Environmental factors affecting structure and spatial patterns of larval fish assemblages in the southern Gulf of Mexico

The environmental factors that affect larval fish assemblages in the southern Gulf of Mexico were studied. Samples were collected with a Bongo net from the surface to a depth of 200 m, at 46 sampling stations, during spring 2006. The adult habitat was assigned to each larval fish taxon. Larval assemblages were defined by the Bray-Curtis index. A total of 182 taxa were found, of which most were oceanic, mid shelf and reef. Three assemblages were defined: Yucatan (YA), Tabasco-Campeche (TCA) and Oceanic (OA). The YA was located on the Campeche Bank, the wide Yucatan shelf where the most important hydrodynamic processes is a branch of Yucatan current. The TCA occupied the shelf of Tabasco and the southwestern shelf of Campeche, characterized by the continental freshwater discharge. The OA occupied the oceanic area of Campeche Bay, where the dominant hydrodynamic process is an almost permanent cyclonic gyre. As a result of the different hydrographic features, which are ocean currents, presence of gyres, freshwater discharge, and the topography; the Tabasco shelf, Campeche Bank (Yucatan shelf) and Campeche Bay constitute different regions. They are regions with clearly contrasting environmental scenarios. The geographic distribution of the 3 assemblages fitted well with these 3 hydrodynamically different areas. The structure and spatial distribution of the larval assemblages was determined first by the habitat of the adults and the spawning areas, and then being modulated by the hydrographic features that characterize each area.