Influence of hydrographic conditions on larval fish assemblage structure in the northern Gulf of California

This paper analyzes the seasonal variability on larval fish assemblage structure and the relationships to hydrographic conditions during 4 seasonal surveys in the northern Gulf of California. Two periods were identified according to thermohaline properties and associated fauna: a cold period, when temperature drops and the coastal current flows equatorward in winter and spring (anticyclonic circulation), dominated by species of temperate and subtropical affinity (e.g., Engraulis mordax and Merluccius productus); and a warm period, characterized by poleward intrusion of Tropical Surface Water in summer and autumn (cyclonic circulation), with a high diversity of tropical-subtropical species (e.g., Benthosema panamense and Anchoa spp.). Cluster analysis defined 2 groups of stations and associated taxa: a Northern Group, located in the Delfín Basin, including mainly demersal taxa; and a Mainland-Insular group, of species with various affinities (demersal, coastal-pelagic, mesopelagic). Seasonal variability is identified as the main element in the structuring of larval fish assemblages. However, hydrodynamic changes influence the aggregation patterns and the prevalence of the coastal pelagic, demersal and mesopelagic biota throughout the year.