摘要：We studied the fish fauna of the Río Saín Alto (Río Aguanaval endorheic basin) in Zacatecas, Mexico, during
the dry (May) and wet (October) seasons of 2011 in order to evaluate changes in the distribution of the species and
its relationship with environmental variables. A total of 12 fish species (6 native and 6 exotic) were registered. The
longitudinal distribution of the species in the river during both seasons combined was 2 native species (Gila conspersa
and Catostomus nebuliferus) with ample distribution in the river (upper, middle and lower zones), 2 native species
(Campostoma ornatum and Notropis nazas) in 2 zones of the river (middle and lower), 4 species (2 native: Astyanax
mexicanus and Etheostoma pottsii, and 2 exotic: Cyprinus carpio and Oreochromis sp.) in the middle zone of the
river, and 4 exotic species (Gambusia affinis, Lepomis cyanellus, Lepomis macrochirus, and Micropterus salmoides)
with distribution confined to the lower zone of the river, especially in reservoirs. Species richness decreased with
altitude and after a flooding event. The factor analysis model determined that both altitude and flow velocity were
the factors that best explained the variation in the distribution of fish species during the rainy season, especially for
the exotic component.
