Precocial maturation of male sockeye salmon in the Fraser River, British Columbia, and its relationship to growth and year-class strength

We analyzed historical data on the age structure and abundance of males in 22 populations of sockeye salmon (Oncorhynchus nerka) in the Fraser River, British Columbia, to determine geographical and temporal patterns of precoc ial maturation, its relationship with growth and maturation at other ages, and the value of precocial males as indicators of year-class strength. Most Fraser sockeye males spend two winters at sea before maturing at 3-5 years of age. Precocial males return to spawn at 2, 3, or 4 years of age (ages 0 .1, 1.1, and 2.1) and comprised <1 to > 33% of male brood year returns amon g populations. Precocity was lowest among populations that spawned far upst ream and highest among populations spawning to the west of the main Fraser River and was not correlated with migration distance. Precocial maturation was related to growth during the second summer in the ocean to brood line a nd to brood line abundance. The combination of brood line, abundance, and s ize of precocial males accounted for more than 75% of the variation in tota l returns in four populations, suggesting that these variables might be use d to predict abundance 1 year in advance.