Nevada Fish & Wildlife Office
Pacific Southwest Region

Moapa dace
(Moapa coriacea)

 
Class: Actinopterygii
Order: Cypriniformes
Family: Cyprinidae
Genus: Moapa
Species: coriacea
Length: up to 4.7 inches
Lifespan: 4+ years
Feed: omnivorous
Habitat: a variety of habitats in the Warm Springs area
 

Official Status:

Endangered
 

Life History:

Moapa dace apparently reproduce year-round, peaking in the spring. This species reproduces successfully in water temperatures ranging from 28 ° C-32 ° C. The species matures at 1 year of age. Very little is known about the reproductive characteristics of the Moapa dace. However, redds believed to belong to Moapa dace were found approximately 150 m downstream from a spring orifice in sandy-silt substrate at depths of 15-19 cm.

 

Distribution and Habitat:

  This species is endemic to Muddy (Moapa) River and associated thermal spring systems within the Warm Springs area of Clark County, Nevada. The Warm Springs area encompasses ten thermal spring provinces, which form the headwaters of the Muddy River. Moapa dace likely inhabited 25 springs and approximately 16 km of the upper Muddy River (Ono et al. 1983). Historically the Muddy River was 48.4 km long, however in 1935, with the completion of the Hoover Dam, Lake Mead flooded the lower 8 km of the river, rendering it unsuitable for Moapa dace. Recent investigations found adult Moapa dace occurring in low numbers in restricted portions of 3 springs and less than 2 miles of spring outflow and river in the Warm Springs area (USFWS 1983). The 1983 Moapa Dace Recovery Plan estimated the population at less than 1,000 individuals. However, a survey conducted between 1984 and 1987 estimated the population at 2,600 to 2,800 individuals (USFWS 1995).

Moapa dace occupy a variety of habitats in the Warm Springs area, including spring pools, tributaries (spring outflows), and the main stem Muddy River. Juveniles prefer tributaries and habitats with increasing flow velocities as they grow. Adults prefer both tributaries and the main stem Muddy River, with the largest adults occurring in the river.

The Moapa dace prefers habitat within local headwaters where water temperatures are between 28 ° C and -32 ° C and turbidity is low. It is known to occur in springs pools, spring feeders, small outflow streams, and the main river channel. A slight current exists in most areas inhabited by the species. Native waters for this unique fish are noted to be clear, with variable bottom types in pool habitats and may be spring deposited gravels or flocculent organic/silt. In outflow streams the bottoms may be of sand, gravel, pebbles and cobbles, or mud.

 

Threats:

  PAST THREATS:

This species significantly declined with the introduction of the shortfin molly (Poecilia mexicana) in 1963, and the extensive habitat modification that occurred 20 to 30 years ago. The greatest threat is physical destruction or alteration of habitat. Most or all of the springs originally containing Moapa dace still flow; however, the spring systems have been altered for recreation, irrigation, industrial, and municipal use.

Springs on the Frederick Apcar property have been channelized and piped by the Moapa Valley Water Company and diverted for domestic purposes. Muddy River water and water from the Warm Springs Ranch is diverted for agricultural, and industrial uses. The Moapa Dace Recovery Plan (1983) stated that this species was eliminated from all of the springs within the Desert Oasis Warm Springs Resort and the 7-12 Resort (now Moapa National Wildlife Refuge) prior to 1979 because the springs had been concreted and/or graveled, channelized, chlorinated, and had vegetation removed to create public swimming pools. However, NaturServe Explorer states that the streams on and immediately below the Moapa National Wildlife Refuge (est. in 1979) provide the only remaining spawning habitat (NatureServe Explorer 2001). Also that in June of 1994, a fire occurred at the Moapa National Wildlife Refuge and caused a population decline (NatureServe Explorer 2001).

CURRENT THREATS:

Past threats remain.

In addition to the introduction of the shortfin molly, other fishes including the common carp (Cyprinus carpio), channel catfish (Ictalurus punctatus), largemouth bass (Micropterus salmoides), fathead minnow (Pimephales promelas), and black bullhead (Ameiurus melas) have been introduced into the Moapa dace habitat and may affect the decline Moapa dace population in the future (USFWS 1995). Prior fish introduction have introduced fish parasites including tapeworms (Bothriocephalus acheilognathi), nematodes (Contracaecum spp.), and anchor worms (Lernaea spp.) which have adversely affected native fishes of the Muddy River (USFWS 1995).
 
 
 

Actions / Current Information:

 

  Date Title
  • 06/01/2013 Moapa Dace Numbers Based On Snorkel Surveys
  • 08/27/2009 Moapa Dace Spotlight Species Action Plan
  • 05/16/1996 Recovery Plan for the Rare Aquatic Species of the Muddy River Ecosystem (4MB PDF)
    Last updated: April 16, 2014