INFLUENCE OF HYDROGRAPHIC CONDITIONS AND WIND FORCING ON THE DISTRIBUTION AND ABUNDANCE OF DUNGENESS CRAB, CANCER-MAGISTER, LARVAE

The distribution of larval Dungeness crab (Cancer magister) was sampled by joint U.S.A./U.S.S.R. ichthyoplankton surveys off the coasts of Washington, Oregon, and northern California involving more than 120 stations from 5 to 360 km offshore and between 40 and 48-degrees-N latitude in each of the five years 1981-85. Observed cross-shelf distributions of megalopae were consistent with a mechanism by which diel vertical migratory behavior of the late-stage megalopae in the presence of wind-induced currents results in onshore transport to favorable settlement areas. Total onshore transport for 45 d prior to sampling, estimated as the effects of wind on a passive particle at the surface at night and ir. the Ekman layer during the day, was correlated with the nearshore megalopal abundance. Mean larval densities for each of the five cruises declined exponentially with time of year of the cruise. This implied (1) an instantaneous mortality rate of 0.066.d-1 and (2) that survival is independent of inter-annual variation in environment. Abundance of megalopae was not correlated with station hydrographic data (salinity, temperature, and dissolved oxygen) nor chlorophyll levels (satellite data from the Coastal Zone Color Scanner).