Threatened fishes of the world: Gila boraxobius Williams and Bond, 1980 (Cyprinidae).

From

Williams, J.E. 1995. Threatened fishes of the world: Gila boraxobius Williams and Bond, 1980 (Cyprinidae). Environmental Biology of Fishes 43: 294.

Conservation status

Vulnerable (IUCN red list), Endangered (U.S. Endangered Species Act).

Identification

A dwarf species of Gila, adults typically 33-50 mm SL (max. 93 mm SL), D 6-81 A 7-81 P 12-15, V 7-9f C 17-20. A large-headed chub with dorsal surface of head concave in profile. Eyes are large. Lateral line is obsolescent. Pharyngeal teeth are uniserial and well-hooked.

Distribution

Endemic to Borax Lake, Lower Borax Lake, and associated ponds and marshes in southeastern Oregon, U.S.A. (Williams & Bond 1980). All of these habitats comprise approximately 260 ha.

Abundance

The vast majority of chubs reside in Borax Lake. Seven population estimates of the chub in Borax Lake ranged from 3,934 to 13,319 during 1986-88 (unpublished data). Lower Borax Lake, which may contain several thousand chubs during wet years, was dry from 1989-91.

Habitat and ecology

Borax Lake is a 4.1 ha, shallow lake receiving water from several thermal springs. Inflowing water typically is 35-40°C, but fluctuations occasionally cause fish kills as water temperature exceeds fish's critical thermal maximum. Water outflows from Borax Lake into surrounding marsh, small pools, and Lower Borax Lake. The Borax Lake chub is an opportunistic omnivore (Williams & Williams 1980).

Reproduction

Spawning can occur year-around, but primarily in the spring (Williams & Bond 1983). Substantial spawning activity and larval chubs were observed (unpublished data) during autumn following cessation of unusually hot spring inflows during the preceding months.

Threats

The thermal waters feeding Borax Lake face a long-term threat from geothermal energy development. Proposals to drill wells near the lake prompted emergency listing of this species as endangered pursuant to the U.S. Endangered Species Act in 1980. Other threats include modification of the fragile lake shorelines, which easily diverts water away from the lake, and overgrazing by livestock. The fragile salt-crust shoreline of the lake also is easily damaged by off-road vehicle use.

Conservation action

Protection afforded by the U.S. Endangered Species Act has greatly curtailed exploratory drilling for geothermal energy development by creation of a zone of no surface disturbance around the most sensitive habitats. The Nature conservancy, a private conservation organization, has acquired a 10-year lease to the 65 ha parcel of private land including Borax Lake. The entire 260 ha area has been designated "critical habitat" by the U.S. federal government, which affords protection from actions of federal agencies.

Conservation recommendations

The recovery plan for the species (U.S. Fish and Wildlife Service 1987) provided the following excellent recommendations: 1) permanent protection by acquisition of private lands in the 260 ha habitat area, 2) closure of the "critical habitat" to vehicle, livestock, mining, and energy development activities, 3) restoration of Lower Borax Lake and adjacent marshes, and 4) monitoring of fish, invertebrate, and habitat characteristics.

Remarks

Borax Lake, including widely-fluctuating thermal springs, comprises one of most unusual fish habitats in U.S.A.

References

U.S. Fish and Wildlife Service. 1987. Recovery plan for the Borax Lake chub, Gila boraxobius. U.S. Fish and Wildlife Service, Portland, Oregon. 61 pp.

Williams, J. E. & C. E. Bond. 1980. Gila boraxobius, a new species of cyprinid fish from southeastern Oregon with a comparison to G. alvordensis Hubbs and Miller. Proceedings of the Biological Society of Washington. 93:291-298.

Williams, J. E. & C. E. Bond. 1983. Status and life history notes on the native fishes of the Alvord Basin, Oregon and Nevada. Great Basin Naturalist. 43:409-420.

Williams, J. E. & C.D. Williams. 1980. Feeding ecology of Gila boraxobius (Osteichthyes: Cyprinidae) endemic to a thermal lake in southeastern Oregon. Great Basin Naturalist. 40:101-114.

Preparator

Jack E. Williams, Division of Wildlife and Fisheries, Bureau of Land Management, Department of the Interior, Washington D.C. 20240 U.S.A.

Borax Lake chub habitat photos

Borax Lake chub images

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This page last modified:  09 December 2003