The status of Moapa coriacea and Gila seminuda and status information on other fishes of the Muddy River, Clark County, Nevada

Moapa coriacea is endemic to the headwaters (Warm Springs area) of the Muddy River, Clark County, Nevada. The Warm Springs area was snorkeled and Moapa coriacea and Gila seminuda enumerated in August 1994 after a fire, and in May 1997 after a diversion dam had been removed from the downstream end. Gila seminuda had been reported in greatest abundance downstream from the Warm Springs area and we estimated the population there through mark and recapture from January to March 1995. There was a dramatic reduction in native fishes in the Warm Springs area between 1994 and 1997, coinciding with the invasion of Oreochromis aurea. Downstream from the Warm Springs area Gila seminuda was the most frequently netted species while O. aurea was relatively scarce. The fish population (native and non-native) decreased in a downstream direction; the causative factor(s) have not been identified.