Population genetics, conservation and evolution in salmonids and other widely cultured fishes: some perspectives over six decades
Abstract:This paper explores my shifting understandings of interactions primarily between salmonid fish culture and fish conservation during the latter half of the 20th century. The idea that conspecific natural and cultured fish were largely interchangeable among phenotypically similar populations began to change with the advent of molecular genetic markers. With the gradual clarification of major geographic lineages beginning in the 1970s came awareness that translocations among anadromous lineages were generally destined for failure; in contrast, gene flow more readily occurred among non‐anadromous lineages and sometimes, species. Concurrently, data were accumulating that adaptations to their respective environments distinguished cultured and wild populations within a lineage. Reduced obstacles to gene flow at this level often resulted in homogenizations among wild and cultured fish in areas where widespread hatchery releases occurred; conversely, adaptive radiations in vacant habitats sometimes occurred over a few decades from single source hatchery releases. Current ideas relating to salmonid interbreeding, population substructure and culture germinated from these observations. Among lineages, resistance to gene flow is much greater between anadromous than purely freshwater populations or species. Ease of within‐lineage gene flow in both groups is problematical with regard to cultured and wild populations because large‐scale supplementation programs erode local adaptations and fine‐scale population substructures. A potential ability to regenerate natural substructure upon relaxation of supplementation is offset by uncertainties of time scales and intrinsic capabilities homogenized populations. However these losses can be minimized by a management that separates harvest and reproduction of wild and cultured subpopulations. Some generality of this strategy to other fishes is supported by losses of local adaptations and outbreeding depression in black basses following population admixtures that parallel those observed in salmonids.
Document Type: Research Article
Affiliations: School of Aquatic and Fishery Sciences, University of Washington, Box 355020, Seattle, WA 98195 U.S.A.
Publication date: 2004-12-01