal fish.
Brackish water and marine culture of shrimp for export to the developed countries has increased dramatically, but shrimp culture is beginning to encounter and cause some difficult problems due to disease and organic pollution from shrimp farming and limited space for expansion. Overall, improved management could lead to the largest increase in supplies to the region. Additional supplies might come from increased harvest of cephalopods and further development of resources of eastern Indonesia and the eastern Indian Ocean.
Coastal countries of the Indian subcontinent may be able to increase their catch of tunas, both the large market species and the smaller tunas. Estimates of potential yields are not available, but it is likely that the catch of skipjack in the western Indian Ocean as a whole could be substantially increased. Increase in the other large tunas may be possible but is not likely to be significant.
Inland fisheries, particularly in India and Bangladesh, provide important sources of protein for local markets. Significant improvements could be made in both countries in culture practices and in the use of water bodies where problems of ownership impede effective production.
Production prospects by species
In most of the major fishing areas production has reached a plateau and in some areas fish yields are on the decline. In some cases production levels are being maintained by catches of younger fish, and certain localized areas are particularly vulnerable. Below, supply prospects are reviewed by species.
Crustaceans are generally heavily exploited and wild penaeid shrimp production is close to a ceiling. Landings are unlikely to decline as the industry is currently overcapitalized. Penaeid pond shrimp production may also be approaching a saturation. Problems surrounding shrimp culture are the availability of fry, space, feed and environmental degradation, and, in particular, the heavy dependence on wild fish catches for feed. The main determinant of increased output will be the cost of inputs in relation to the price of shrimp. A significant potential for expanded catch can be expected from minor crustaceans (e.g. crabs and small shrimps). Molluscan shellfish, which do not depend on fishmeal, may offer good opportunities in both developed and developing countries depending on markets but face deteriorated environmental conditions. In the tropics there are potential resources of bivalve stocks.
For cephalopods the possibility of increased production, particularly of oceanic squids, is generally good and future levels of output are likely to depend as much on market considerations as on resource availability, as well as on technological developments in capture and processing. The banning of large driftnets in the northern Pacific could even result in a decline in catches unless new, efficient and environmentally-friendly gears are devised.
The present level of exploitation of demersal fish has reached the maximum and there is no potential for increased production. Stocks of cod and other groundfish have declined. Although some potential for increasing supplies exists from use of discards of lower-value species and small flatfish, in both the north Pacific and Atlantic the fishing effort has already shifted to lower-value species (e.g. blue whiting). The tightening of controls in certain countries (e.g. Morocco, Chile, Namibia) could reduce fishing operations and the total allowable catch (TAC) in order to allow rebuilding of groundfish stocks. This is likely to have a negative role on landings in the short to medium term. With good management, long-term potential would be no more than 20 to 30 percent above the present levels.
The immediate situation for small pelagics seems to be pessimistic. The largest global single species (i.e. the Japanese pilchard) has declined again in recent years and its recovery is likely to depend on climatic factors. The principal small pelagic fisheries of the southeast Pacific are also declining. The retrenchment of the long-range fisheries of the former socialist countries is unlikely to be offset by increased interest by other countries in establishing joint ventures with coastal states to exploit small pelagic species for food. It is unlikely that significant increases in krill production will be realized for a combination of economic and biological reasons. The current annual krill harvest of 300000 tonnes compares with a possible yield of 3.9-6.5 million tonnes as determined by the Commission for Conservation of Antarctic Marine Living Resources. The limited production has been caused mainly by economic and marketing factors and substantial increases in catches are not anticipated for the short to medium term. The future for these fisheries may be tied to improved technology which can convert them to higher valued products and suitable promotion.
Given the spectacular success of salmon farming, and the possibility of its extension, the potential for increased production in the medium and long term is good. By overcoming the problems relating to a market glut through the reduction of input costs, increased production can be expected from improvements in wild stocks and ranching in the medium term. The Russian Federation has promising prospects for increasing salmon production through improved ranching.
Although some significant potential exists for the smaller tunas, tuna-likefish and skipjack in the medium and long term, its materialization will greatly depend on fuel costs and markets. Conventional tuna fisheries will also be affected by the marine mammal factor which may restrict further expansion of the use of purse seines and large-scale gillnets.
Although some growth can be expected from inland fisheries, the most interesting developments in this sector in the medium and long term are likely to depend on stocking programmes to enhance the stock in floodplains, rivers, reservoirs and irrigation ponds and in intensive management of small water bodies. Inland aquaculture may also have some potential for development in Latin America and Africa.
Overall assessment of production prospects
Past estimates of the annual potential supply of fish from all sources have ranged from 100 to 120 million tonnes. It is now evident that the marine capture fisheries are adversely affected at extraction levels beyond about 80 million tonnes. Inland capture fisheries' yield is about 6.0 million tonnes, of which Asia produces half and the overwhelming constraints to further increases in production rest with the appropriate allocation of water rights and water quality.
Aquaculture, although recording a remarkable growth over the period 1984 to 1990, has experienced significant problems in saturation of markets and consequent price reductions as well as environmental and disease setbacks. These, however, are expected to be only temporary and characteristic of a growing industry. The major constraint would appear to be the restricted knowledge of the requirements for growing only a relatively few species. Most notable is that finfish farming has mostly occurred for freshwater herbivore species (7.4 million tonnes) with only a modest contribution from marine species (1.0 million tonnes). The further expansion of finfish supplies from freshwater aquaculture is likely to be constrained by the freshwater environment. By contrast, the marine environment offers far better prospects for production growth, provided technology can overcome difficulties in locating pens and cages further offshore. With the exception of molluscs, carps and tilapia, the growing of fish in captivity is still in its infancy and can be compared with early attempts at animal husbandry and the domestication of wild animals.
The greatest prospects for increasing fish supplies for food are to be found in the use of small shoaling pelagics for direct human consumption. Presently these species are used for producing fishmeal, for pig and poultry production as well as for aquaculture. The salmon and shrimp aquaculture increasingly use higher-quality fishmeal as feed. This requires an upgrading in the method of harvest and handling of the low-value fish used in the production of fishmeal with consequent increases in the unit cost ax-vessel. Such increases in the price of low-value species can have adverse effects on the poorer segments of population who consume them as food, mainly in Asia. In contrast, in Latin America the supplies of this type of fish for human consumption may actually increase as the upgrading of their quality for the production of aquaculture feed would also make them more acceptable for human consumption.
The remaining option for increases in fish supplies would be that the present condition of overfishing prevails and that the majority of the marine catch increases would come from fishing further and further down the "food chain". The end limit, as has occurred in one or two areas, is a fishery that is almost entirely a "trash" fishery of mixed juveniles and other small-sized species for direct feed to grow several preferred species. That is to say, the wild production from the marine areas could end up being nearly all utilized to grow two or three species in captivity. The impact would be the loss of the present wide spectrum of food items that the existing 1000 commercial species now provide, to be replaced by very few species providing only differences in flesh, colour and texture.
Estimates of potential from mariculture are precarious to make at this juncture with only a short time-series of production showing a spectacular increase. However, there are projections of 500000 tonnes of farmed salmon production by the year 2000 and these may be projected to 2010 by a further doubling. Shrimp farming produced 700000 tonnes in 1991 and has been projected to expand at a reduced rate, estimated at I million tonnes by 2000 as a result of constraints in expertise, pollution, disease, infrastructure and market fluctuations. Any projections for farmed fish will be determined by demand pull and the price relationship between capture fish and other food products.
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