Changes in the productivity of US West Coast fish stocks

The California Current ecosystem is highly dynamic at interannual to interdecadal time scales. Variability has been documented in pelagic and other fish species, but climate change may be altering the historical models of variation. This study investigates changes in productivity of 31 fish stocks in the California Current ecosystem. Productivity was measured from recent stock assessments, as the per-capita recruitment rate, estimated with a dynamic stock-recruitment model. Contrary to expectations, the dynamic stock-recruitment model fit better than the corresponding stationary model for only seven of the 31 stocks. There was little evidence of linear drift in productivity that might be expected to result from climate change. Climate variables improved forecast accuracy for a few stocks, but there was no common climate signal in productivity. One explanation of these results is that most of the west coast stocks are above their biomass levels for maximum sustainable yield, making them less susceptible to environmental variation. On the other hand, the dynamic recruitment models improved short-term forecasts for all stocks, which may be useful for quota setting. Finally, results for the subset of stocks with dy-namic recruitment models could be used to establish dynamic biological reference points.