Determination of Independent Populations and Viability Criteria for the Hood Canal Summer Chum Salmon Evolutionarily Significant Unit

摘要

The Puget Sound Technical Recovery Team identified two independent populations of summer chum salmon (Oncorhynchus keta) within the Hood Canal Summer Chum Salmon evolutionarily significant unit (ESU), which is listed as threatened under the U.S. Endangered Species Act. Our analysis was based on allozyme and microsatellite DNA variation, straying patterns, historical and present geographical distribution, and life history and ecological variations. Based on multiple lines of evidence, we concluded that the ESU contains two independent populations. The Strait of Juan de Fuca population spawns in rivers and streams entering the eastern Strait of Juan de Fuca and Admiralty Inlet. The Hood Canal population includes all spawning aggregations within the Hood Canal watershed. An analysis by state and tribal biologists in 2000 identified three extant stocks associated with the Strait of Juan de Fuca population and six extant stocks associated with Hood Canal population. However, we considered spawning aggregations to be independent populations only if the aggregations were isolated to such an extent that exchanges of individuals among the aggregations would not be expected to substantially affect the population dynamics or extinction risk of the different groups over a 100-year time frame.