Fixed exploitation rate strategies for coping with effects of climate change

Survival rates and carrying capacities for larval and juvenile fishes may be strongly affected by long-term, unpredictable climatic fluctuations. When climate impacts produce strongly autocorrelated interannual variations in recruitment, harvesting a constant fraction of the stock each year allows the spawning stock to track such variations. Dynamic programming analysis indicates that this tracking effect is likely to produce long-term harvests that are very close (within 15%) to the theoretical optimum that could be achieved if all future climatic variations were known in advance. Fixed harvest rate strategies are likely to degrade performance more than 10% only when there is little interannual correlation in environmental effects or when there is a large, abrupt climate change that can be predicted well in advance if it is going to increase carrying capacity, or detected immediately if it causes a decrease in capacity. This finding implies that it may be more cost effective to invest in research on how to implement fixed harvest rate strategies than to invest in research on explaining and predicting climatic effects. Successful implementation may require a combination of improved stock size assessments, and stringent regulatory measures to substantially restrict the proportion of fish at risk to fishing each year.