A Novel Application of a Management Area Prioritization Method Supporting the Conservation of Freshwater Fishes

Protecting threatened native species within highly altered landscapes requires an array of management actions that address the diverse human threats to species of conservation concern.  In the American Southwest, freshwater fishes are some of the most critically imperiled fish faunas globally being highly vulnerable to human-induced environmental change such as increasing agricultural and domestic water demand, habitat loss and fragmentation, and invasive species.  This combination of threats that species experience in freshwater ecosystems poses a significant conservation challenge: how do we protect native fishes while still accommodating the widespread and diverse human uses of aquatic systems?  We present a novel application of a reserve selection algorithm in which two types of priority areas are identified to assist with native fish conservation efforts in the Gila River Basin of the American Southwest.  First, we selected for “conservation priority areas” that contained high native species richness and low non-native species richness representing areas with high conservation value associated with native fishes.  Second, we selected for “invasive priority areas” with high native species richness and high non-native species richness representing areas that could be the focus of management efforts aimed at reducing or controlling non-native species to benefit native fish persistence. We also integrated recently developed analytical methods incorporating river fragmentation and directional flow into the selection of priority areas. Conservation priority areas with the highest selection ranking focused broadly on the tributaries of the Verde River, headwaters of the upper Gila River, and some tributaries of the lower Gila River.  The invasive priority areas were focused on the lower Gila River mainstem, Verde River mainstem, and Salt River headwaters.  Our study highlights the utility of a systematic planning method to assist aquatic resource managers with strategic placement of existing conservation efforts promoting native fish species persistence in the American Southwest.