Factors that contribute to the ecological risks of salmon and steelhead hatchery programs and some mitigating strategies

Abstract

State and federal agencies in the United States annually release millions of hatchery salmon and steelhead into public waters. Many of the hatchery programs are located in areas where the wild populations are now listed under the U.S. Endangered Species Act (ESA) (16 U.S.C.§ § 1531-1544). These hatchery programs pose genetic and ecological risks to wild fish populations. Genetic risks occur when hatchery and wild fish interbreed and usually occur within a taxonomic species. Ecological risks occur when the presence of hatchery fish affects how wild fish interact with their environment or with other species and may affect whole species assemblages. This paper reviews some of the factors that contribute to ecological risks. Important contributing factors include the relative abundance of hatchery and wild fish in natural production areas, hatchery programs that increase density-dependant mortality, residual hatchery fish, some physical advantages that hatchery fish can have over wild fish, and life history characteristics that may make some species especially vulnerable to the effects of ecological risks. Many of these risk factors can be mitigated by management activities that reduce the level of interactions between hatchery and wild fish. This paper concludes by recommending twelve mitigation strategies that may be useful when agencies need to bring hatchery programs into compliance with the take provisions of the ESA.

Effective size of a wild salmonid population is greatly reduced by hatchery supplementation

“…We have DNA samples from all broodstock, and comprehensive records on broodstock pairings in the hatchery. Extensive details on this study system, management practices, steelhead life-history and reproductive success can be found elsewhere (Olsen, 2003;Araki et al, 2007a,b;Kostow, 2009).…”

“…Steelhead trout, Oncorhynchus mykiss, are typical of most Pacific salmonids in that their declining populations have led to the creation of numerous supplementation programs (Kostow, 2009). In this study, we examined 12 run-years of steelhead from Hood River, Oregon for which all anadromous fish were genotyped at eight highly polymorphic microsatellite loci.…”

Genetic adaptation to captivity can occur in a single generation

“…Billions of captive-reared salmon are intentionally released into the wild each year in efforts to increase fishery yields, mitigate environmental disturbances, and bolster severely declining populations (17)(18)(19). Steelhead from the Hood River in Oregon are listed as threatened under the US Endangered Species Act (20), and part of their recovery plan includes supplementation with juvenile fish produced in a captive breeding program (i.e., fish hatchery).…”

Columbia River Hatchery Reform System-Wide Report.

“…For example, competition between hatchery and natural steelhead juveniles in the Columbia River Basin is of concern to the HSRG, with adverse effects on the natural population having been documented (e.g., Kostow 2008). The concern is that although hatchery steelhead may compete effectively at the juvenile stage, they appear to have inferior reproductive success.…”