Distribution and habitat selection of endemic fish and invertebrate species within a desert spring refuge
Authors: Darrick S. Weissenfluh, Gene R. Wilde, Cristi R. Baldino
Year: 2009 (xli)
Abstract
The Warm Springs Complex (WSC) is one of four management units within Ash Meadows National Wildlife Refuge (AMNWR). It contains five low-discharge warm spring systems with individual flows ranging from 0.000113 to 0.000198 cubic meters per second (cms) and spring-source water temperatures ranging from 28o to 34oC. School Springs refuge is one component of the WSC. This spring has undergone dramatic anthropogenic transformation since 1969, when the Bureau of Land Management (BLM) increased pool habitat in an effort to preserve the endemic, federally-listed (1970) Warm Springs pupfish, Cyprinodon nevadensis pectoralis. In 1983, four additional concrete ponds were constructed at School Springs to further increase water volume available to Warm Springs pupfish. During the summer of 2008, AMNWR completed rehabilitation of the School Springs refuge: the large concrete ponds were removed and a ‘naturalized’ channel consisting of pools, runs, and riffles was created. There were three primary goals of the restoration: (1) eradicate three aquatic invasive species; (2) improve suitable habitat for the endangered Warm Springs pupfish and three endemic invertebrates which only occupy springs in the WSC; and (3) test hypotheses concerning endemic fish and invertebrate habitat selection and distribution inherent in the design of the refuge. Preliminary monitoring results indicate: (1) most Warm Springs pupfish (>80%) occupy pool habitat, but they may be distributed throughout the system from spring orifice to wash despite extreme diel temperature fluctuations (~15oC) in parts of the stream and (2) endemic invertebrates are narrowly distributed and are restricted to specific habitats, with the exception of the Warm Springs naucorid, Ambrysus relictus, which has been observed utilizing the entire stream channel.