Distribution of Moapa dace and other fish in relation to wildfire at the Muddy River, southern Nevada

Authors: Lee H. Simons, Cailin C. Doyle, Laurie S. Simons

Year: 2010 (xlii)

Abstract

In July 2010, wildfire burned about 600 acres of the Warm Springs Natural Area adjacent to the Moapa Valley National Wildlife Refuge, 55 miles northeast of Las Vegas. Both the Refuge and Natural Area were established to protect the federally endangered Moapa dace (Moapa coriacea) and other thermophilic species endemic to the Muddy River and its warm springs emanating from the regional carbonate aquifer. Fire intensity was extreme in many areas due in particular to dense stands of exotic fan palm (Washingtonia filifera). Aquatic vegetation was burned or boiled in some shallow stream reaches. After the fire, charcoal was dense and mobile throughout the aquatic system. The day the fire was declared contained one shallow section of stream that previously supported Moapa dace, Moapa White River Springfish (Crenicthys baileyi moapae), shortfin molly (Poecilia mexicana), and mosquitofish (Gambusia affinis) was devoid of all fish. Within deeper sections of the streams, fish were generally distributed as they were before the fire. Ten days later all species except springfish had recolonized the shallow reach, but in reduced abundance. Six weeks after the fire, Moapa dace distributions were skewed strongly in favor of non-burned areas. The probable impact of water depth and fuel loading on fish survival during catastrophic wildfire will be discussed.