Using physical thresholds to quantify anthropogenic impacts on the Devils Hole Pupfish

Authors: Mark B.* Hausner, Kevin P. Wilson, G. Gary Scoppettone, Francisco SuÁƒÂ¡rez, Scott W. Tyler

Year: 2015 (xlvii)

Abstract

The endangered Devils Hole pupfish, Cyprinodon diabolis, has been severely impacted by human development Á¢â‚¬ ’ both directly and indirectly Á¢â‚¬ ’ over the past six decades. Beginning in the late 1960s, local and regional groundwater pumping in the Ash Meadows area lowered the water level in Devils Hole, reducing both the area and volume of the optimal spawning habitat in the ecosystem. More recently, climate change has impacted the air and water temperatures in the Amargosa Valley, leading to changes in both allochthonous carbon inputs and reproductive success. In this study, we use a computational fluid dynamic (CFD) model to examine the physical effects of both climate change and local groundwater levels on Devils Hole and combine those results with a conceptual ecological model to consider the impacts of those changes on annual recruitment of C. diabolis. The CFD model predicts water temperatures as a response to climate and water level, and the ecological model is used to determine the timing of tipping points that may encourage or suppress the annual recruitment of C. diabolis. Using those data and historical counts of C. diabolis, we define seasonal thresholds for water temperature and food availability to quantify the annual optimal recruitment window. The combination of interdisciplinary modelling approaches offers a novel method to quantify and compare the suitability of habitat under a range of management and climate scenarios. Climate change to date is shown to have negatively affected the duration of optimal recruitment conditions, and climate change projections indicate that this impact will continue. However, the influence of water level on the duration of the annual optimal recruitment window is an order of magnitude greater than the influence of climate change Á¢â‚¬ ’ local and regional groundwater management will have a greater impact on the ecosystem than climate.