Fish diversity in the Malpaso Reservoir in the Grijalva River basin of Mexico

Abstract

Abstract The Malpaso Dam creates the second largest reservoir in Mexico after the Belisario Dominguez Dam, both are located in the state of Chiapas in the Grijalva River basin. Despite the importance of the Malpaso Reservoir, fish diversity there has not been well documented. Fish diversity, abundance, and species composition were evaluated at four locations along the natural longitudinal zoning in the reservoir. We provide a checklist of fishes recorded in the Malpaso Reservoir based on a total of 22 survey events performed between March 2007 and June 2014. The fish fauna of the Malpaso Reservoir comprises 42 species, belonging to nine orders, 15 families and 32 genera, of which 39 species are native and three are invasive exotics. Cichlidae is the most diverse family, with 14 species (33.33%), followed by Poeciliidae with 11 (26.19% of total richness). Fish richness, abundance, and diversity are relatively homogeneous throughout the Malpaso Reservoir, showing no significant differences across the four sampling sites. Diversity values were low due to the strong dominance of five species, which together accounted for >70% of fish abundance. Canonical correspondence analysis (CCA) indicated that dissolved oxygen and temperature were the most important environmental parameters affecting associations of fishes in terms of their abundances. A cluster analysis (UPGMA) based on Morisita’s similarity index indicated that throughout the reservoir, the index values were close to 90 percent, indicating strong biological homogenization in the Malpaso Reservoir. This study found that dam construction in the Grijalva River basin has resulted in dramatic changes to multiple dimensions of the fish diversity, including a decrease in the total and native species richness, increasing biological homogenization, low values species diversity (H’) due to strong dominance of a few species, and the introduction of exotic invasive species.