ESTIMATED PRESEASON ABUNDANCE IN THE CALIFORNIA DUNGENESS CRAB (CANCER-MAGISTER) FISHERIES

Annual preseason abundance for the central and northern California dungeness crab (C. magister) fisheries is estimated from the decline in catch per unit of effort (CPUE) within each fishing season. A large fraction of the available, legal size, male crabs are harvested each year; regular changes in this fraction were noted and it is rarely as high as previously assumed. In central California [USA], annual exploitation rate was 92% during 1951-1956 and declined to 72% following the collapse of the fishery. In northern California, the annual exploitation rate varies with the 10-yr cycle of catch: 69% during the last few high catch years of each cycle, 84% in the 1st low catch year, and 54% during remaining low catch years and the 1st high catch year. The 2nd high catch years are exceptions to a high exploitation rate. CPUE was saturated (i.e., did not decline) throughout the 1957 and 1977 fishing seasons. The large size of male crabs in the 3rd and 4th high catch years also indicates high escapement in the 2nd high catch years. Individual year-classes apparently may dominate the fishery for several years. The time series of population abundance and recruitment is not as smoothly cyclic as the catch record.