Ongoing restoration projects for the endangered Moapa dace, Moapa coriacea, at the Moapa (Muddy) Warm Springs, Clark County, Nevada

Authors: David Syzdek, Michael Schwemm

Year: 2022

Abstract

The Moapa (Muddy) Warm Springs in Southern Nevada is a regional carbonate warm water spring complex that forms the headwaters of the Muddy (Moapa) River. These springs and associated streams are habitat for an endemic suite of thermophilic aquatic species that includes the federally endangered Moapa dace (Moapa coriacea). Currently, the Southern Nevada Water Authority (SNWA), US Fish and Wildlife Service (USFWS), Nevada Department of Wildlife (NDOW) and other stakeholders are undertaking recovery actions for the Moapa dace and its habitat. These include construction and removal of fish passage barriers, removal of invasive species and habitat restoration. To facilitate recovery of the Moapa dace and other native species, SNWA purchased the 1,218-acre Warm Springs Ranch in September 2007 and designated it the Warm Springs Natural Area for conservation and environmental stewardship purposes. In 2008, Moapa dace numbers suddenly declined to a record low of 459 individuals. Following this nadir, SNWA, NDOW and USFWS conducted stream restoration work and intensive habitat improvements to improve conditions for the Moapa dace. Since 2008, NDOW successfully treated the Upper Muddy River with rotenone to control the invasive and predatory blue tilapia (Oreochromis aureus). Furthermore, stream restoration and clearing of dense stands of invasive tamarisk (Tamarix spp.) and fan palms (Washingtonia filifera) are facilitating the re-establishment of native riparian vegetation, providing prevention of future wildfires and continued improvement in Moapa dace numbers. Moapa dace numbers are currently stable at a significantly higher level than in previous years but have yet to reach recovery levels of 6,000 fish. Recent snorkel counts recorded 1,956 Moapa dace in February 2022, and 2,221 Moapa dace in August 2022. Work continues to improve dace habitat, improve stream connectivity, and to monitor for invasive species. In 2015, a removable fish barrier was opened to allow Moapa dace access to its entire historical range. In 2018, a property purchase by SNWA on the North Fork acquired additional habitat which is currently being restored. In 2019 and 2020, 88 Moapa dace were translocated into the South Fork and those fish have successfully reproduced and now have a stable population. In 2021, 90 Moapa dace were transferred to the Lake Mead Fish Hatchery for a NDOW fish propagation program. Fish produced in the hatchery will be used to augment wild populations. In 2022, USFWS constructed a new stream channel to replace a culvert and waterfall blocking fish passage. Stakeholders are currently assisting Desert Research Institute with developing techniques to estimate Moapa dace populations and monitor for invasive aquatic species using environmental DNA techniques.