Nearly a half century of high but sustainable exploitation in the Dungeness crab (Cancer magister) fishery

Abstract

The fishery for Dungeness crab (Cancer magister) is one of the largest and most valuable on the US West Coast. Though conventional wisdom holds that the fishery takes the large majority of legal-sized male crab coast-wide each year, this has not been demonstrated analytically. We use catch and effort data and a Bayesian depletion estimator to estimate pre-season abundance of the coastal population of legal-sized male Dungeness crab from 1970 to 2016 (California) or 1982–2016 (Oregon and Washington) and estimate that the fishery takes 9 %–98 % of the legal-sized male population each year, averaging 66 %. The percent taken has increased over time in all areas. We find that although fish tickets (landing receipts) have limited information on fishing effort, they lead to similar estimates of abundance compared to the more detailed logbook data. Fish ticket estimates of abundance tend to be slightly lower than logbook estimates. Logbooks also show evidence that catchability is time-varying or density-dependent (i.e., catch rates exhibit hyperdepletion), which is not evident in the fish ticket data. Pre-season abundance of legal-size males appears to be stable or increasing in all areas over the period considered in spite of the high rate of exploitation and large year-to-year fluctuations. In Central California, pre-season abundance has shown a particularly rapid increase during the past decade after a long period of low abundance, likely due to changing oceanographic conditions.