Variability of fish larvae assemblages relative to mesoscale features in the deep water region of the southern Gulf of Mexico

Abstract

In the Gulf of Mexico (GoM), mesoscale features strongly influence hydrographic and circulation patterns, which can favor larval retention and/or transport. Most ichthyoplankton studies in the southern GoM (south of 25°N) have focused on the continental shelves and the Bay of Campeche (BoC), and little is known about larval fish assemblages in the oceanic region. We compared the structure of the assemblages among stations from contrasting mesoscale features in the deep water region (depths greater than 1000 m), hypothesizing that there is a higher similarity in assemblages from stations within the same feature. Ichthyoplankton samples were collected in the upper 200 m during two oceanographic cruises. Analyses of sea surface heights and temperature anomaly profiles allowed us to identify the stations corresponding to specific mesoscale features, including cyclonic and anticyclonic eddies, upwelling, river discharge waters transported offshore, and the Loop Current. Larval fish assemblages were not strictly differentiated among features, except for one assemblage identified within an anticyclonic eddy. Stations within the BoC could be discriminated from the northern oceanic region due to high larval fish abundances and to the occurrence of taxa that inhabit coastal and neritic habitats as adults, which are transported offshore due to local oceanographic processes.