Economic Pressures Driving Genetic Changes in Fish
NICK C. PARKERAbstract: The demands for fish and fishery products in this country and throughout the world are expected to continue to expand faster than the supply of fish. The new tools of genetic engineeringgene insertion, cloning, androgenesis, gynogenesis, transgenetic production, ploidy manipulationand other techniques will be used in conjunction with selective breeding and hybridization to produce fish tailored for selected environments or with exceptional traits. Data from the Food and Agricultural Organization in Rome indicates that the global supply of fishthe catch from the ocean, inland waters, and all farm-reared aquatic productsincreased 11% from 1982 through 1988. During this time, the volume of fish traded among 162 nations increased 16% indicating a more rapid increase in demand than in supply. Introduction Imports of fish and fishery products into the United States were valued at $365 million in 1960 and $8.8 billion in 1987, when the imports consisted of $3.1 billion worth of non-edible products (animal feeds, industrial products, etc.) and $5.7 billion for edible fishery products. Recently, imports have expanded at an average rate of $860 million per year from 1982 to 1987, while exports increased at only $120 million per year. The annual per capita consumption of fish increased over 20% from 1975 to 1987, when the per capita rate reached 7.0 kg; it is expected to be 13.6 kg by the year 2020. Based on data from the Food and Agricultural Organization, the world's catch of fish (millions of metric tons) was 27 in 1954, 57 in 1966, 74 in 1976, 83 in 1984, and 90 in 1986. The catch has increased with the demand only because previously unused resources ¾ those formerly classified as "trash" fish ¾ are now being captured and processed into consumer-acceptable forms such as imitation lobster, shrimp and scallops. The ocean's resources are recognized as finite, having an estimated maximum sustainable yield of about 100 to 120 million metric tons. The expansion of demand in a market with limited supply is expected to continue to drive prices up and to make fish farming even more lucrative than it is today, when more than 11% of global fish landings are produced by aquaculture. The forecast is for the global yield from aquaculture to increase to 22 million metric tons by the year 2000 when farm-raised species will represent 25% of the world's harvest of aquatic organisms. Demand for Game Fish Increases According to survey conducted by the U.S. Fish and Wildlife Service in 1985, 58 million anglers spent $28.2 billion in 987 million angler days. (U. S. Fish and Wildlife Service 1988). Sport fishing is projected to double by the year 2030. The fishing pressure on public waters is expected to increase much more rapidly than the ability of the resource to produce. Even today some anglers have abandoned public waters to fish in more productive private waters. Public waters often yield less than one legal-size bass in10 hours of fishing, whereas 30 to 40 bass can be taken from some privately owned and managed lakes in only 3 or 4 hours. Many U.S. citizens are willing to buy catchable-size fish to be stocked in private ponds for recreational purposes. Others are willing to pay sizable fees to enjoy quality fishing in private waters.
Aquaculturists are producing hybrids of striped bass and white bass, Florida strain largemouth bass and other warmwater species for food and sport fish. Some anglers have paid $900 per day for the opportunity to catch 3-kg trophy-size bass in private waters and other fishermen routinely pay $90 in the off-season and $165 per day in the peak season to fish for 1- to 2-kg fish (Parker 1988). Adoption of the user-pay philosophy has long been evident in private hunting clubs and on game management areas requiring special licenses and fees. The growing popularity of feefishing operations offers expanded opportunities for selling farm-raised fish for recreational purposes.
The catch from privately owned fee-fishing operations is frequently so high that it resembles a supermarket activity. In a single day anglers have harvested over 500 kg of channel catfish from a 0.1-ha pond. Activities such as these may relieve the fishing pressure and certainly provided recreational opportunities in excess of those available on public waters. In many locations public waters are already being managed as catch and release fisheries. If fishing pressure increases as projected, a greater percentage of the commercially captured fish will be redirected to recreational fisheries. Farm-raised fish ar expected to become increasingly important for food and recreational purposes.Expected Contributions of Genetics Domestic beef, poultry and swine have evolved through selective breeding over thousands of years and are quite different today from their ancestral stocks. By contrast, man has had little influence on genetic selection in most fish. Man's activities to domesticate and improve livestock were directed to a limited number of species whereas the gene pool of fishes resides in thousands of freshwater and marine species of which only a few ¾ predominately goldfish Carassius auratus, common carp Cyprinus carpio and rainbow trout Oncorhynchus mykiss ¾ have been selectively bred in excess of 100 years.
In recent years, a few other species have been selectively bred as tropical or hobby fish or for the recreational and food-fish markets; the likelihood is that well under 1% of the estimated 20 to 25 thousand species of finfish have been spawned in captivity. The percentage of molluscan and crustacean species that have been spawned in captivity is probably similar to that of finfish.
Geneticists are increasingly turning their attention to fish and in conjunction with aquaculturists have produced common carp and channel catfish Ictalurus punctatus which carry the human gene for growth hormone (Dunham et al. 1987). Others are justifiably concerned about the influence of hatchery stocks on the population structure of indigenous stocks (Ryman and Utter 1987). It seems likely that aquaculturists, managers of natural stocks, and those interested in fish for recreation and the commercial fisheries will turn to geneticists to "improved" their stocks. Fish will be selected and developed to thrive in modified environments, to tolerate extremes in temperature, dissolved oxygen, pH, and other water quality variables. Sport fish records will fall in every category as gentically improved fish are stocked in public and private waters. Androgenesis and gynogenesis coupled with reversal of genetic males and females into functional individuals of the opposite sex and then mated back with their own genotype, will produce monosex populations posing little threat to native species. Hybrid and polyploid individuals will become increasingly more popular and widespread due to unique characteristics which may include rapid growth, disease resistance, trophy size, and their ability to fill niches unoccupied by other fishes. The genetic tools being developed and perfected for human medicine and animal sciences will be increasingly applied to fish due to growing economic incentives.Proposed Action Aggressive positive programs must be established quickly if the demands for food fish and sport fish are to be met. According to U.S. Department of Commerce figures, the 1987 trade deficit for fish and fishery products ($7.1 billion) was 4.1% of the total U.S. trade deficit ($171.2 billion) and, excluding manufactured goods, was second only to the deficit for petroleum and petroleum products ($16.2 billion) ¾ 9.5% of the total. By comparison, the top five agricultural products imported, listed by actual value and as a percent of the total deficit, were vegetables and fruits $4.3 billion, 2.5%; coffee $2.8 billion, 1.6%; crude rubber $1.2 billion, 0.7%; cocoa $1.1 billion, 0.6%; and sugar $0.4 billion, 0.2%.
The export value of several other agricultural commodities exceeded their import value, resulting in a positive trade balance for these few items. These agricultural trade surpluses in billions were as follows: soybeans $4.3, corn $3.3, wheat $3.0, cotton $1.6, rice $0.5, and tobacco $0.5. Each of these commodities produced in surplus have benefitted from strong government support programs, including research, extension, loans and even price support. Similar positive action programs for aquaculture, if funded at just a small percentage of the trade deficit for fish and fishery products, would produce almost immediate benefits. These benefits would reduce the deficit, establish new jobs for U.S. citizens, provide additional food fish for consumers and sport fish for anglers, and better prepare American fish farmers to compete in international markets. Even with this positive action, the trade deficit in fish and fishery products is expected to continue its upward spiral as the demand grows and the supply shrinks. The economic incentive to produce specialty fish or "improved" fish will draw more geneticists into the fisheries field. Natural resource managers may face their greatest challenge in trying to balance the public's demand for genetically improved fish with the preservation of native stocks.Literature Cited Dunham, R.A., J. Eash, J. Askins and T.M. Townes. 1987. Transfer of the metallothionein-human growth hormone fusion gene into channel catfish. Trans. Am. Fish. Soc. 116:87-91.
Parker, N.C. 1988. Aquaculture - natural resource managers' ally? Trans. 53rd N. Am. Wild. and Nat. Conf. 53:584-593.
Ryman, N. and F. Utter, editors, 1987. Population genetics and fishery management. University of Washington Press, Seattle.U.S. Fish and Wildlife Service. 1988. 1985 National survey of fishing, hunting and wildlife
asssociated recreation. U.S. Department of Interior, Fish and Wildlife Service, Washington, D.C.
Reprinted from: Pages 415-419 in A. Rosenfield and R. Mann, eds. Dispersal of Living Organisms into Aquatic Ecosystems. 1992. Maryland Sea Grant Publication, College Park, Maryland.