Predacious Diving Beetle (Dytiscidae) Dynamics Within a Refuge Tank Ecosystem for the Endangered Devils Hole Pupfish (Cyprinodon diabolis).

Authors: Mitchell Stanton, Olin Feuerbacher, Jennifer Gumm, Corey Lee, Javier Linares-Casenave

Year: 2018

Abstract

The Ash Meadows Fish Conservation Facility (AMFCF) was established, in part, to maintain a captive population of Devils Hole Pupfish. Part of this effort included creation of a 100,000 gallon ecosystem simulation which was stocked with algae and invertebrates from Devils Hole, in addition to fish raised from eggs collected from Devils Hole. While the refuge tank has successfully maintained the fish population through multiple generations, efforts to recover eggs from the refuge tank have been largely unsuccessful. Predacious diving beetles (Dytiscidae) have been observed in the laboratory and in the refuge tank consuming both eggs and larvae. Beetle traps were designed and deployed in an attempt to reduce the numbers of beetles. Several treatments with varying substrate and baits were tested for effects on capture efficiency and retention. No treatments differed from controls, however, the traps proved effective in capturing substantial numbers of beetles. Two species of beetles were routinely captured in the traps, and these populations seemed to roughly segregate spatially within the tank. The apparent effects of beetle trapping on egg recovery success were immediate and dramatic. This work has allowed AMFCF to begin propagating additional fish derived from refuge tank eggs without being wholly reliant on wild-collected eggs.