Dungeness crab research program: report for the period January 1 - August 31, 1979

Farley, Timothy A. (1979) Dungeness crab research program: report for the period January 1 - August 31, 1979. Sacramento, CA, California Department of Fish and Game, Marine Resources Region, (Marine Resources Administrative Report, 79-16)

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Abstract

The central California Dungeness crab, Cancer magister, resource experienced its 18th successive season of very low harvestable yield. Plankton sampling efforts were concentrated on late stage larvae and megalopae. The 1979 year-class developed during a period of relatively cold oceanic water, particularly when compared with the previous year. Hatching probably occurred during the first 2 weeks in January. Small quantities of early stage zoeae were found in the Gulf of the Farallones in January, but were virtually gone by the beginning of March. Dispersion of late stage zoeae into offshore waters was substantial in central and northern California and the pattern of dispersion appeared to be similar in both areas. By late April megalopae were found at high densities along the central California coast. Juvenile crab studies comparing 1977 with 1978 demonstrated that the l977 year-class was substarrtially more abundant (4 to 1) than 1978; they showed that the centers of crab concentration were located in the northern portions of the San Francisco Bay estuarine complex and moved farther up the estuary during the drought (1977); they found that sex ratios favored males in 1977 but were 1 to 1 in 1978; and growth rates were found to be greater for males than females after 1 year of age. A study on the staging of intermolt megalopae showed the sequence of stages to be a clear developmental process. The length of the stages was determined and the distribution of field-collected megalopae from 1977 plotted. Megalopae in San Francisco Bay, just outside the mouth of the Bay, and in Drakes Bay generally were the closest to molting to the first crab instar. A large number of megalopae collected west of Pt. Reyes were in earlier stages of development. Stomach content analysis from demersal fishes supported findings from the plankton samples that the 1979 year-class is relatively strong. (56pp. Farley, Timothy A. (ed))

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