ABSTRACT
This chapter discusses a debate developing about the value of intensive artificial culture techniques in managing salmonid production. The debate is basically whether such techniques provide sustainable increases in total production or may actually contribute to reduced production and persistence of natural populations. Concerns have recently been directed at large scale hatchery projects, including ocean ranching, mariculture, supplementation, colonization and stock transfers, and can be grouped into three sources of impact: genetic, ecological and fishery management. Regrettably, the debate has tended to be more rhetorical than empirical owing to a paucity of critical evaluations. Studies have demonstrated, however, that impacts attributable to each source can occur but that the degree of impact will vary with the scale of the project, its integration with management objectives, and the status of the natural populations.
Intensive culture projects intended to augment natural production cannot be developed or evaluated independently of natural populations, or be perceived simply as technological fixes to harvest or habitat issues. During future resource management planning, decision makers must be aware of and consider the risk of these impacts. I suggest, however, that increased awareness of the need to conserve biological diversity (within and between species) and productive fish habitat will probably direct future enhancement towards smaller scale and/or semi-natural projects. Such a change will also necessitate change in evaluation standards with increased emphasis on conservation, ecological stability and broader social benefits.
Quotes for the text
The issue developing is whether such techniques provide sustainable increases in total production or may actually contribute to reduced production and persistence of natural populations. At present, most concern has been directed at intensive culture in hatcheries. In a broader context, the issue exemplifies increasing international concern for maintaining biological diversity while achieving economic development. Unfortunately, the issue tends to generate more debate than impartial discussion. Enhancement programmes have strong public support and management agencies have significant investments in them, particularly in hatcheries.
Hatcheries have been used in salmonid production for over 150 years. Hatcheries were perceived as a technical means to increase production without significant impacts on natural populations. In Pacific salmonids, however, limited knowledge about population dynamics and inadequate harvest controls resulted in the over-exploitation of many natural populations and decreases in catch.
·there is clearly increased concern about the sustainability of world salmon production and market values, the maintenance of biological diversity within and between natural populations, and the impact of mariculture and enhancement activities on natural populations. In the past 2 years, there have been six international conferences on these issues.
(Riddell uses several examples to illustrate concerns about hatchery enhancement programs: One example is taken form the Columbia River and the decline of coho salmon:)
In North America, one of the largest hatchery programmes is coho salmon production in the lower Columbia River. Natural production has been heavily supplemented through hatcheries since early 1960s, but adult returns did not increase proportionally. Further, in 1990, a petition was filed to list naturally spawning coho salmon in the lower Columbia River under the Endangered Species Act of the United States. However, in June 1991 the petition was denied largely because of transfer of hatchery populations between streams and inadvertent selection for run timing in these hatcheries. In denying the petition the National Marine Fisheries Service stated: Lower Columbia coho are presently comprised of a mixture of fish of various origins, and no evidence was found that there remains a distinct wild population segment of coho salmon in the lower Columbia River.â In this extreme example, a major hatchery programme resulted in the loss of biological diversity within and between coho populations, highly variable adult returns, and did not increase catch.
Biological concerns include changes in the cultured populations and their interaction with natural populations. The major biological lessons would be:
1)To use local populations in establishing the enhancement group and avoid transplanting stocks. Transplanting populations has a high risk of negative impacts on local natural populations and should be used only following careful evaluation and public discussion.
2)The genetic change in cultured fish from their source population is inevitable; but its degree and impact will vary with culture history and practices, the founder population size of the cultured population, an d gene flow between the enhanced and wild populations. Genetic variability and fitness are often positively correlated. Also, most phenotypic variation observed between salmonid populations has some genetic basis, particularly important traits identified in culture impacts such as disease and parasite resistance (implying a co-evolutionary history), migration timing, age-at-maturity and body size. Reduced genetic variability and changes in these quantitative traits could result in strong negative impacts on natural population productivity and their longer term fitness.
3)That concerns for genetic impacts on natural populations increase with more intensive culture practices (e.g. domestication of brood stock or widespread distribution of a successful or readily available hatchery stock) or with small brood stocks, the latter because of increased risk due to genetic drift and reduction of the effective population size. Supplementation programmes may be particularly susceptible to the latter concern. Frequently, small numbers of parents are removed from the wild population to minimize the loss of natural spawners. However, the progeny from these few parents subsequently make up a large proportion of the returning adults in the next generation. Simple genetic models of this situation will demonstrate the risk of a rapid increase of inbreeding in such populations.
4)That disease continues to be a limiting factor in culture production and transmission to natural populations.
5)That survival rates of hatchery fish are usually less than those of wild fish when the two have been directly compared. ·there is increasing evidence that reproductive fitness of hatchery fish spawning in the wild is less than the fitness of wild fish.
Ecological concerns include a wide range of interactions from direct competition of enhanced and wild fish to the determinants of total production in an ecosystem. The major lessons seem to be:
1)That enhancement programmes are linked inextricably to the natural ecosystems; this integration is complex and unpredictable in time and space. Enhancement programmes are an intervention into biological communities and each programme should be treated as largely experimental. Production will always be unpredictable since the fish are released into an uncontrolled and variable external environment.
2)That there is a consistent concern that the scale of enhancement programmes frequently exceeds rearing capacities for enhanced and natural fish.
3)That habitat development can be a useful means to avoid these biological and ecological concerns, but the benefits from these programmes are the most unpredictable since freshwater and marine environmental variation both affect total production.
Fishery management concerns include the integration of enhancement programmes with management objectives, control of harvest, and the social and economic pressures frequently created by large scale enhancement programmes. In this case, the lessons seem to be very consistent across a wide variety of enhancement programmes, and include:
1)That enhancement be fully integrated with management objectives. This integration should begin with programme planning and follow through to the evaluation of benefits and impacts. Lack of integration has resulted in over-exploitation of less productive natural populations (both intra- and inter-specific populations), concentration of production into the most productive stocks, and resulted in significant user group conflict.
2)That enhancement should not replace appropriate management controls. Increased abundance of hatchery fish may achieve a catch objective, but without management controls exacerbate conservation objectives for the natural populations which previously provided the historical catch.
3)That enhancement programmes frequently create strong social and political support. Participation creates support for fishery development·and also tends to impede changes in a programme.
Evaluation should be integral to all projects. Few, if any, enhancement activities are proven technologies because each project involves different populations, problems, and ecological situations. Therefore, each should be evaluated and adapted to what was learned. Assessments have frequently considered only the number of juveniles produced but should emphasize the adults produced and the integration of this production within the total management system. Greater emphasis must be given to evaluating interactions between enhance and natural salmonid populations. Without an improved information base on these issues the rhetoric in this debate will continue.
The existing genetic material and associated habitat are the bases for future production and the continuing evolutionary process in salmonids. Priority must be given to conserving these bases and to increasing the population size of present natural populations, thereby reducing risks of loss from human and/or environmental pressures, particularly in light of environmental stresses expected from global climate change.
Enhancement activities are only one part of an integrated ecological system and must be carefully integrated with natural production processes and utilization plans. Priorities in enhancement will vary between areas, but the past primary emphasis on production should be decreased. Enhancement should be a tool in managing salmonid ecosystems and not viewed as an independent production programme.
Projects must be biologically sound and not motivated by external pressures which realistically cannot be met through enhancement alone. Each project must be periodically reviewed and modified if not meeting its objectives or if new objectives are recommended by management.
Support of the general public and politicians will be required to protect salmonids against trade-off with other resource commodities (water, land, forests, etc.). Many enhancement programmes have begun to cultivate this social support through educational and volunteer programmes. These should be continued and media programmes encouraged for broader communications with the public. However, educational and communication programmes should not isolate enhancement from the natural production systems.
The existing ocean ranching facilities will probably continue to be the focus of the sustainable production debate. These facilities have generally been build for an economic motive. It would be consistent with this motive to treat these facilities as an optimization problem, i.e. to maximize the combined return of natural and enhanced fish while minimizing the operational costs. This process would require agencies to experiment with production strategies in major facilities, to conduct parallel assessments in local natural populations, and to make a long-term commitment to this research. The research would admittedly be costly. But given the extent of ocean ranching world-wide, the costs may be small in comparison with the potential resource losses if such techniques do not provide sustainable production and/or do reduce the persistence of natural populations. Such a direct experimental approach is strongly recommended for an objective evaluation of biological and ecological concerns identified.
Conclusion
·enhancement activities will continue to be important in salmonid management. However, a long history of investment in enhancement and extensive production form these programmes already exists. Salmonid resource managers and policymakers must learn from these experiences and not ignore the concerns identified from evaluations.
Ignoring them perpetuates a fallacy that enhancement programmes can function independently from the natural stocks and ecosystems, and polarizes the issues between groups who should share common goals. ·the loss of biological diversity, from whatever cause is irreversible.
Salmonid management in the future will probably involve more integrated resource management at the ecosystem and watershed levels. To be effective in this forum, natural salmonid populations and productive habitats will have to be maintained, integrated salmon production plans developed, and the social values of this resource established. Otherwise, how can salmonid managers expect other resource consumers to respect and protect the salmonid resource?