Analysis of contemporary genetic structure of even-broodyear populations of Asian and western Alaskan pink salmon , Oncorhynchus gorbuscha

Pink salmon (Oncorhynchus gorbuscha) are the most abundant Pacifi c salmon species and spawn along most of the Pacifi c rim coastline north of 40°N latitude (Heard, 1991). The species is unique among salmonids in having a determinate life cycle. Adults return to their natal streams to spawn at 2 years of age, which has resulted in separate broodlines in even and odd years (Heard, 1991). Most of the range supports spawning runs of both broodlines, although they may differ in numbers. The southern part of the North American Pacifi c coast has only small even-year runs; and in western Alaska, even-year runs are much more abundant than odd-year runs (Heard, 1991). The pattern of a numerically dominant broodline in many areas has changed since early this century, perhaps in response to changes in fi shing intensity (Takagi et al., 1981) or climate cycles (Mantua et al., 1997). Optimum management and conservation of the pink salmon resource requires thorough knowledge of their biology, including population structure, relationships among populations, and the extent of genetic exchange among local populations and between geographically distinct regions. Genetic divergence among groups of salmon also may provide a basis for stock identifi cation by fi sh managers (Beacham et al., 1985; Pella and Milner, 1987). Although DNA-based analyses have become available in recent years (e.g. Park and Moran, 1994), allozyme analAnalysis of contemporary genetic structure of even-broodyear populations of Asian and western Alaskan pink salmon, Oncorhynchus gorbuscha