Modeling the impacts of sub-seasonal environmental variability on the Devils Hole pupfish
AuthorNeuharth, Kayla D.
AdvisorHausner, Mark B.
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The endangered Devils Hole pupfish (Cyprinodon diabolis) occurs only in southern Nevada’s Devils Hole, a groundwater filled cavern 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 observable fish in 2013. Devils Hole pupfish (DHP) live 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. The pool where the DHP live receives a constant supply of 33.5°C water, near the edge of survivability for the DHP. On the ecologically critical shallow shelf, where DHP forage and spawn, high water temperatures can suppress successful recruitment. In this study, a computational fluid dynamic model of the shallow shelf was used to simulate springtime water temperatures for 2010-2015 and 2017. The model incorporates 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). Simulated water temperatures were then analyzed to examine relationships between water temperature and the success of seasonal recruitment of DHP. Water intermittently reaches above a 33.5°C threshold temperature and the length and frequency of the intermittent warm periods varies from year to year. Statistical analyses indicate an inverse relationship between consecutive warm days in a spring season and various metrics of DHP recruitment. Results from simulations will inform adaptive management strategies implemented by the National Park Service, U.S. Fish and Wildlife Services, and the Nevada Department of Wildlife to plan management and recovery actions that can mitigate the impact of high water temperature on DHP population.