Fish Response to Coupled Drought-Wildfire Disturbance: The Role of Thermal Guild

Global climate change is increasing the prevalence of wildfire and drought, with potentially severe consequences for riverine fishes.  However, most information concerning coupled drought-wildfire effects on fishes has come from cold-water systems, making it difficult to predict the responses of cool- or warm-water fishes to these climate-related disturbances.  The objectives of our research were to compare the responses of native and non-native cold-, cool-, and warm-water fishes to coupled drought-wildfire disturbance in the upper Gila River, NM, USA.  Fish biomass was measured in 2 sites each for fire-affected tributary, canyon, and valley habitats before and after consecutive wildfires.  To account for drought effects biomass was also measured in a tributary without wildfire.  Native warm-water and non-native cold-water fishes decreased in tributary habitats following single or repeated wildfires, with native warm-water fishes also decreasing in the canyon.  Native and non-native cool-water fishes also decreased, but decreases were related to drought.  Non-native warm-water fishes were unaffected by drought or wildfire.  These results suggested native fishes and non-natives with lower thermal tolerance are more susceptible to climate-related drought and wildfire compared to non-native warm-water fishes.  Management activities that ameliorate drought and wildfire effects my help conserve native fishes in a changing climate.