HISTORICAL COMPOSITION OF FISH ASSEMBLAGES IN THE ALVARADO LAGOON SYSTEM, GULF OF MEXICO.

The composition of fish assemblages in the Alvarado Lagoon System was updated with information collected between 1966 and 2008, divided into nine collection periods. A temporal analysis of the variation in species richness, species richness indices, rarity, and composition of ecological and trophic guilds was also carried out. A total of 113 species were recognized, 66 of which were present in most of the collection periods, forming a group with a constant presence in the lagoon system, in which marine and freshwater species predominated. This group showed the highest levels of similarity between collection periods; this was confirmed by the richness and rarity indices. Functionally, the composition of the ecological and trophic guilds did not show significant differences. The composition of the trophic guilds showed a prevalence of invertebrate consumers, macrocrustaceans, and small fish, supporting the fact that migratory marine species were the most numerous, with minor contributions from the other guilds. The contribution of marine or freshwater visitor species was not important in the characteristics of the assemblages. These results suggest that the environmental conditions of the Alvarado Lagoon System have remained without severe changes during the study period, thus allowing both the constancy of the fish community and that of the ecological and trophic guilds. [ABSTRACT FROM AUTHOR]