Ecological Structure of Estaurine Fish Communities: Habitat Linkages Among Dominant Species Groups in Terminos Lagoon, Mexico.

Terminos Lagoon in the southern Gulf of Mexico has 5 ecological subsystems: (1) fluvial lagoon systems (FLS) with permanent river discharge, low salinity, high turbidity and nutrients. (2) Central basin (CB) between marine and river conditions, intermediate salinity and variable transparency. (3) Inner littoral of Carmen Island (ILCI) with strong marine influence, high transparency and extensive seagrass meadows. (4) Carmen inlet (Estero Pargo, ESP) with a net outflow of water and high turbidity. (5) Puerto Real inlet (PR) with a net inflow of waters, high transparency and seagrasses. During a 15-month sampling, 13,691 individuals of 79 different species were collected in 264 trawls. Mandamango catfish, checkered puffer, silver perch, hardhead catfish and sea bream accounted for 63% of the total capture. Seventeen species accounted for 90% of all individuals, and 25 species had less than 5 individuals. Biomass and density peaked during the rainy and norte seasons at ESP, ILCI and FLS; and during the dry season at CB. Small individuals were captured in ESP and the FLS, and larger sizes in CB and ILCI, suggesting the role of the lagoon as nursery and feeding grounds. Salinity in ESP, and Secchi depth in the ILCI were the environmental controlling factors. In the FLS, the community ecology is controlled by numerous factors that limit the patterns of diversity and abundance. The dominant species were classified as: (1) resident species: (a) typically estuarine with reproduction in the lagoon and, (b) typically estuarine with spawning areas located in the inner shelf; (2) Seasonal species with a marked periodicity; and (3) Occasional visitors with limited spatial distribution. Fish usage for PR and at ESP showed 53% of common species for both areas, 30% exclusive to ESP and 15% to PR. Adults enter through PR in the fall, and spawn near-shore in the vicinity of the inlet. During the dry season, the density and biomass (juveniles and pre-adults) was highest in the ILCI and ESP areas coincidental to the highest primary production and the most rapid growth period of their life history