Preparer

Gary L. Vinyard, Department of Biology, University of Nevada, Reno, Nevada, USA. 89557-0015

Conservation Status

Threatened (U.S. Fish and Wildlife Service, 1985, Federal Register 50:50304)

Identification

This small minnow (up to 75 mm TL) has very distinctive and conspicuous horny sheaths encasing both jaws. Head and body depth 3.0 to 3.5 times into body length. Lacking barbels, maxillary not reaching eye. Pharyngeal teeth in a single row, 5:4. Lateral line complete. Scales 15-18/68-78/10-13; 45-54 before the dorsal fin. Intestine long and coiled, peritoneum blackish-brown. (LaRivers 1962, Hubbs and Miller 1948).

Distribution

Desert dace are thermal endemics, and restricted to a series of less than 10 small springs and their associated outflows in Soldier Meadow, an area tributary to the Black Rock Desert, northwest Nevada, USA (41° 22' N, 119° 11' W). They have been isolated there for a long but indeterminate period. The springs are located at an elevation of approximately 1300 m which was apparently above the high stand of Lake Lahontan, a large Pleistocene lake which occupied the Black Rock Desert basin to the south (LaRivers 1962).

Abundance

Populations number several thousand individuals, though their numbers may fluctuate seasonally and have sometimes been adversely affected by agricultural water management (Nyquist 1963).

Habitat and Ecology

Desert dace are omnivorous and consume small invertebrates as well as scraping algae from the substrate. This scraping is presumably aided by the horny jaw sheaths. They are reported from some of the highest temperatures noted for cyprinids (>38°C, Hubbs and Miller 1948, Nyquist 1963), although highest population densities occur at somewhat lower temperatures (20-30°C). In cooler waters (<25°C), their distribution sometimes overlaps with another related native cyprinid, (Rhinichthys osculus), although the level of interaction is unknown.

Reproduction

Little is known of their reproduction, though it seems peak during the summer.

Threats

Primary threat to these fish is the potential impact of introduced predators or competitors. Goldfish (Carassius auratus) and largemouth bass (Micropterus salmoides) have been introduced into a reservoir which receives water from some of the springs containing desert dace. Historically, water diversion was identified as causing loss of some fish, although this problem has recently been reduced. An increasing threat to fish habitat in the area is from large numbers of campers and others who bathe in the thermal waters. The potential for geothermal exploitation of the source waters for the springs feeding Soldier Meadows appears limited at present, though this must also be regarded as a potential long-term threat.

Conservation Action

Most of the habitat of these fish is currently either under federal ownership or is protected by a conservation easement. Conservation plans are being planned to protect the fish as well as the other endemic species in the area.

Conservation Recommendations

For fish occupying such a small range, continued protection of the occupied habitats is essential. Although current recreational use levels do not seem greatly damaging, it may be necessary in the future to restrict access to some areas to prevent habitat disruption. An effort to educate local ranchers and recreational users should improve long-term prospects for the fish.

Remarks

Because desert dace comprise a monotypic genus, and are morphologically very distinctive, this suggests a long period of isolation. The area where these fish occur also contains at least one species of endemic snail and an endemic plant species. The area was important as a cultural resources for indigenous Indian tribes of the area and continues to be an important recreational area. These fish have been the subject to very little systematic investigation to date. Continued protection has been greatly enhanced by the recent acquisition of some of the springs by the Federal government, and by securing a conservation easement on much of the remaining habitat.

References

Hubbs, C.L and R.R. Miller. 1948. Two new, relict genera of cyprinid fishes from Nevada. Univ. Michigan. Mus. Zool. Occ. Pap. 507:1-30.

LaRivers, I. 1962. Fish and Fisheries of Nevada. Nevada State Fish and Game Commission. Carson City.

Nyquist, D. 1963. The ecology of Eremichthys acros, an endemic thermal species of cyprinid fish from northwestern Nevada. M.S. Thesis, University of Nevada. Reno.

This file is originally from the Biological Resources Research Center at the University of Nevada, Reno. For more information email gvinyard_at_unr.edu

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