An Evaluation of the Variability of Groundfish Populations off the Coast of Alaska

There is a growing recognition that the long-term effects of fishing could contribute to increased variability in recruitment.  This paper examines two potential mechanisms linking fishing to recruitment variability: (1) fishing results in the juvenation of the spawning population which increases the variation in annual spawning output due to greater dependence on incoming year-classes of maturing fish,  (2)  fishing reduces the mean age of the spawning population thus reducing the number of experienced spawners that produce more viable young, this results in eggs and larvae that are more vulnerable to natural mortality in the early life stages.  The alternative hypothesis is that observed trends in recruitment variability result from natural variations in the ecosystem.  This paper reviews the time trends in the age composition, size composition, and recruitment variability groundfish stocks off the coast of Alaska relative to time trends in fishing mortality and natural variability.  A key question is whether current harvest strategies provide sufficient protection of the reproductive potential of the stock to guard against the expression of fishing induced impacts on recruitment.  The groundfish stocks off the coast of Alaska have been managed in a precautionary way for several decades and thus it is expected that evidence of fishing induced trends in recruitment variability would be less evident in these populations.