Abstract

Results of a study of the trophic ecology of 3,927 individuals from seven fish species (Eucinostomus gula, Lutjanus griseus, Sphoeroides testudineus, Cathorops melanopus, Achosargus rhomboidalis, Cichlasoma urophthalmus and Opsanus beta) which are dominant in a zone with submerged vegetation at Laguna de Términos are presented. The investigation was accomplished according to an intensive-sampling scheme that followed aspatial scale (bottoms with and without vegetation), and temporal scale (including day and night, and three climatic periods) with sampling throughout a year. Abundance (individuals m-z and g m-2) was estimated. Diet composition of each specie was determined by the analysis of 2,505 stomach contents. The index of relative importance (IRI) and the trophic niche range index were calculated. Affinities among each species diet, their distribution, and habitat preferences were analyzed using a similarity index, A. rhomboidalis and C. urophthalmus abundance was independent of temperature and salinity. E. gula, A. rhomboidalis, C. uropthalmus and O. beta occurs on bottoms with vegetation during day and night. L. griseus has preference for habitats with submerged vegetation and has nocturnal habits. C. melanopus was collected mainly on bottoms without vegetation during the night, and S. testudineus was found in the four sampling conditions. Cluster analysis showed relation in diets between C. melanopus and S. testudineus (0.78) and with C. urophthalmus (0.65). A. rhomboidalis and S. testudineus were related at 0.51, and L. griseus and O. beta diets were related at a low level. There were found ontogenetic changes in diet composition with a tendency to grater specificity. Seasonal variations in diets of all species were related to changes in weight and numerical proportions of the food items due to the stability of the studied area, which presented strong marine influence and high abundance, and diversity of benthic invertebrates, which provide the food basis for many local fish species at some point ÍD. their life cycles.

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