Big Spring Spinedace

Lepidomeda mollispinis pratensis

Description

The Big Spring spinedace, Lepidomeda mollispinis pratensis, is a small, minnow-like fish, characterized by two weak, spiny rays in the dorsal fin. Bright silver in color, it ranges from 2-3 in (5-7.6 cm) in total length. This subspecies is one of seven taxa belonging to the Plagopterini, a unique tribe of fishes that is restricted to the lower Colorado River system.

Behavior

This species has been little studied and its behavior and breeding biology are largely undescribed. It is probably omnivorous.

Habitat

The Big Spring spinedace inhabits a clear, clean, shallow stream fed by perennial springs. When first discovered, it appeared restricted to a spring-fed marsh that has since dried up.

Distribution

The ancestors of this species became isolated in remote, spring-fed meadows of southern Nevada at the end of pluvial times, when the climate became warmer and drier. The region where the spinedace is found—Meadow Valley Wash—once contained Lake Carpenter and Carpenter River, which flowed into the Colorado River more than 10,000 years ago. The Big Spring spinedace was first discovered in a large marsh adjacent to Big Spring near the town of Panaca (Lincoln County), Nevada. Subsequently, diversion of water from the spring for irrigation caused the marsh to dry up, and the Big Spring dace was thought to be extinct. In 1978 personnel from the Nevada Department of Wildlife discovered a small population of the Big Spring spinedace in Condor Canyon, just northeast of Panaca. Condor Canyon comprises about 4 mi (6.5 km) of Meadow Valley Wash with perennially flowing water. In 1980 state biologists transplanted spinedace above a barrier falls to establish the fish in all portions of the available habitat, although by the time the 1994 Recovery Plan for the species was published, distribution was described as being limited to a 5 mi (8 km) section of Meadow Valley Wash, which flows through public and private lands. The fish is fairly abundant within this limited habitat of Condor Canyon, but actual population size has not been determined. The fish has been extirpated from the Panaca (Big) Spring outflow stream, due to habitat modification and non-native species introduction.

Threats

The Big Spring spinedace is threatened by its very limited distribution, which prevents any expansion of the population, by the danger of catastrophic destruction of this limited habitat, and by the introduction of non-native species. In some places the stream in Condor Canyon is only a few feet wide and could be disrupted by water diversion, use by livestock, or prolonged drought.

Conservation and Recovery

The Bureau of Land Management administers about 75% of the canyon and includes most of the land in a grazing allotment. The allotment has been inactive for some time, however, and is not expected to be renewed. The Nature Conservancy owns about 40 acres (16 hectares) of land at the upper end of Condor Canyon and has agreed to cooperate with the U.S. Fish and Wildlife Service (FWS) to recover this species.

On the basis of ongoing research, state and federal biologists will determine a suitable transplant location within the fish's historic range and attempt to establish a new population. In the meantime, every effort will be made to prevent accidental or purposeful introduction of the mosquitofish—a non-native pest found in many regional waters—into Condor Canyon. Based on previous experience, the mosquitofish could eliminate the spinedace population in short order. The 1994 U.S. Fish and Wildlife Service Recovery Plan for the Big Spring spinedace has as its goal delisting of the species by 2006. The fish may be proposed for delisting when a self-sustaining population exists in Meadow Valley Wash in Condor Canyon for at least five consecutive years and its habitat is secured from all known threats. Recovery efforts should include restoration of habitat between Condor Canyon and Panaca Spring to allow the Big Spring spinedace population to expand into its historic habitat. Additionally, one or more self-sustaining refugia populations should be established to prevent the extinction of the species should unforseen catastrophic events severely impact or eliminate the Condor Canyon population. The Recovery Plan recommends that the Condor Canyon habitat be secured by obtaining conservation agreements with private landowners and in-stream water flow rights. Populations should also be monitored and the habitat enhanced; and the public should be educated through an outreach program.

Contact

U.S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Complex
911 N.E. 11th Ave.
Portland, Oregon 97232-4181
(503) 231-6121 http://pacific.fws.gov/

References

Deacon, J. E., C. Hubbs, and B. Zahuranec. 1964."Some Effects of Introduced Fishes on the Native Fish of Southern Nevada." Copeia 1964: 384-388.

Hardy, T. 1980. "Interbasin Report to the Desert Fishes Council." Proceedings of the Desert Fishes Council 10: 5-21; 11: 68-70.

Miller, R. R., and C. Hubbs. 1960. "The Spiny-Rayed Cyprinid Fishes of the Colorado River System." Miscellaneous Publications of the Museum of Zoology, University of Michigan 115: 1-39.

U.S. Fish and Wildlife Service. 1994. "Big Spring Spinedace Recovery Plan." U.S. Fish and Wildlife Service, Portland.