The need for conservation of fish genetic resources has been recognized by fishery scientists and aquaculturists for some time, especially in relation to overfishing of natural stock, the effects of large-scale alterations to river systems, and domestication of species through aquaculture. The FAO World Symposium on Warm Water Pond Fish Culture (Rome, 1966) stressed the importance of genetic selection and hybridization in improving fish varieties for culture and noted problems of excessive inbreeding on carp farms. Need for an international system of designating strains and stocks was also recognized. In 1971, FAO established an ad hoc Working Party on Genetic Resources of Fish, which reviewed progress in genetic selection for fish farming, identified priority areas for research and made several recommendations for the conservation of fish genetic resources. Included were suggestions that methods for doing so needed urgent study, that a catalogue of threatened genetic resources of potential use to aquaculture should be prepared, and that the collection of wild species of potential usefulness should be undertaken. These actions have not taken place, largely because there has been no consensus on the criteria that are needed to limit such work to manageable proportions. The FAO Technical Conference on Aquaculture, held in Kyoto, Japan, 26 May to 2 June 1976, reaffirmed the need to maintain the genetic diversity in artificially propagated stocks, noted that indiscriminate transfer of fish and shellfish have, in some cases, had adverse effects on indigenous stocks, and called for increased research on fish genetics as there was a substantial lack of information on this subject, making the formulation of selective breeding programmes difficult.
One strategy for conserving the diversity of natural populations of fish and other organisms is to set aside aquatic reserves. The International Union for Conservation of Nature and Natural Resources (IUCN) has been active in promoting marine parks, and with the cooperation of the Government of Japan, the World Wildlife Fund and UNEP, held an International Conference on Marine Parks and Reserves in Tokyo, 12 to 14 May 1975. This conference reviewed the conclusions and recommendations of earlier regional and world conferences concerned with the marine environment and proposed, inter alia, that IUCN and other concerned agencies “develop a coordination strategy to satisfy forthcoming requests for assistance [to developing countries in the establishment of marine parks]”, and “set up teams to undertake appropriate surveys to enable systems of marine parks and reserves to be based on the best available data, to assist in the formulation of appropriate conservation policies relating to marine parks and reserves, and to identify those projects suitable for bilateral and/or other technical cooperation programmes”.
The United Nations Conference on the Human Environment, Stockholm, 1972, produced recommendations emphasizing, inter alia, the need for conservation of all genetic resources. In its third session (1975) the Governing Council of the United Nations Environment Programme requested, among other things, the preparation of an overview on the problems of the conservation of genetic resources as part of an overall report on the conservation of genetic resources. The Food and Agriculture Organization, through a cooperative project with UNEP (FP/1108-75-01) prepared a paper which included a brief review of the problems and requirements for action on fish resources (UNEP/PROG./4). This overview has now been revised and produced by UNEP as UNEP Report No. 5 (1980), “An Overview of Genetic Resources”. The report emphasized that the basic constraint is lack of knowledge and recommended, among other things, the need for a mechanism for monitoring changes in the genetic diversity of fish populations, for promotion of research directed at creation of knowledge on the genetics of fish which would assist in a more applicable definition of genetic impoverishment in fish species and for promotion of research on appropriate methodologies for conservation.
During discussions held in FAO, Rome, in June 1979, it was agreed that the variety of needs and problems associated with this aspect of genetic conservation could not be adequately reviewed and assessed by a single individual. It was proposed that a group of experts be convened to accomplish this review and propose a balanced and practical programme of action.
It was then agreed that FAO would organize an expert consultation, in cooperation with UNEP, and with the participation of Unesco and IUCN, to be held in Rome, 9–13 June 1980.
The purpose of the consultation, as stated in a prospectus sent to prospective participants, was:
Subsequently, it became evident that the consultation needed to focus primarily on the scientific aspects of the problem, considering especially the nature of the threats to genetic diversity of fishes, both among and within species, methodologies for monitoring and assessing change in genetic diversity, and identifying feasible actions which might be taken to conserve diversity. The development of a comprehensive and coherent action plan for implementation by governments was seen as a subsequent step. Thus, in the course of the consultation, the experts were urged to address recommendations to several different kinds of people or institutions: scientists, conservationists, fishery managers and aquaculturists, governments and international organizations.
The objective of nature conservation is to preserve for posterity as much as possible of the earth's biological and ecological diversity. The justifications of such an attitude span a very broad range of human thought and experience - from divinely inspired ethics to short-term economic and political gain. At the one extreme some people argue that morality dictates the right of all species to persist and evolve, and that man's power to alter and destroy the biosphere does not give him the ethical licence to do so. On the other hand, there are those who argue from the standpoint of human welfare - that the preservation of biological diversity is only common sense, and that the prudent strategy is to keep the options open by preserving genetic diversity in order to sustain production in agriculture, forestry, fisheries and other natural products and to minimize the threats of ecological disasters such as climatic alteration, erosion, siltation, desertification and pollution.
While there is no “best” approach or justification, there are appropriate ones. Genetic resource preservation is one such tactic. The approach taken by proponents of Genetic Resource Preservation is pragmatic. As a matter of human welfare, it is essential that production of natural resources increases. Fish are an important source of protein and other valuable organic products. Therefore, the protection and exploitation of options for the improvement of fisheries and aquaculture is a high social priority. The accomplishment of these goals depends to a large and increasing extent on technology and science and it is the role of genetics in this effort to which this report is directed. An interest in and knowledge of the role of genetics in the enhancement of fisheries production does not necessarily make one a conservationist. But such knowledge will make a more effective soldier in the battle to feed the rapidly growing human population.
It is convenient and heuristic to distinguish two processes by which genetic resources are lost; these are (1) the extinction of a species and (2) the reduction of genetic variation within a species. The former process, once it occurs, is qualitative, final and irreversible. The latter process is a matter of degree, and is to some extent reversible.
This report discusses aspects of both processes because both are clearly relevant to the maintenance of options in fisheries. Nevertheless, the relevance to exploitation of these two processes depends on the stage of development, its intensity and the degree of human control in the fish extraction enterprise. These problems will be dealt with throughout the report.
A realistic perspective on the process of extinction and its current status is essential for those in the resource fields. Of special import is the current change in rate of extinction. Barring periods of dramatic climatic swings such as the Pleistocene, both the origin and extinction of species have probably gone on at similar rates for hundreds of millions of years. Now, however, due to habitat destruction by man, extinction rates are probably three or more orders of magnitude higher than ever before (Myers, 1979; IUCN-UNEP-WWF, 1980), while the rate at which new species of large organisms appear, especially in the tropics, is approaching zero (Soule, 1980). Hence for groups of organisms that occupy disappearing habitats, it is not likely that organic diversity will ever again reach its present levels.
For fishes the situation may not appear to be so severe, but one must specify the place and the group. Habitat destruction in the oceans is not yet appreciable. At least no significant or detectable increase in extinction rates has been observed in the oceans (although populations have been extinguished from overfishing and pollution). For other aquatic habitats, however, the situation is already deteriorating rapidly. The issue boils down to one of disparate time scales. The time scale for pollution, exploitation or development is measured in years, decades or centuries, whereas that for speciation is usually measured in much longer intervals.
For example it may only require ten years to dam a river, thus creating a habitat inimical to the existing riverine fauna dependent on periodic flooding or moving water. On the other hand, the lifetime of the resulting reservoir will be too short by thousands of years for the evolution of lacustrine forms of fish.
Similar arguments could be made for the effects of pollution and siltation on rivers, lakes, estuaries, lagoons and reef habitats. Obviously, it is naive to entertain the sanguine expectation that evolution of new species will compensate for the loss of biological variety during the next few decades.
The assumption that underlies the discussion in this section is that the manner in which a resource is exploited is as important in the long run as the degree to which it is exploited. More explicitly, the way in which fish populations are managed will largely determine the success of the enterprise. This comes as no surprise to fisheries biologists, but there is a dimension to management that has been relatively ignored - the genetic dimension. One of the objectives of this report is to underscore this dimension and by so doing, to anticipate and thereby prevent the very serious loss of options that has already occurred in agriculture (National Academy of Sciences [US], 1972; Heslop-Harrison, 1974), and to a lesser extent in animal husbandry (Frankel and Soule, 1981; FAO, 1975).
Fish flesh is an important source of high grade animal protein. With a growing world population and rising expectations for living standards, the pressures on fish both as a source of food and for its byproducts can only increase in the future. At present fish and aquatic animals constitute 17 percent of the total animal protein in the human diet. This statistic conceals wide regional differences in fish consumption. For example, 32 countries obtain 34 percent or more of their animal protein from seafood. On the African continent, ten countries obtain over 40 percent of their protein from fish. In 21 countries on the same continent over half of the fish landed comes from inland lakes and rivers, and in 13, the fish supply is entirely from inland sources.
The potential for further growth of natural marine and freshwater fisheries is limited. Already the total world harvest is 15–20 million tons lower than it might have been had fishing been strictly controlled through scientific management, and 25 valuable fisheries have been seriously depleted by overfishing. Other factors which limit the contribution of marine fish to the diet include problems of distribution, storage and cultural inhibitions to its consumption.
Intensive fish farming can, in principle, overcome two of these limitations. Fish farming activities may often be sited near to the markets in which the product is sold. They also avoid the depletion of biological resources except where still dependent on the collection of seed from the wild. Fish farming not only allows the products to be delivered directly to their markets but it also represents both a renewable and inexhaustable resource. Aquaculture is still in a relatively early stage of development and the production of new strains and races of food fishes will require careful management of available genetic resources. The lesson learnt from extensive breeding in crop plants and in domestic animals is that a narrowing in the genetic base of the species is inevitable. In such processes, genetic determinants which are likely to be lost at an early stage include those controlling disease-resistance and fitness in marginal environments. It is hence prudent for breeders to be especially mindful of the need to protect and preserve, at the earliest stage possible, broad genetic diversity within those species most likely to come under intensive breeding pressure.
Fisheries not only provide a significant portion of the protein available for human consumption -they are also an economically significant activity, providing jobs and investment opportunities, and, for many countries, a means of improving the balance of international trade.
Certain species of fish are, by virtue of special or unusual biological features, useful as experimental animals and as a source of biochemical and pharmacological agents. Often species and genetic traits to be preserved are not the same as those for food fishes. Since only a handful of the 25 000 plus species of fish have been subject to scientific scrutiny the extinction of any species may represent a potential loss of an economic resource.
Substances isolated from fish and other aquatic animals are already widely used in medical research. For example, tetradotoxin (TTX), a toxin isolated from the puffer fish, Tetraodon immaculata, is used in neurophysiological research as a specific sodium channel blocker and is playing an important part in reaching an understanding of the basic ionic mechanisms of nervous transmission.
Another class of compound used as a research tool is luminescent proteins. For example, Aqueorin from a jellyfish species has been widely used to monitor the Ca2+ concentration in cells. Ca2+ serves as an important signal in transmitter/hormone release, and in excitation contraction and excitation-secretion coupling. An understanding of such processes is important in the development of new drugs and in the treatment of disease. It is likely that fish toxins, hormones, glycoproteins and naturally occurring polypeptides constitute a large and relatively unexplored reservoir of compounds of equal pharmacological interest.
Other natural products, notably oils and waxes, have long established industrial uses, e.g., for vitamin enhancement of animal feedstuffs. New applications for these byproducts might include substitute natural bases for medications and cosmetics. In many countries fish meal is already widely used for feeding domestic animals and as a major source of fertilizer.
In cases where species are threatened with extinction, establishing the importance of natural products remains an issue of high priority. The economic and social benefits provided by such discoveries, however, go far beyond the immediate value of the fish as an economic resource. The history of natural resource utilization tells us that the ultimate value of any genetic resource may not be appreciated at the present time.
Nor is it sufficient to stave off extinction by preserving a small handful of individuals. It is not uncommon that the genetic determinants are not evenly distributed within the species - in quantitative or even qualitative terms. This presents a strong argument for preserving broad genetic diversity within a species, if its socio-economic potential is to be realized.
Another important area of economic activity relates to sport fishing. Increasingly, freshwater sport fisheries are ‘scientifically’ managed and restocked from hatchery populations. Freshwater fishing in countries such as Ireland and marine sport fisheries in various tropical countries are a major factor in the development of tourism. Thus sport fisheries can increase employment and support and stimulate a wide range of ancillary economic activity. The creation of classes of marine reserves where controlled fishing is permitted may provide a valuable way of safe-guarding the species diversity of coastal areas while providing a good economic return from anglers and day visitors.
In North America, Europe and South-East Asia, the ornamental aquarium trade is a major industry. For example, the wholesale turnover of tropical fish in Florida (U.S.A.) alone in 1974 was in excess of $30 million (Courtenay et al., 1974). Many of the most popular species come from the Amazon basin and the Great Lakes of Africa. These fish often occur in small discrete sub-populations which live in highly specialized or localized habitats and are thus extremely vulnerable to extinction. Properly guided and encouraged, the culture of such species by hobbyists could be one way of preserving this resource for future generations. However, owing to the danger of inbreeding, in situ conservation is much more likely to be successful. Salt water coral reef fishes provide similar potential for income as well as similar problems for the long-term protection of the resource.
Certain species of fish are now being seeded into lakes and rivers for use in the control of weeds and insect pests. This may have significance in the elimination of vector-borne disease. While this is socially and economically desirable attention should be paid to the effects on indigenous fish populations (see Section 5.3).
In summary, in order to keep our economic options open, it is desirable to implement aggressive programmes that operate on both levels of genetic resource preservation - programmes that (1) minimize the rate of species extinction by mitigating habitat disruption and that (2) minimize the erosion of genetic variability of species in no immediate danger of extinction, especially of those which already play major economic roles in human survival.
The principle ecological argument for the preservation of fish genetic resources is, in a sense, the logical converse of the preceding arguments. It is as follows: Stability of ecological systems and the maintenance of biological (taxonomic) diversity is a universally acknowledged value, although social and economic considerations may often be granted a higher priority. One important means of maintaining stability and diversity is the maintenance of fitness in species, particularly the dominant, high trophic level consumers. The depletion or extinction of such species constitutes the loss of genetic resources and is a threat to the integrity of ecosystems.
Habitat protection is the best way to insure the survival of ecologically important fish species. Habitat destruction is particularly disastrous when local endemic species are involved because the elimination of an entire species is an irreversible process (see Section 1.4). We expect this to be an increasing problem, particularly in tropical areas where endemics with narrow habitat requirements abound. While some decay in water quality and habitat diversity can be tolerated, there is probably a point at which even partial destruction of habitat integrity can reach genetic and ecological thresholds that result in the precipitation of extinctions. Some tropical ecologists believe that the extinctions of certain key species will bring about a rather sudden cascade of linked extinctions (Gilbert, 1980; Terborgh and Winter, 1980). In summary, a concern for survival of species, and the development of appropriate preservation programmes and guidelines, will indirectly benefit man by protecting entire ecosystems and all their attendant economic and ecological values (World Conservation Strategy, 1980).