ABSTRACT
Two isolated populations of pink salmon (Oncorhynchus gorbuscha) spawn in odd- or even-numbered years in Auke Creek, Alaska, and many other streams bordering the subarctic Pacific Ocean. We have used a series of breeding experiments to analyze variation of life history traits in those populations, and to test for outbreeding depression in F2 hybrids between them. Analysis of between family variation of embryonic traits (studied in the laboratory) and of adult traits (in fish liberated to sea and returning as adults to their natal stream) provides evidence of genetic variation of date of return, body size, fecundity, embryo development time, etc. Genetic variation of survival itself was high particularly when cohort survival at sea was high. Genotype by environment interaction was evident in our analysis of variation of embryo development time under different environmental (temperature) regimes. Outbreeding depression (reduced survival at sea in the second generation) was suggested in hybrids (formed by cryopreservation of semen) between sympatric Auke Creek populations, odd-year and even-year salmon. This evidence supports the notion that differences between local populations of salmon have evolved in response to selection in different local environments and that genetic variation.