Spatial recruitment patterns in Bristol Bay (Alaska) red king crab: The roles of climate and larval advection

Abstract

The red king crab (Paralithodes camtschaticus) stock in Bristl Bay once supported the most lucrative fishery in the world, but catches over the last ~20 years have been substantially reduced compared to late 1970s levels.  Since the collapse of the stock the fishery has been closely managed and harvests have been maintained within strict guidelines.  However, these actions have had little effect on stock rebuilding, suggesting that factors outside the fishery may be exerting strong influence on overall population abundance.  We hypothesize that the population is regulated by the survivorship of early post-settlement stages that require complex substrates as nursery habitat, and that presently low recruitment levels are in part the result of climate-forcing that has altered larval source-sink dynamics in the stock.

During the 1980s, a shift occurred in the mature female distribution: once found predominantly near Unimak Pass, most broodstock is presently located farther to the northeast, north of Port Moller.  We hypothesize that the shift in broodstock distribution may have represented a response by females to their thermal environment and present evidence that altered broodstock distribution was accompanied by changes in spatial recruitment patterns.  Recruitment to southern regions of Bristol Bay, which predominated in the 1970s, is apparently rare at present, and the stock appears more reliant upon nurseries in the Kvichak and Togiak regions.  These observations are consistent with larval advection modeling that suggests little ability for present broodstock distributions to seed southern nurseries with competent settling-stage larvae.