Comments: Because of the fixed two-year life cycle, individuals spawning in a particular river system in odd and even years are reproductively isolated from each other and have developed into genetically different lines; in some river systems, such as the Fraser River in British Columbia, only the odd-year line exists in significant numbers; in Bristol Bay, Alaska, the major runs occur in even years (areas in between have runs in both even and odd years) (Heard 1991). An electrophoretic study by Varnavskaya and Beacham (1992) found that "pink salmon from the Fraser River and southern British Columbia were distinct from more northerly spawning populations in British Columbia, Alaska, and Kamchatka. The concept of a 'fluctuating stock' population structure of pink salmon or ramdom mixing during spawning over a large geographic area was not supported by observed patterns of genetic variation." In Russia, in contrast, lack of distinct stocks in different areas has been inferred from the lack of biochemical genetic differention detected in some surveys (see Varnavskaya and Beacham 1992).
Has hybridized with chinook salmon in the St. Marys River, Michigan (Rosenfield 1998).
Phylogenetic analysis based on mtDNA data indicates a sister relationship between pink salmon and chum salmon (Domanico and Phillips 1995).