Construction of A Mesocosm Re-Creation of Devils Hole

Simulation of a fish’s natural habitat in a laboratory setting can be a critical part of spawning success and important in maintaining fish health. By replicating natural environment as closely as possible, researchers may observe fish behavior in as realistic a simulation as is practical, and habitat variables may be tinkered with in ways not possible outside of the laboratory. Such reproductions are often highly automated, requiring complex and costly control equipment to operate. We describe the construction of a 4000-gallon mesocosm re-creation of Devils Hole, Nevada, that is driven primarily by biological processes and which allows for simplified control systems. This mesocosm houses hybrid Devils Hole pupfish, Cyprinodon diabolis x C. nevadensis mionectes. We discuss the abilities of an anaerobic denitrifying filter to both remove nitrate and provide calcium and trace element replenishment.  The chemical and biological processes in this novel filtration apparatus show distinct regions of activity and provide for an adaptable and scalable tool for controlling water quality.  We also discuss the combined use of a solar collection tube and a reverse daylight photosynthesis refugium sump to provide control of dissolved oxygen and pH. The sump also provides habitat for invertebrate and algal communities, which in turn become food items for the fish in the primary tank. The growth and progression of algal species generally followed the spring to summer transition seen in Devils Hole. Invertebrate communities do not yet resemble the ratios seen in Devils Hole, but are still in a state of heavy fluctuation.