Managing fisheries using genetic data: case studies from four species of Pacific salmon

Abstract

Pacific salmon exhibit complex patterns of population subdivision and undergo substantial marine migrations that result in stock intermixing. Stock assessment, fishery management, and conservation of salmon are all complicated by stock multiplicity and intermingling in fishing areas. Genetic data have been successfully used by several agencies in the Pacific Northwest for over a decade to address assessment, management, and conservation needs. Four case studies are described to document the design, implementation, results, and benefits of genetic analysis. These consist of: (1) the chinook salmon winter gill-net fishery in the lower Columbia River (allozymes), (2) commercial pink salmon fisheries in British Columbia (allozymes), (3) chum salmon fisheries in Alaska (allozymes, mtDNA, and microsatellites) and, (4) the recreational coho salmon fishery off Vancouver Island (microsatellite and MHC genes). Estimates of stock group and/or individual stock contributions to harvests are obtained using maximum likelihood methods. Simulations indicate that estimates are often within 5–10% of the true contributions and are quite precise (±2–10%) with sample sizes of 100–400. Genetic results have been used both in-season and post-season to determine fishery openings and closures to provide harvest benefits or meet conservation needs, to address catch allocation and equity issues among user groups and between countries, to provide data for in-season run-size updates, and to investigate migration patterns and timing.