SEASONAL-VARIATIONS IN SPECIES-DIVERSITY, ABUNDANCE, AND COMPOSITION OF FISH COMMUNITIES IN THE NORTHERN INDIAN-RIVER LAGOON, FLORIDA

We analyzed data from a long-term fisheries-independent monitoring pro gram to quantitatively assess seasonal variations in species diversity , abundance, and composition of fish communities in the northern India n River Lagoon. Between fall 1990 and 1993, over 2.24 million fish rep resenting 108 species and 43 families were collected by using seines, trawls, and gillnets during seasonal stratified-random sampling and mo nthly fixed-station sampling regimes. Seasonal collections were numeri cally dominated by less than 10 small estuarine forage species includi ng Anchoa mitchilli, Menidia spp., Floridichthys carpio, and Lucania p arva which were present in high abundances throughout the year. We obs erved strong seasonal patterns in abundance measures for several less common or transient species collected from shallow-water habitats (e.g ., Brevoortia spp., Trachinotus falcatus, Caranx hippos, Cynoscion neb ulosus, and Leiostomus xanthurus) and from lagoon-basin habitats (e.g. , Micropogonias undulatus and Diapterus auratus). Estimates of species richness and abundance were directly correlated with water temperatur e, reaching maxima during summer or fall and minima during winter. Spe cies diversity (H') ranged from 0.9-1.4 and followed similar seasonal trends. This study provides baseline estimates of seasonal variations in fish communities of the northern Indian River Lagoon, based on comp rehensive sampling techniques, that can be used for future comparisons of Indian River Lagoon fish communities.