MODELING THE IMPACTS OF SUB-SEASONAL ENVIRONMENTAL VARIABILITY AT DEVILS HOLE

The endangered Devils Hole pupfish (Cyprinodon diabolis) occurs only in southern Nevada’s Devils Hole, a water-filled fracture in a disjunct unit of Death Valley National Park. The species has experienced multiple declines in population in the past few decades, reaching a low of just 35 individuals in 2013. Devils Hole pupfish (DHP) live just 8-14 months and the population’s viability depends on seasonal annual recruitment, which primarily occurs in the springtime when food availability and water temperature are favorable for DHP. On the ecologically critical shallow shelf, where DHP forage and spawn, high water temperatures can suppress successful recruitment. In the late spring, peak daily water temperatures frequently rise above the ambient temperature of 33.5°C to temperatures lethal to DHP eggs. These peak water temperatures depend on both day-to-day meteorological conditions (which govern water-atmosphere energy transfer) and water level above the shelf (which controls heat capacity and water circulation patterns). Preliminary computational fluid dynamic simulations of the shallow shelf show the increasingly important influence of day-to-day meteorological variability as time progresses from early to late spring. The magnitude and duration and daily peak water temperatures are combined into a single representation of habitat quality. Results from these simulations will help the National Park Service, U.S. Fish and Wildlife Service, and the Nevada Department of Wildlife to understand the complex processes that affect DHP recruitment and to inform potential management and recovery actions that can mitigate these impacts.