Growth and reproductive dynamics of adult female Dungeness crabs (Cancer magister) in northern California

Abstract

A total of 12034 adult female Dungeness crabs ranging in carapace width from 91.6 to 172.9 mm were tagged and released in northern California waters. A molt increment regression line, based on 111 single- molt tag recoveries and 166 laboratory molting records, showed that average molt increments declined linearly from about 21 to 12 mm as carapace widths increased from 90 to 150 mm. Size-specific annual molting probabilities, estimated from shell-condition data, exceeded 0.90 for crabs with carapace widths less than 135 mm but then declined rapidly to near zero at carapace widths exceeding 160 mm. Estimated annual survival rates averaged 0.11 for crabs exceeding 155 mm; survival rates for smaller crabs are probably greater, but could not be estimated. Tag-recovery data provided evidence that most adult females extrude egg masses annually, but that many do so without molting and mating; viable sperm may be retained for at least 2.5 years. Size-specific fecundities ranged from about 0.1 to 1.6 million eggs and were found to depend on previous molting history as well as on crab size. For individuals of similar size, crabs that had molted during the most recent season had greater fecundities than those that had not.