Background.

The Pom-Atasta system associated with the Terminos Lagoon has scientific, social, and economic importance. Numerous species depend on it to carry out their biological cycles.

Goals.

Analyze the ecological dynamics of the fish community in relation to the environmental variation of the system.

Methods.

From 2005 to 2014, 140 fish collections were carried out at 10 sites in the system, and physicochemical parameters were recorded. Principal Component Analysis (PCA) was performed to define environments. The sampling effort was validated using non-parametric estimators. Diversity indices and community abundance indicators were estimated. Non-Metric Multidimensional Scaling (NMDS) Analysis was performed to determine species-environment relationships.

Results.

The ACP determined three environments, one mesohaline, another oligohaline and one freshwater. A total of 59 fish species were identified. Non-parametric tests averaged 74 species for the system. The spatial variation of diversity (H’= 1.56 ± 0.33) and richness (D = 2.05 ± 0.48) was similar, with higher averages in the mesohaline environment. Evenness (J’ = 0.86 ± 0.09) was higher in the oligohaline and the low averages of H’ (0.64 ± 0.08), D (0.90 ± 0.76) and J’ (0.60 ± 0.46) in the freshwater. Temporally, the density (0.062 ind/m2) and biomass (3.15 g/m2) presented the highest averages during the north months and the highest average weight (123.68 g/ind) in the dry months. The NMDS indicated groupings of species related to the system’s environments and their ecological and biological strategies.

Conclusion.

Information on the fish community dynamics in the system related to the environmental variation of their habitats was integrated, which provides complementary knowledge to propose ecological criteria for the conservation of its biodiversity in the region.