Ichthyoplankton distribution as an indicator of hydrodynamic conditions of a lagoon system in the Mexican Caribbean

The salt-water intrusion into a lagoon system of the Sian Ka’anBiosphere Reserve was assessed during 1 year and related tothe marine component of the larval fish assemblage. This systemis environmentally complex because of the penetration of marinewater, and the discharge of surface and subterranean water.Biological samples were collected during four field expeditionsfrom October 1996 to August 1997. Surface circular tows with500-µm-mesh conical plankton nets with a flowmeter weremade during the day. Position, depth, temperature and salinitywere recorded at each sampling station. All fish larvae wereremoved from the samples and identified to the lowest possibletaxon. Ichthyoplankton abundance was normalized to 100 m³ ofwater. The distribution patterns of the carangiid Oligoplitessaurus, the herring Opisthonema oglinum, the dragonet Diplogrammuspauciradiatus and members of the Tetraodontidae were relatedto the wind-driven circulation pattern of the lagoons obtainedusing a numerical model. The analysis of the distribution ofichthyoplankton showed that these species are good indicatorsof the spatial salinity variations controlled by the hydrodynamiccharacteristics of the system. The spatial use of these estuariesas a habitat for fish larvae is therefore strongly influencedby salinity distribution, itself modulated by annual variationof wind stress.