RESISTANCE AND RESILIENCE OF SONORA SUCKERS (CATOSTOMUS INSIGNIS) TO EXTREME WILDFIRE DISTURBANCES IN THE GILA RIVER, NEW MEXICO

摘要

The increasing frequency of large, high-severity wildfires and resulting impacts on stream ecosystems necessitates the assessment of fish population resistance and resilience to these disturbances. Our objective was to quantify how density and growth of age-0, subadult, and adult Sonora suckers (Catostomus insignis) were influenced by two wildfires in 2011 and 2012 in the upper Gila River basin, New Mexico, that were followed by substantial ash flows and fish mortality. We predicted age-0 fish would experience greater mortality following wildfire than older fish, but compensatory dynamics, in response to decreased densities, would allow rapid recovery in the following years. Fish population data from an ongoing long-term study were available for the months of June and October (2008-2015) at five sites throughout the basin. We classified fish collections into three time periods: before, during, and after wildfires. As predicted, densities of age-0 fish sampled in October declined following wildfires, but contrary to our predictions, densities did not recover in the after-fire period. Adult densities remained stable during fire years, but were significantly lower in years after the wildfires. Delayed declines in adult fish were unexpected and we might attribute these declines to an interaction of wildfire and extreme monsoonal flooding in 2013. There was evidence of compensatory growth in subadults, as growth rates of passive integrated transponder-tagged fish 100-250 mm in total length were about twice as high after wildfires compared with prefire years. Overall, juvenile fish exhibited a lack of resistance and resilience to wildfire, thus recovery of this population will depend on recruitment of reproductive adults or emigration from nearby source populations.