The need for implementation of specific genetic principles and guidelines in artificial propagation of Pacific salmon (Oncorhynchus spp.) in the Pacific Northwest has become a high priority in recent years. This need has been emphasized by the adoption of public policies, such as the State of Oregon's Wild Fish and Natural Production policies and regional policies adopted by the Northwest Power Planning Council, that specify objectives for the conservation and management of natural and hatchery populations. In addition, fisheries genetics has been the focus of numerous workshops and symposia during the past 2 years.
Fisheries managers are often required to incorporate genetic conservation, management, and monitoring strategies into management and hatchery production plans. Because of a lack of specific genetic information and direction, managers have often experienced difficulty in dealing with genetic issues, meeting planning requirements and policy intent, and understanding the benefits of implementing sound genetic principles and guidelines. In an effort to assist fishery managers and genetics experts and to provide a conduit for information transfer, I conducted a brief survey of fishery managers in the Columbia River Basin to identify priority genetic questions associated with artificial propagation. Based on the responses, I compiled a summary of what I believe are the most critical genetic concerns, uncertainties, and questions associated with artificial propagation of salmon in the Pacific Northwest. Because the goals, objectives, and strategies of different hatchery programs vary considerably, the key questions and genetic risks also depend on the type of hatchery program under consideration. I characterized questions for the three predominant types of hatchery programs that are presently used or are planned for the future in the Columbia River Basin: conventional hatcheries, supplementation hatcheries, and genetic conservation hatcheries (captive broodstock programs).
The primary objective of conventional hatcheries is to maximize surplus adult production for harvest while minimizing straying impacts on natural populations. Although conventional hatcheries have come under extreme criticism recently, it is not likely that the magnitude of conventional production will be reduced substantially in the near future. Society's expectations for traditional tribal, commercial, and recreational fisheries have not diminished, and thus the demand on conventional hatcheries to support fisheries has not changed appreciably. It is, therefore, important to continue to seek knowledge to answer genetic questions associated with conventional hatcheries (Table 1).
Table 1.
· Summary of genetic questions associated with conventional hatcheries, which have the primary goal of producing maximum surplus adults for harvest benefits.
· If a hatchery stock has demonstrated consistently high performance and has been perpetuated under good genetic guidelines, is there any benefit to infusing natural fish?
· What should we do with hatchery stocks that are performing poorly--start over, infuse local natural fish, or infuse another hatchery stock?
· What percentage of nonlocal hatchery strays in a natural population is too high?
· Will the effect of straying vary with genetic similarity, and is some level of straying beneficial?
· How can we best assess genetic well-being of existing hatchery stocks?
· Should we utilize selective breeding to compensate for known selective harvest and mortality?
· Is there a recommended relationship between broodstock numbers and mating strategies (pooled, singlecross, or split-cross matrix)?
Anadromous salmonid stocks in the Columbia River Basin have shown severe declines in numbers and productivity as a result of habitat alterations in the mainstem migratory corridor and tributary production areas. In response to depressed population levels, managers have planned or initiated a substantial number of hatchery supplementation projects designed to enhance natural production through artificial propagation. Genetic risks and uncertainties associated with supplementation programs are considerably greater than those associated with conventional hatcheries because of the intentional introgression of hatchery fish into natural populations. Because of higher levels of risk and uncertainty associated with supplementation hatcheries, a majority of the questions fell into this category (Table 2).
Table 2.
Summary of genetic questions associated with supplementation hatcheries, which have the primary objective of enhancing natural production.
What is the best course of action when a population is depressed, declining, and at risk of extinction if the causes of depression cannot be relieved:
When initiating a supplementation program with natural fish:
Regarding management of hatchery broodstock and natural escapement when hatchery fish return:
What are the least risky supplementation strategies--heavily for a short time or lightly for a long time?
Should we be concerned with family size variation? If so, how should we manage it?
Does the hatchery environment select for maladaptive genes or gene complexes that affect the ability of hatchery-reared fish to perform in nature?
Is some level of domestication selection needed before a hatchery stock that is developed from natural fish will perform well in the standard hatchery environment?
If we are able to develop hatchery environments that are more natural, will that reduce the need for domestication?
How does genetic variability relate to stock viability, and how much within- and between-stock variation is needed?
Can we assess loss of genetic diversity and rates of introgression between populations?
What is the functional meaning of genetic distance in terms of stock compatibility or similarity? Can genetic distance be used in selecting a donor stock for supplementation?
Given that we have altered and continue to alter environments at rapid rates, should we maximize genetic variability of hatchery populations or attempt to mimic genetic structure of the target wild population?
What are the risks associated with selective breeding designed to increase abundance of specific life history types?
Does outbreeding depression occur in natural populations as a result of natural straying?
Can we quantify the risks of inbreeding depression for severely depressed populations and use inbreeding risk in our decisions whether to supplement?
Genetic conservation hatcheries (or captive broodstock programs, which involve captively rearing fish through an entire life cycle) have the primary objective of preserving genetic resources for reintroduction into nature when suitable habitat is restored. Such programs were not utilized for anadromous salmonids in the Columbia River Basin until the Redfish Lake (Idaho) sockeye salmon (O. nerka) program was initiated in 1991 following its listing as an endangered species under the U.S. Endangered Species Act. I anticipate that additional captive broodstock programs will be proposed and developed for Chinook salmon stocks in the Snake River Basin. The extended length of captivity and small initial population sizes typically associated with captive broodstock programs result in additional risks and uncertainties beyond those described for supplementation hatcheries (Table 3).
Table 3.
The number, complexity, and diversity of questions is immense and the need for genetics information is increasing rapidly. Genetics has become a focus in fisheries management in the Columbia River Basin; therefore, managers have high expectations for specific genetic information and guidance. Most of the questions described here cannot be answered in a short time period, and it is clear that laboratory data alone will answer few, if any, of the critical questions. There is a need to develop cooperative investigations that integrate laboratory studies with natural production, life history, and demographic studies. Change in management philosophy and direction comes slowly, and quantitative data are essential because it is difficult to make major changes based solely on theory. The more often we can demonstrate the management benefits of implementing sound genetic principles and guidelines, the easier implementation will become.