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ABSTRACT: Because of the decline in harvestable yield of Dungeness crab (Cancer magister) in the San Francisco area since 1961, a study has been undertaken to determine critical stages in the crab’s life history and environmental factors affecting survival.
All larval stages except the 5th zoeal have been collected in the ocean off San Francisco January through March 1975-76, megalopae in the San Francisco-San Pablo Bay-complex in April and May 1975-76, and first post-larval crabs in San Pablo Bay in May 1975-76. Eighty percent of 1975 year-class crabs entered the Bay-complex to use it as a nursery ground. Staghorn sculpin, starry flounder, big skate, and brown smoothhound were the principal fish predators on megalopae and juveniles. Multi-variate correlations comparing crab landings with an array of oceanographic parameters and the crab density dependent factor show that from March through May, when late stage larvae prevail, the most significant correlating factors were sea level and atmospheric pressure for central California and, for northern California, the density dependent factor and sea surface temperature. Analyses of crab tissues for contaminants revealed petroleum hydrocarbon burdens, Ag, Se, Cd, and PCB's higher in central California crabs, while DDE was found in higher amounts in northern California crab tissue.
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