Expected Changes in Stock Recruitment Parameters When Exploiting Mixed Stocks of Salmon

The parameters for a Ricker stock recruitment relationship can change due to a number of factors. Methods for distinguishing between habitat elimination, lowered brood success, and elimination of less productive substocks are discussed. Data for the Columbia River Fall Chinook, and Skeena River Sockeye are analyzed in light of these considerations. It is also shown that the expected changes in productivities are strongly affected by the correlation of productivities of the different substocks. The importance of the above factors are discussed in relation to proposed enhancement facilities.