Fisheries-induced evolution of alternative male life history tactics in Coho salmon.

Fisheries-induced evolution (FIE) can result when harvest imposes artificial selection on variation in heritable phenotypic traits. While there is evidence for FIE, it remains difficult to disentangle the contributions of within-generation demographic adjustment, phenotypic plasticity, and genetic adaption to observed changes in life history traits. We present evidence for FIE using dozens of Coho salmon () populations in which males adopt one of two age-invariant, heritable life history tactics: most mature as large three-year-old "hooknose" and typically fight for spawning opportunities, while some mature as small two-year-old "jacks" and fertilize eggs through sneaking.