Loading the dice for Devils Hole pupfish (Cyprinodon diabolis)

Authors: Kevin P. Wilson, Bailey Gaines, Jeffrey Goldstein

Year: 2012 (xliv)

Abstract

The population of the Devils Hole pupfish (Cyprinodon diabolis) continues to be below historical levels. The spring 2012 count was 63 with the majority of fish observed on the shallow shelf. This was the lowest count since the spring of 2008 (45 adults). From the spring of 2008 through the fall of 2011 the pupfish population seemed to have stabilized between 100-120 adults. In response to the unexpected decline in the spring of 2012, two status check counts were conducted in June revealing a population between 102 and 118 adults. A multi-agency decision was also made to discontinue Early-Life Stage (ELS, larvae) monitoring of the pupfish population and to target larvae pupfish with a timed feeding over the shallow shelf. Recent completion of an updated pupfish population model in collaboration with Iowa State University suggests that the population is most vulnerable at the egg and/or early larval life-history stage/s. Future experiments examining fecundity of hybrid (C. diabolis x C. mionectes) pupfish and survival of ELS hybrid pupfish will help strengthen this model. Recent research has focused on ecosystem energetics and microbial biofilm dynamics. For example, primary production estimates using dissolved oxygen readings between June 2008 and March 2010 ranged from 4-21 mg O2 L-1 d-1 with a significant decline over this time period, potentially due to a change in the microbial biofilm community. Ecosystem respiration ranged from 1.5-9.7 mg O2 L-1 d-1 and significantly increased over this same time period. Because microbial biofilms are important components of this unique ecosystem, shifts in their composition or activity may threaten ecosystem stability by reducing background O2 concentrations below the physiological limits of the endangered Devils Hole pupfish and the entire biotic community. Recent flood and earthquake disturbances will also be discussed.