Dungeness crab research program; Report for the year 1977

Program Staff, Harold G. Orcutt, Compiler (1977) Dungeness crab research program; Report for the year 1977. Menlo Park, CA, California Department of Fish and Game, Marine Resources Region, (Marine Resources Administrative Report, 77-21)

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Abstract

All 1977 year class larval stages, except fifth zoeae, occurred in the study area. California Cooperative Oceanic Fisheries Investigations (CalCOFI) plankton samples of February 1950, taken 67 and 111 miles off San Francisco, contained fifth stage zoeae and megalopae. Megalopae and early post-larval forms were found inshore and in the San Francisco-San Pablo Bay complex in the spring. The zoeae drifted offshore and later appeared inshore or were replaced by megalopae from without the study area. An invasion of warm water into the Gulf of the Farallones in late January and February may have accelerated development to the first crab stage, and zooplankters of oceanic and warm waters were found in association with crab zoeae. Eighty percent of a strong 1977 year class entered the Bay complex. Regression analyses were computer run comparing crab landings to quarterly oceanographic parameters coinciding with specific life history phenomena. Sea levels, indicators of ocean currents, are highly correlated to landings and also appear to be partly responsible for some high coefficient of determination values in multiple regressions. Crabs held at controlled temperatures revealed egg development, spawning, and feeding rates are affected by increased temperature. Crab mating success was 90% in the San Francisco area, and small samples from Eureka revealed similar success. Smaller ovaries in central California crabs prompt study of the possibility of lowered reproductive potential. Background levels of cadmium in juvenile crabs and water in which they were reared at the Marine Culture Laboratory were determined prior to beginning bioassays. Range-finding bioassays determined 10 mg/l of cadmium a mid-point for full-scale bioassays. Higher levels of petroleum hydrocarbons in the larger juvenile crabs from San Francisco Bay suggest crabs there acquire large hydrocarbon burdens. Satisfactory methods of rearing zoeal stages of crab were developed, and refinement of culture techniques was made for megalopae and post-larval instars. (59pp.)

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