Species Fact Sheet Borax Lake chub Gila boraxobius
STATUS: ENDANGERED CRITICAL HABITAT: DESIGNATED
Borax Lake chub potentially occurs in these Oregon counties: Harney (Map may reflect historical as well as recent sightings)
The Borax Lake chub was emergency-listed as endangered in 1980, and a
final listing rule with critical habitat (47
was published in 1982. A recovery plan was published in 1987.
Status and Current Trends
The Borax Lake chub is endemic to Borax Lake and adjacent wetlands
in the Alvord Basin, Harney County, Oregon. Population estimates
of the chub in Borax Lake ranged from 10,625 to 34,634 during
1991 to 1997. Lower Borax Lake, which contained several thousand
chubs during wet years in the mid-1980s was dry from 1989 to 1991
and currently has no fish.
and Life History
The Borax Lake chub is a dwarf species of the genus Gila (a widespread
desert minnow). Adults are typically 33 to 50 millimeters (1.3
to 2 inches) standard length, with a maximum recorded size
of 93 millimeters (3.6 inches) standard length. The Borax Lake chub
has a large head which is concave in profile. The eyes are large,
and the lateral line is reduced. Pharyngeal teeth are uniserial
and well-hooked. Spawning can occur year-round, but primarily takes
place in the fall and spring (Williams &
Bond 1983, Scoppettone et al. 1995). Spawning occurs primarily
in gravel, rock outcrop, and sand habitats, which comprise only
16 percent of the substrate of Borax Lake (Perkins et al. 1996).
The Borax Lake chub is an opportunistic omnivore (Williams & Williams
1980, Scoppettone et al. 1995).
Borax Lake, with its highly variable thermal springs, comprises
one of the most unusual fish habitats in the United States. Borax
Lake is a natural lake fed from the waters of several thermal
springs, and is perched atop large sodium-borate deposits in the
Alvord Desert. It is small and shallow, about 4.1 hectares (10
acres) in size. Spring inputs near the bottom of a deep vent, 32 meters
(100 feet) below the surface, range from 40 to 148°C (104 to 300°F).
Surface water temperatures typically range from 16 to 38°C (61 to
but fluctuations occur and temperatures occasionally exceed 38°C
(100°F), causing fish kills as water temperature exceeds the
chub's critical thermal maximum (Scoppettone et al. 1995). Water
flows from Borax Lake into surrounding marshes, small pools,
and Lower Borax Lake.
Reasons for Decline
The thermal waters feeding Borax Lake face a long-term threat
from geothermal energy development. Proposals to drill wells near
the lake prompted an emergency listing of this species as endangered
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. The area
is currently fenced to exclude livestock.
Protection afforded by the 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, purchased a 65-hectare (160 acres) parcel of private
land including Borax Lake in 1993. An area of 260 hectares (640
ac) has been designated as critical habitat by the U.S. Fish and
Wildlife Service, which affords additional protection from actions
by federal agencies. The Steens Mountain Cooperative Management
and Protection Act of 2000 (Public Law 106-399) has withdrawn geothermal
and mineral development rights from the Borax Lake area. Additional
conservation actions needed include: 1) closure of the critical
habitat area to vehicle entry, 2) restoration of Lower Borax Lake
and adjacent marshes, and 3) monitoring of fish, invertebrate, and
Perkins, D.L., C. E. Mace, G.G. Scoppettone, & P.H. Rissler.
1996. Identification of spawning habitats used by endangered Borax
Lake chub (Gila boraxobius). United States Geological Survey,
Biological Resources Division, Reno Field Station.
Scoppettone, G.G., P.H. Rissler, B. Nielsen, & M. Grader.
1995. Life history and habitat use of Borax Lake chub (Gila boraxobius
Williams and Bond) with some information on the Borax Lake ecosystem.
National Biological Service. Northwest Biological Science Center,
Reno Field Station.
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.
Williams, J.E. 1995. Threatened fishes of the world: Gila boraxobius
Williams and Bond, 1980 (Cyprinidae). Environmental Biology of
Fishes 43: 294.