This study investigated the small aquatic ecosystems of Santa Ana National Wildlife Refuge, located in a predominantly agricultural area of the Lower Rio Grande Valley, Texas. Fishes and water quality data were collected for 13 months to determine the status of fish populations and the factors which influence their distributions on the refuge.
Sixteen fish species were collected during the study, however, more than 20 species are known to inhabit the Rio Grande in the vicinity of the refuge. Water source played a major role in influencing fish species richness in these aquatic ecosystems. Diverted river water offered the best source of fish species immigrants.
Gambusia affinis, Cyprinodon variegatus, Menidia beryllina and Poecilia latipinna maintained relatively high abundances throughout the study. Gambusia affinis was the most abundant species collected from the refuge while C. variegatus contributed the greatest biomass. Fish abundance patterns were closely related to changes in water temperature
