Geographical and Seasonal Patterns of Larval Fish Species Structure in the California Current Area, 1975

Analysis of I SO4 plankton tows from the 1975 CalCOFl cruise year yielded information on geographical and temporal patterns among 204 larval fish taxa. These taxa represented the spawn of fishes from a variety of habitats and water-mass affiliations. The larvae of certain commercially valuable pelagic spawning fishes (anchovy. hake. sardine. jack mackerel, and Pacific mackerel) dominated (75.5% of total larvae); these species are treated separately from the less abundant taxa (further separated into continental shelf. oceanic, and mesopelagic categories and taxa) to permit description of underlying hydrographically related distribution patterns within the California Current area. The composition and species abundance rcllations of the ichthyoplankton were similar to those reported from 1955-58. Exceptions were decreased relative abundance of sardine and increased proportions of anchovy larvae in 1975 vs 1955-58. Anchovy. hake. and jack mackerel larvae were moat abundant south of Point Conception. Abundances of rockfishes and bathylagids decrcascd. while those of flatfishes, myctophids, and gonostomatids increased. from north to south and inshore to offshore. Absolute ichthyoplankton abundance varied by a factor of IO between January-March (maximum) and September-December (minimum). Anchovy, hake. jack mackerel, rockfishes, sciaenids. myctophids. and bathylasids had January-March abundance peaks: niyctophids and gonostomatids had July abundance peaks: flatfishes were most abundant from OctoberDecember. Regional ichthyoplankton abundance tluctuations and compositions were related to hydrographic regimes. The area off northern Baja California marked a transition between predominantly cold-water or subarctictransition zone species with January-March abundance peaks and predominantly eastern tropical Pacific or warm-water species with summer and fall abundance peaks. This transition zone coincidcs with a persistent lobe of negative wind stress curl (surface-layer convergence) extending to the coast from offshore waters: