Characterization of fish assemblages in a tropical coastal lagoon in the northwest Gulf of Mexico

Tamiahua is one of the largest estuarine-lagoonal systems in the Mexican Gulf of Mexico. It has great economic and ecological importance due to high fisheries productivity and because it serves as a nursery, feeding and reproduction area for numerous populations of fishes and crustaceans. Spatial and temporal variations of fish diversity, abundance, dominant species and community inhabitants were determined based on samples taken on a bimonthly basis from May 1994 to March 1995. A total of 83 species, 62 genera and 32 families were collected, of which 14 species, 8 genera and 3 families were recorded for the first time in this area. Based on our collections and earlier reports, 136 species are known to use this lagoon system at some stage of their life cycle. The highest diversity and abundance values occurred during the rainy season (H'n = 2.7, D = 7.1, and F = 0.6; biomass = 59.3 g m(-2), density = 5.8 ind m(-2), and average weight = 10.2 g ind(-1)). Seasonal fluctuation of these parameters reflects the life cycles of different species (mainly the dominant species) related to the environmental dynamics of the ecosystem. Based on a graph-statistical analysis of the abundance and frequency data of 22,984 individuals, the fish species inhabiting the system were classified into four groups: resident, transient, irregular and rare. This analysis revealed the presence of 9 resident species, representing 77% and 73% of the total number of individuals and biomass, respectively. In order of importance, these species were Anchoa mitchilli, Membras vagrans, Hyporhamphus roberti, Bairdiella chrysoura, Eucinostomus melanopterus, Strongylura notata, Mugil cureina, Achirus lineatus, and Cynoscion nebulosus.