SALMON BREEDING-BEHAVIOR AND LIFE-HISTORY EVOLUTION IN CHANGING ENVIRONMENTS

Male salmon have two life-history tactics: maturing precociously at a small body size, or delaying maturity until a larger body size is reached. Conditional strategies permit rapid responses as alternative life-history and behavioral tactics are expressed. Many human activities in the ocean and salmon breeding environment can be expected to elicit long-term evolutionary changes in the proportion of male coho salmon Oncorhynchus kisutch maturing as jacks. Other activities in freshwater rearing environments will have short-term effects. In some cases, male salmon populations once characterized by fighting hooknose males may instead become characterized by smaller precocious jacks. It is also possible that ocean-caught salmon will someday be females only. -from Author