Cooperative Fish and Wildlife Research Units Program: Arizona
Education, Research and Technical Assistance for Managing Our Natural Resources

Captive propagation of desert pool and spring fishes, whether for conservation or research purposes, faces obstacles in construction of appropriate habitats given the unique and often challenging environments these fish utilize in the wild. High temperatures, low dissolved oxygen, minimal water flow, and highly variable lighting are some of the conditions a researcher might be tasked with recreating when attempting to maintain these fishes in conditions resembling their natural environments. One such habitat is Devils Hole, Death Valley National Park, Nevada/California, USA, home of the critically endangered Devils Hole pupfish, Cyprinodon diabolis. Devils Hole is a considerably challenging environment to recreate. It is an underground spring system of unknown depth, with low (2.0 ppm) dissolved oxygen, and high water temperatures (33- 34°C). Lighting on the surface of Devils Hole is of short duration, usually at most 4 hours a day of direct sunlight, and almost all pupfish activity occurs on a small shallow shelf about 0.5 m below the water’s surface. Here we describe a mesocosm-scale habitat recreated to maintain hybrid Devils Hole x Amargosa pupfish (C. diabolis x C nevadensis mionectes) under conditions similar to those found in Devils Hole. This 13,000- L system utilized flow control and natural processes to maintain these conditions rather than utilizing complex and expensive automation. We designed a rotating solar collector to provide natural sunlight in a controlled manner, a biological reactor to consume oxygen while buffering water quality, and a reverse- daylight photosynthesis sump system to stabilize nighttime pH and swings in dissolved oxygen levels. This system successfully controlled many of the parameters desired; was used to help inform development of a larger desert fish conservation facility at Ash Meadows National Wildlife Refuge; and due to its scalable and modular design lends itself to adaptation for husbandry of other aquatic species from unique habitats at a reasonable cost. This information was provided in a report to the USFWS, in a thesis, and was published June, 2016 in the North American Journal of Aquaculture.