Larval fish assemblages in the Gulf of California and their relation to hydrographic variability were analyzed from zooplankton samples and CTD data obtained from three oceanographic cruises made during autumn 1997, and spring and summer 1998. Sea surface temperature images derived
from NOAA-AVHRR data for the same periods were used. The Bray-Curtis dissimilarity Index defined three groups of stations persisting from autumn to summer, but varying in area and species composition. The first group, located in the vicinity of Ángel de la Guarda and Tiburón
islands, was dominated by Engraulis mordax in autumn and spring and Opisthonema spp. in summer. This assemblage is linked to low sea surface temperature that resulted from the strong tidal mixing characteristic of this area. An oceanic group in the major part of the central gulf
was dominated by mesopelagic species as Benthosema panamense, Vinciguerria lucetia, and Triphoturus mexicanus. A neritic group, defined on the eastern continental shelf in summer, included a mesopelagic species (Benthosema panamense), demersal coastal species (e.g.,
Eucinostomus dowii, Diapterus peruvianus, Etropus crossotus, and Lythrypnus dalli), and epipelagic species (Auxis spp.). The spawning of most of them is restricted to the shelf when high sea surface temperatures were recorded. The El Niño 1997–1998
resulted in reduced abundance of coastal pelagic species such as Sardinops sagax and Scomber japonicus.
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