Recovery of the Bristol Bay stock of red king crabs under a rebuilding plan

摘要

After peak landings in 1980, the red king crab fishery in Bristol Bay (Alaska) was closed in 1983 because of stock collapse. In the follow-ing decade, small commercial harvests and additional fishery closures (1994 and 1995) associated with depressed stock status prompted a reappraisal of the management strategy. A length-based population model was developed, which provided an improved stock assessment for setting annual catch quota. A management strategy evaluation revealed that a harvest strategy, which included a stair-stepped harvest rate of 10-15% of mature males and a threshold for effective spawning biomass below which no fishing is per-mitted, provides for relatively high long-term yield, greater stability in yield, fewer fishery closures, and higher effective spawning biomass. This strategy was adopted in 1996, in addition to crab bycatch caps and closed areas, to protect sensitive crab habitats implemented in the management of the groundfish trawl fishery. Since then, abundance of legal-sized males increased by 58%, that of mature males doubled, and mature female abundance and effective spawning biomass tripled through 2008. The stock has been considered rebuilt since 2003. Subsequently, a sharp reduction in fishing capacity improved profitability of the fishery, after implementation of an individual fishing quota programme in 2005.