Spatial and temporal variation of fish assemblage structure in a neotropical Mexican river

The introduction of non-native fish into the Teuchitlán River, in west-central Mexico, was suggested as a key factor behind change assemblage, and even extinction endemic species. characterization assemblage relationship between abundance anthropogenic conditions were evaluatedover 2-year period. Fish structure, species replacement, dominance examined along longitudinal environmental gradient. Physical chemical parameters water recorded. abiotic factors inferred from multivariate analysis. results showed that poecilid Pseudoxiphophorus bimaculatus dominant, biomass exceeded 50%in all sites seasons. Species diversity native greater upstream sites, which presented higher dissolved oxygen lower nitrates. ichthyofauna River has been replaced by This decline seems to be due not only interaction with but also multiple human impacts on lotic system.