Diet and Trophic Structure of the Fish Community in a Small Sub-Tropical Lake in Central Mexico

Analyses of trophic structure and feeding habits of the fish community can provide information on the complex biotic and abiotic interactions in lake ecosystems. Based on stomach content and d(13)C and d(15)N stable isotope analyses, we conducted a comprehensive study of the diet of the fish community and its trophic structure in subtropical Lake Zacapu in central Mexico. Overall, there was good agreement between the results based on the diet and the isotope analysis. Fish diets consisted mainly of aquatic macroinvertebrates, which were abundant in the lake. Most species were secondary consumers and trophic generalists across the four sites and two seasons. The food web structure did not differ significantly between the sites or seasons. Our results suggest a low trophic position of native species having a wide spatial trophic niche and niche width. Trophic diet overlap was greater between native species (especially between species from the same family) than between non-native species. Our study provides new information on the trophic interactions in a subtropical lake, rich in endemic species and an important resource for human communities.