In commercially exploited, long-lived fish species, age structure plays an important role in population stability and resilience to human and environmental impacts. Reduction in the relative abundance of older age classes due to fishing is a necessary consequence of exploitation, which will be exacerbated if selection is focused on the largest fish. Consequences of the reduced abundance in older age classes include increased population variability perpetuated through increases in recruitment variability, as well as changes in demographic parameters, such as the growth rate, that lead to unstable, non-linear, population dynamics. Older females of long-lived species can contribute to population stability through an increase in both the quantity and quality of larvae, and by more variable spawn timing and locations. An increase in energy allocation per offspring can improve larval survival through an increased time to starvation and higher likelihood of encountering favorable environmental conditions once released. In this study I asked two primary questions: (1) within the existing management framework for west coast rockfishes, can constraints on selectivity and adjustments to the status quo control rule enhance age structure, and (2) what are the impacts of these alternative strategies on yield and stock productivity?
Linsey Arnold, Department of Fisheries and Wildlife, Oregon State University