By GBI Research Associates Ambre Chaudoin and Robert Barlics

At a mere inch long, the Devils Hole pupfish (Cyprinodon diabolis) is the smallest of the desert pupfishes. This rare fish can be distinguished from other closely related species by its smaller and shallower body, larger head, lack of pelvic fins, and the deep-blue brilliance of the males—bluest of all the Cyprinodon pupfishes. It is often said that the Devils Hole pupfish has the smallest known distribution of any wild vertebrate, as it is endemic to a single spring— Devils Hole— located in a disjunct portion of Death Valley National Park within the Ash Meadows National Wildlife Refuge, Amargosa Valley, Nevada. Unlike the other flowing springs within Ash Meadows, Devils Hole is a still pool known as a fracture spring. It provides an opening to an extensive underground limestone cavern system of unknown depth. SCUBA divers have descended to 436 feet with no bottom in sight, dubbing Devils Hole as “a skylight into the aquifer.”

Between 3 million and 1 million years ago—during the late Pliocene era and into the early Pleistocene era—large, shallow inland seas and lakes connected valleys across the desert Southwest, including Death Valley and its neighbor to the east, Amargosa Valley. During the late Pleistocene, these water bodies began to dry up to form smaller, isolated lakes and rivers. Pupfish throughout the desert Southwest became increasingly isolated in these shrinking habitats, beginning their evolutionary divergence and speciation into the separate species and subspecies of Cyprinodont pupfishes we know today.

Today, only a few, small, isolated populations of pupfishes live in the remaining springs, streams, and rivers of the southwest. Perhaps the best known species is the Devils Hole pupfish.

Devils Hole, Amargosa Valley, Nevada. Devils Hole is located within a detached portion of the National Park Service–Death Valley, within the Ash Meadows National Wildlife Refuge.

On average, the crystal-clear water of Devils Hole is a balmy 92–93 degrees Fahrenheit. Combine this with low dissolved oxygen and limited food sources, and it is a wonder how any fish could survive in such an inhospitable environment. But survive they have, according to most experts, at numbers estimated in the several hundred for thousands of years. It is only fairly recently, after groundwater pumping and habitat alteration in the late 1960s and early 1970s, that the population has declined to unprecedented lows. It is now one of the most endangered species in North America.

Shallow shelf in Devils Hole, Nevada. The shallow shelf provides primary spawning and feeding habitat for the Devils Hole pupfish, and is critical for the continued survival of the species. It was the focus of a 1976 Supreme Court decision to retain a minimum water level above the shelf, ultimately shaping the Endangered Species Act of 1973 and water law across the nation. Photo courtesy U.S. Fish and Wildlife Service.

This is where the U.S. Fish and Wildlife Service (USFWS) and the Great Basin Institute enter the scene. The USFWS’s Ash Meadows Fish Conservation Facility (AMFCF) was completed in June, 2013. Its design combines a fish hatchery with an artificial ecosystem, or refuge, that simulates many of the extreme conditions in Devils Hole. The facility features a 100,000-gallon, 22-ft-deep tank—a replica of Devils Hole.

Part of our job duties as GBI Research Associate technicians is to monitor, record, and control water quality within the tank, including temperature, dissolved oxygen, pH, and flow rate, using specialized Supervisory Control and Data Acquisition (SCADA) software. We also monitor ambient air temperature and light by manually opening and closing louvers on the roof of refuge tank enclosure.

The mechanical room at the Ash Meadows Fish Conservation Facility. This room houses the majority of the plumbing and filtration system for the 100,000 gallon refuge tank that simulates Devils Hole topography and environmental conditions. Olin Feuerbacher (USFWS) in the background. Photo courtesy Ambre Chaudoin, Great Basin Institute.

The facility also has a propagation room that houses custom aquarium systems to breed fish, invertebrates, and algae. It also provides laboratory space for water chemistry and fish health and disease testing.

Current staff includes: Facility Manager/Fish Biologist, Corey Lee (USFWS); Aquaculturist/Fish Biologist, Olin Feuerbacher (USFWS); Propagation Support Technician, Ambre Chaudoin (Great Basin Institute); and Commissioning Support Technician, Robert Barlics (Great Basin Institute).

With cutting edge equipment and facility design, USFWS and GBI hope to achieve what has eluded those who worked on refuge attempts in the past—successful establishment of two captive, or “backup”, populations of Devils Hole pupfish, per the USFWS’s species’ Recovery Plan.

We are pursuing this goal by carefully collecting eggs from the wild population and hatching them at the AMFCF. Once hatchlings are sexually mature, we encourage them to spawn in aquaria before releasing them into the refuge tank. Part of the “encouragement” involves exposing the fish to factors believed to potentially induce mating activity, such as fluctuations in water temperature, dissolved oxygen, and lighting; and the introduction of spawning mats made of carpet and yarn (“shag” mats, as we like to call them). Despite the Devils Hole pupfish’s long-standing reputation as a fish that is difficult to breed in captivity, we have successfully bred a refuge population of 30 to 40 fish, and growing.

This shows the shallow shelf in the 100,000 gallon refuge tank at the Ash Meadows Fish Conservation Facility. The shallow shelf was carved out of a huge block of Styrofoam to mimic the exact topography of the shallow shelf in Devils Hole. It was encased in fiber-glass, carefully lowered into the refuge tank, and populated with algae, invertebrates, and other microscopic organisms collected from Devils Hole. Photo courtesy U.S. Fish and Wildlife Service.

The pupfish at top were collected as eggs from the wild population, hatched and reared in aquaria at AMFCF, and released as adults into the refuge tank. Photo courtesy Olin Feuerbacher, U.S. Fish and Wildlife Service.

At AMFCF, we also conduct research to guide management of the wild population of Devils Hole pupfish and aid in the conservation of other imperiled aquatic species. We’re hoping to provide insight into some of their unique adaptations, how they endured so long before human encroachment, and what measures might be critical for their conservation.

Surrounding Devils Hole is Ash Meadows National Wildlife Refuge, which is officially recognized as a wetland of international importance. It provides refuge to nearly 30 endemic species of plants and animals, containing the highest endemic biodiversity in the United States and second highest in North America. Encompassing 24,000 acres of seeps, springs, spring-fed wetlands, and alkaline desert uplands, it is the largest remaining oasis of its kind in the Mojave Desert.

Life in Devils Hole has the pupfish living at the very brink of its physiological tolerances. Because of this, even the slightest perturbation in its environment can cause drastic impacts to the population. The Devils Hole pupfish is thus often called a “canary in the coalmine.” This refers to its importance as a potential indicator of the health of our natural resources on a broader scale, particularly in the face of ongoing resource depletion, environmental degradation, and global climate change.

The species’ adaptations might also provide information useful to the fields of medicine, genetics, evolution, ecology, and biodiversity. For example, University of Las Vegas researchers recently discovered that hybrid Devils Hole-Ash Meadows Amargosa pupfish metabolize anaerobically for extended periods of time, possibly an evolutionary adaptation to the warm, oxygen-poor waters of Devils Hole. Anaerobic metabolism is a physiological process in which cells make energy from glucose in the absence of oxygen. The pupfish’s cells produce ethanol (ethyl alcohol) as a byproduct, resulting in liver changes similar to those seen in chronic alcoholism.

This phenomenon may also have implications for cancer research, as cancer cells also have this capability. If we allow species existing on the brink of survival such as the Devils Hole pupfish to go extinct, not only do we lose an irreplaceable piece of nature’s artwork, but we may also never fully realize their greater importance in our world.

Ambre Chaudoin (in water) : “My work as a GBI Research Associate helped me to further my career as a fish biologist and aquatic ecologist, as well as my knowledge of the many amazing species and ecosystems of the Mojave Desert. My past training and experience in aquatic invertebrate ecology and working with the Devils Hole pupfish has been directly applicable to my position at AMFCF. My experience working for GBI at Devils Hole has lead to my new position, Biological Sciences-Fisheries Technician with Death Valley National Park. I have additionally learned a great deal more about the Devils Hole pupfish and other fishes and aquatic systems of southern Nevada. My job has provided me with fantastic training and experience in designing and implementing a specialized long-term biological monitoring program, and also in developing methods for the culture and husbandry of a multitude of aquatic organisms, many of which have never before been cultured in the laboratory. I have also learned first-hand how agency driven conservation efforts function. It has been an honor to work with an incredible group of fisheries and conservation professionals and be a part of a very important, innovative effort.”

Robert Barlics (Commissioning Technician, Great Basin Institute): “My background is plumbing, electrical, and general carpentry, and I was unaware that fish live in the desert. Working in Ash Meadows National Wildlife Refuge has shown me there is a whole other world out there. I also gained an incredible amount of on-the-job knowledge about our refuge tank system’s interconnected nature and about working with such a large and complex partial recirculation aquaculture system. As an accomplished handyman, I can say that the plumbing system here would make the Death Star proud! As such, the commissioning process for this system was indeed challenging. It involved deciphering and sometimes rewriting complex blueprints and as-builts, troubleshooting equipment malfunctions, and some degree of system redesign and fine-tuning to adjust operations to meet our specifics needs. However, I am happy to say that our systems are now running smoothly, and the commissioning phase is wrapping up.”

Efforts of the Ash Meadows Fish Conservation Facility have been made possible by cooperative partnerships of the U.S. Fish and Wildlife Service, U.S. National Park Service–Death Valley, Nevada Department of Wildlife, and Great Basin Institute.