Cooperative Fish and Wildlife Research Units Program: Washington
Education, Research and Technical Assistance for Managing Our Natural Resources

Much of the historical abundance and diversity of Chinook salmon (Oncorhynchus tshawytscha) and steelhead trout (O. mykiss) have been lost in the Interior Columbia River, which led to the listing of many populations under the Endangered Species Act. Recovery goals have not been achieved despite substantial efforts, and there is a need to better understand the effect of various threats and ecosystem drivers on population dynamics. Three factors are of particularly high interest: 1) the effect of the quality of freshwater habitats used for egg incubation and juvenile rearing; 2) the effect of broad-scale ocean conditions on marine survival; and 3) the effect of predation by marine mammals. To characterize how these factors affect population viability, we will develop an integrated population modeling framework for spring-summer Chinook salmon by combining count and mark-recapture data. In this approach, data streams related to survival or productivity will be integrated with data streams related to abundance to estimate demographic parameters with greater statistical precision and less bias than would otherwise be possible. These models will use previously collected data to characterize the role of freshwater habitat, ocean conditions, and marine mammal predation on the abundance, productivity, diversity, and viability of salmon and steelhead populations in the Interior Columbia River. This research will facilitate evaluation of the benefits of past habitat restoration actions, will support decisions about future actions, and will provide an assessment of population viability.