Life in a fishbowl: Prospects for the endangered Devils Hole pupfish (Cyprinodon diabolis) in a changing climate

Abstract

The Devils Hole pupfish (Cyprinodon diabolis) is a federally listed endangered species living solely within the confines of Devils Hole, a geothermal pool ecosystem in the Mojave Desert of the American Southwest. This unique species has suffered a significant, yet unexplained, population decline in the past two decades, with a record low survey of 35 individuals in early 2013. The species survives on a highly variable seasonal input of nutrients and has evolved in a thermal regime lethal to other pupfish species. The short lifespan of the species (approximately 1 year) makes annual recruitment in Devils Hole critical to the persistence of the species, and elevated temperatures on the shallow shelf that comprises the optimal spawning habitat in the ecosystem can significantly reduce egg viability and increase larval mortality. Here we combine computational fluid dynamic modeling and ecological analysis to investigate the timing of thresholds in the seasonal cycles of food supply and temperature. Numerical results indicate a warming climate most impacts the heat loss from the water column, resulting in warming temperatures and reduced buoyancy-driven circulation. Observed climate change is shown to have already warmed the shallow shelf, and climate change by 2050 is shown to shorten the window of optimum conditions for recruitment by as much as 2 weeks. While there are many possible reasons for the precipitous decline of this species, the changing climate of the Mojave region is shown to produce thermal and nutrient conditions likely to reduce the success of annual recruitment of young C. diabolis in the future, leading to continued threats to the survival of this unique and enigmatic species.

Diabolical survival in Death Valley: recent pupfish colonization, gene flow and genetic assimilation in the smallest species range on earth

“…The population size typically decreases in response to reduced winter food availability and rebounds in the spring. Year-round water temperatures in Devils Hole remain near 328C [21]; however, broad thermal tolerances in Cyprinodon from 21.98C to 45.58C [25][26][27], such as Cyprinodon pachycephalus which completes its entire life cycle at 448C [28], suggest that diabolis should tolerate higher water temperatures (contra [29]). …”

Land Cover, Land Use, and Climate Change Impacts on Endemic Cichlid Habitats in Northern Tanzania

“…It lives in an underground cave with water from a single aquifer-fed thermal pool in the Desert National Wildlife Refuge Complex in Nye County, Nevada [106]. By 2013, the wild population was recorded to have decreased to less than 40 individuals [107]. It was among the first species to be listed on the U.S.…”

“…Despite this protection, populations of C. diabolis have declined since 1995; one of the potential causes being increased water temperatures caused by climate change, and therefore, decreased dissolved oxygen. Projected climate change by 2050 was found to compromise the recruitment window for juvenile fish, decrease egg viability and increase larval mortality [107].…”

Endocrine and metabolic impacts of warming aquatic habitats: differential responses between recently isolated populations of a eurythermal desert pupfish

“…Such temperature changes are likely to impact the region's native fishes given that many of these taxa occur only in a few small, isolated habitats and have limited ability to shift their geographical range (e.g. Hausner et al ., 2014). Assessing patterns of local population variation in thermal physiology will therefore be crucial for identifying populations most likely to persist under a changing climate (Chown et al ., 2010; Hoffman and Sgrò, 2011).…”

“…Even for species where these habitats are currently protected, a changing climate may lead to altered temperatures and nutrient cycling in patterns that impact the energetics, growth and reproduction of native desert fishes (e.g. Hausner et al ., 2014). For other desert fishes, habitat loss resulting from groundwater extraction or flow impediments, such as dams, has made it necessary to translocate fish to unoccupied habitats to establish additional populations or to breed fish in captivity for reintroduction into the wild (Johnson and Jensen, 1991; Minckley et al ., 1991).…”