Commercial salmon aquaculture has demonstrated explosive economic growth and a potential to supply demands for salmon that exceed wild production capacity. But it has
Also raised a suite of concerns for wild salmon populations, including genetic, ecological and disease- related issues. It is important to realize that the three interests (wild fish, capture fisheries and fish farming) are all competing over the same salmon ecosystem·
One source of impact is the mixed-stock fishery, where harvest of wild stocks is over-inflated due to the presence of hatchery stocks. Other significant concerns include the behavioral, morphological and genetic changes in hatchery fish that result from captive breeding. For example, when reared in hatcheries, individuals lack information about predators, food sources and habitat structure, have altered morphologies, and undergo genetic changes associated with sampling and selection in the hatchery environment. All of these changes reduce the performance of hatchery-bred salmon in the wild.
Hatchery salmon, particularly males, are competitively inferior to wild males. Behavioral and DNA fingerprinting studies show that they are denied access to ovipositing females, partake in fewer spawnings, hold more distal positions in spawning hierarchies, and may attain only 46% of the breeding success of wild males.
Hatchery females suffer greater delays in the onset of breeding, fail to spawn as many eggs, lose more eggs to nest destruction by other females, and may attain only 82% of the breeding success of wild females. However, even with reduced reproductive success, the large numbers of released hatchery individuals relative to their wild counterparts can alter the gene frequencies of a population, replacing wild adaptations with domestic adaptations to the hatchery. In addition there are now indications that, in mixed populations, hatchery fish decrease effective population size an important measure of individual genetic contribution, relative to wild and wild hatchery populations. Thus, supplementation of wild populations with captive-bred hatchery fish may be a larger conservation concern than is generally realized.
In recent years, the growing awareness of impacts resulting from production hatcheries has prompted proposals for dual-role conservation hatcheries that would serve for both fishery augmentation and biodiversity preservation (e.g., living gene banks). Unfortunately, the protocols for conservation hatcheries that might prevent loss of genetic quality and divergence of hatchery fish from wild fish are yet to be fully developed or tested.
·genetic diversity is for future evolution, genetic quality is for adaptation in the present, which gives populations their population size and resilience.
On-going experiments suggest that female mate choice may be important in maintaining genetic quality of offspring through female choice for males with good genes or complementary genes. Current genetic protocols in hatcheries do not incorporate such female mate choice. This suggests that conservation hatcheries are only experiments in progress and not yet fully functioning tools for biodiversity protection.
SUMMARY:
Hatchery reform requires clearly identifying what hatcheries are for (goals), determining if these goals are defensible (cost:benefit analysis), conducting empirical research to fill the holes in the cost:benefit analysis, explicitly dealing with uncertainty (risk analysis), and creating an integrated management plan (other stakeholder goals). An integrated and comprehensive, coast-wide and interior, fisheries management plan is necessary for reducing conflict among stakeholders. The plan must recognize the legitimacy of multiple users·