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We analyzed the relationship between the geostrophic flow pattern and the abundance gradients of the larval fish assemblages of the southern region of the California Current, in front of the Baja California Peninsula, Mxico, during two opposed environmental periods (summer and winter). During both seasons, the distribution patterns of the physical (sea surface temperature and mixed layer depth) and biological (Chlorophyll a and zooplankton biomass) variables were determined by the geostrophic flow. It established a northern region that belongs to the eddy found between the southern portion of California and 30 N, characterized by the presence of northern oceanic and coastal species with temperate and/or subarctic affinity. At the south of this gyre, during summer conditions (upwelling period), the main flow towards the south established an ocean-coast regionalization of the pelagic environment. The coastal assemblages were dominated by minor pelagic larvae (e.g. Sardinops sagax and Engraulis mordax) as well as some demersal species (e.g. Prionotus ruscarios and Scorpaena guttata), while the oceanic region was characterized by meso and bathypelagic species (Vinciguerria lucetia, Diogenichthys laternatus, Triphoturus mexicanus). During winter, the number of demersal species increased, and although the assemblages had ocean-coast segregation, the main gradient was latitudinal. This gradient was associated to the cyclonic and anticyclonic gyres from the oceanic area in front of the central region of the peninsula. The distribution given by the developmental stages (egg, preflexion, flexion and postflexion larvae) showed that apparently there was no dispersion of fish larvae outside the limits of the mesoscale structures observed. This suggests that the connectivity between areas was determined by this gyres which takes place mainly at the transition area in front of the central region of the Baja California Peninsula. This is an area with low abundance and species richness of fish larvae, where both the tropical-subtropical and temperate-subarctic faunas overlapped its distribution area.

Palabras clave: Fish larvae; Asemblages; Califoria Current.

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