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

Abstract

The salt-water intrusion into a lagoon system of the Sian Ka'an Biosphere Reserve was assessed during 1 year and related to the marine component of the larval fish assemblage. This system is environmentally complex because of the penetration of marine water, and the discharge of surface and subterranean water. Biological samples were collected during four field expeditions from October 1996 to August 1997. Surface circular tows with 500-μm-mesh conical plankton nets with a flowmeter were made during the day. Position, depth, temperature and salinity were recorded at each sampling station. All fish larvae were removed from the samples and identified to the lowest possible taxon. Ichthyoplankton abundance was normalized to 100 m3 of water. The distribution patterns of the carangiid Oligoplites saurus, the herring Opisthonema oglinum, the dragonet Diplogrammus pauciradiatus and members of the Tetraodontidae were related to the wind-driven circulation pattern of the lagoons obtained using a numerical model. The analysis of the distribution of ichthyoplankton showed that these species are good indicators of the spatial salinity variations controlled by the hydrodynamic characteristics of the system. The spatial use of these estuaries as a habitat for fish larvae is therefore strongly influenced by salinity distribution, itself modulated by annual variation of wind stress.