A model for the processes regulating recruitment for a sockeye salmon stock

Abstract

Recruitment relationships are a central issue in the management of sockeye salmon ( Oncorhynchus nerka ) but when these relationships are fitted, they have almost never been statistically significant and their underlying mechanisms have never been demonstrated. In contrast, the model presented here is significant at least at the α = 0.05 level and is based on mechanisms which have been described in the literature. The Chilko Lake stocks (Fraser River system, British Columbia) exhibit resource limitation during fry migration and a Ricker-type compensatory relationship due to density-dependent growth and subsequent size-dependent mortality. Modeling resource limitation and Ricker's curve accounts for 79.5% of the total variation in the number of smolts emigrating from the nursery lake and the number of emigrating smolts accounts for 71.0% of the total variation in the number of adults recruiting to the fishable population. Depensatory mortality during smolt migration together with weak compensation account for an additional 9.1% of the variation. Thus, 80.1% of the total variation is accounted for. The remaining 19.9% is probably mostly measurement error.