Population Prioritization for Conservation of Imperiled Warmwater Fishes of the Gila River Basin, Arizona, New Mexico, and Sonora

Continuing reductions in biodiversity, coupled with limited resources, have generated the need to perform triage to maximize success in conservation efforts.  The development and implementation of a species recovery program requires identifying which population units are most vulnerable to extirpation, which are most valuable to conserve, and which are most feasibly recovered.  Based on our review of the recent literature, there are few generalized approaches available to guide such population prioritization procedures.  We were able to adapt one existing method to rank populations of six imperiled, native, warmwater fish species of the Gila River basin of Arizona-New Mexico, USA and Sonora, Mexico.  The approach employs a series of binary questions to examine the biological consequences of extinction and whose scores accumulate to rank conservation value, and considers the CARE (comprehensiveness, adequacy, representativeness, efficiency) principles utilized in reserve-based systematic conservation planning efforts.  With significant adjustment, the method accommodated differences among species, evolutionary ecologies, habitats, and conservation problems between Pacific salmon stocks (the basis of the original method) and desert fishes of the arid American Southwest, and appears adaptable for application to other conservation situations and taxa.  Our analysis of the critically-endangered Gila basin fauna identified a new series of conservation values that should be considered when implementing recovery actions.  We believe a population ranking approach is essential and prerequisite to guide which population legacies will be included in or excluded from any broader geographically-based conservation program.   The method helps close the ‘research-implementation’ gap noted in the conservation planning literature by specifically indentifying necessary ‘in-the-water’ conservation actions for specific populations.  The next needed step to fully implement recovery planning for the imperiled Gila basin ichthyofauna is to identify and protect streams in which to replicate remnant populations.