The impact of alternative rebuilding strategies to rebuild overfished stocks

摘要

Ending overfishing and rebuilding fish stocks to levels that provide for optimum sustainable yield is a concern for fisheries management worldwide. In the United States, fisheries managers are legally mandated to end overfishing and to implement rebuilding plans for fish stocks that fall below minimum stock size thresholds. Rebuilding plans should lead to recovery to target stock sizes within 10 years, except in situations where the life history of the stock or environmental conditions dictate otherwise. Federally managed groundfish species along the US West Coast have diverse life histories where some are able to rebuild quickly from overfished status, while others, specifically rockfish (Sebastes spp.), may require decades for rebuilding. A management strategy evaluation which assumed limited estimation error was conducted to evaluate the performance of alternative strategies for rebuilding overfished stocks for these alternative US West Coast life histories. Generally, the results highlight the trade-off between the reduction of catches during rebuilding vs. the length of rebuilding. The most precautionary rebuilding plans requiring the greatest harvest reduction resulted in higher average catches over the entire projection period compared with strategies that required a longer rebuilding period with less of a reduction in rebuilding catch. Attempting to maintain a 50% probability of rebuilding was the poorest performing rebuilding strategy for all life histories, resulting in a large number of changes to the rebuilding plan, increased frequency of failing to meet rebuilding targets, and higher variation in catch. The rebuilding plans that implemented a higher initial rebuilding probability (>= 60%) for determining rebuilding fishing mortality and targets generally resulted in fewer changes to the rebuilding plans and rebuilt by the target rebuilding year, particularly for stocks with the longer rebuilding plans (e.g. rockfishes).