Intrinsic and environmental drivers of growth in an Alaskan rockfish: an otolith biochronology approach

Otolith growth-increment chronologies provide an approach for evaluating the impacts of both high-frequency (e.g., interannual) and low-frequency (e.g., interdecadal) climate variability on fish growth. A growth-increment biochronology spanning six decades, spanning several warm and cold climate regime periods, was developed for a commercially important species of rockfish, Sebastes polyspinis, in the Gulf of Alaska. To confirm that all increments were correctly identified and placed in time, we borrowed the technique of crossdating from the tree-ring science of dendrochronology, which ensured high data quality. We then used a mixed effects model to partition variance in otolith growth-increment width among intrinsic (e.g., age-related) and extrinsic (e.g., climate-related) factors. This biochronology was contrasted with one recently developed for S. alutus, a closely-related species which exhibited a significant change in growth following the late 1970s North Pacific climate regime shift. Both species generally showed positive relationships between warm climate conditions and growth, though S. polyspinis experienced a relatively smaller step-increase in growth following the regime shift. The new S. polyspinis otolith biochronology represents a long-term record of growth that extends well before biological specimens were first collected in the Gulf of Alaska, providing a potential tool for fisheries managers to evaluate the effects of climate variability on growth and biological reference points.