Science Advisory Report 2008/021

Recovery potential assessment for the Okanagan population of chinook salmon (Oncorhynchus tshawytscha)

Summary

• Okanagan Chinook were designated as threatened by COSEWIC in April 2006.
• The peak count of Okanagan Chinook spawners since 1977 was 35 in 2006. The next highest count was 29 in 2005.
• Three alternative hypotheses have been put forward to explain the degree of isolation and uniqueness of the population: 1) Okanagan Chinook are demographically isolated and ecologically non-exchangeable, 2) they are demographically isolated but ecologically exchangeable, and 3) they are not demographically isolated and they are ecologically exchangeable with U.S. Chinook in the Columbia River system.
• Okanagan Chinook are genetically similar to other upper Columbia River stocks such as the Similkameen stock.
• The level of allelic diversity in the Okanagan population is not indicative of a small inbred population, but instead they appear to have the same level of genetic diversity as seen in the larger U.S. population. This supports the conclusion that there is gene flow from the larger population and the Okanagan population is not genetically isolated.
• The weight of evidence indicates that the existing Canadian population is maintained in part by strays from the U.S. population and that rescue from this larger population is possible.
• A demographically isolated spawning population of Chinook can not be maintained without large-scale hatchery augmentation due to the high mortality rate associated with U.S. dams.

Complete document (PDF, 117 KB)

Accessibility Notice

This document is available in PDF format. If the document is not accessible to you, please contact the Secretariat to obtain another appropriate format, such as regular print, large print, Braille or audio version.