Ichthyoplankton Composition in the Loop Current and Sargassum Habitats in the Northern Gulf of Mexico

Ichthyoplankton in the Gulf of Mexico (GOM) aggregate in two different habitats that serve to provide refuge and concentrate prey in an otherwise oligotrophic environment: the Loop Current (LC) a mesoscale oceanographic feature characterized by the transition of environmental conditions of the water mass between the GOM and Caribbean; and Sargassum, a two species assemblage of floating brown algae that is habitat for many larval and juvenile obligate and associated fishes. The objectives of this study were to characterize the density and community composition of ichthyoplankton within these habitats using multivariate analysis. I identified three unique assemblages of ichthyoplankton at the LCB: a transition assemblage found around the LCB and two peripheral groups originating from either GOM or Caribbean water masses. The LCB ecotone displays a unique biotic assemblage of economically important fishes and may be essential to the early life history of these fishes. Sargassum is considered a nursery because of its observed densities of larval and juvenile fishes and potential ability to act as a nursery. Sargassum is a spatially and temporally dynamic habitat driven by currents, winds, and storms. We identified two distinct ichthyoplankton assemblages that were associated by the type of collection gear. Sargassum morphology did not influence ichthyoplankton community structure because Sargassum is temporally unstable and unable to establish strong community structure. Community structure was influenced by temporal recruitment which is also evidence of an unstable environment and resulted in a correlation between spawning and recruitment of the ichthyoplankton to the Sargassum