Changes in the long-term distribution of commercially caught Cowichan chinook

Abstract

The Cowichan River, British Columbia (BC), Canada stock of Chinook Salmon (Oncorhynchus tshawytscha) is used federally in Canada, as an escapement indicator of the Lower Georgia Strait (BC) Chinook and as such is important both locally and internationally as part of the Pacific Salmon Treaty. The study examines the changes in distribution of catch of Cowichan hatchery Chinook from 1977-2011, using coded wire data. Regression analysis of SST and percentage of total catch when looked at by regime revealed different strengths of correlation for different areas. Statistically significant results occurred more often in the highly productive Regime 1 (1977-1988) for the west coast of Vancouver Island. SST one year prior to catch showed correlations to catch distribution more frequently than when compared to SST at brood year, sea entry year, or catch year. These population specific results can be compared to other populations to help tailor decisions around changing population dynamics in order to best manage stock-specific fisheries.