Hutton Spring Tui Chub

Gila bicolor ssp.

Description

The silvery sided Hutton tui chub ranges from 4.7-6 in (12-15 cm) in length. It has a dusky olive back and white belly. Its head is longer, the dorsal fin smaller, and the eyes larger than closely related chubs. Tui chubs in general have only one row of teeth on the pharyngeal bone, and the teeth of this tui chub are exceptionally robust. The Hutton Spring tui chub has been proposed for classification as Gila bicolor oregonensis.

Behavior

The omnivorous Hutton tui chub feeds on a wide range of snails, terrestrial and aquatic insects, amphipods, and perhaps algae. It prefers deeper pools and spawns in shallower water over beds of aquatic vegetation. Females deposit eggs between April and June, which hatch after about nine days.

Habitat

The Hutton tui chub is confined to two freshwater springs and associated outflow streams. It requires clean water of constant temperature. Hutton Spring was widened and diked in the 1970s to create a pool about 40 ft (12 m) wide and 15 ft (5 m) deep. Dredging removed most aquatic vegetation, except for a dense stand of rushes in the center of the pool. The Hutton Spring tui chub is currently the only fish inhabiting the spring.

Distribution

Populations of the Hutton Spring tui chub have been found in two spring pools and related outflow streams and marshes in Lake County, Oregon. The springs are situated at the northwestern edge of the dry Alkali Lake.

The Hutton Spring tui chub is known only from Hutton Spring and Three Eighths Spring—a smaller spring located slightly southeast of Hutton Spring. The chub population in Hutton Spring is thought to number about 300 individuals, and Three Eighths Spring supports an additional 150 chubs.

Threats

Surviving populations of the Hutton Spring tui chub are threatened by groundwater pumping for irrigation, which has caused spring discharges and water levels in the region to fall. The property owner has generally been protective of Hutton Spring and has fenced the area to exclude livestock. Three Eighths Spring remains unfenced and has been slightly disturbed by cattle. Both springs are vulnerable to habitat modification, either by dredging or diversion of water into artificial channels. Although it has not yet occurred, the introduction of non-native fishes into the springs would have a disastrous effect on the Hutton tui chub because of the narrow confines of the pools.

A nearby dump is a repository for an estimated 25,000 55-gal (208.2 l) drums of highly toxic chemicals. Residues from these improperly disposed wastes have leached into the surface and ground-water of the Alkali Lake area. It is possible that the springs inhabited by the Hutton Spring tui chub will become contaminated within the foreseeable future if the corroded storage drums continue to leak.

Conservation and Recovery

The Bureau of Land Management, the Environmental Protection Agency, and the Oregon Department of Environmental Quality are working with the property owner to further protect the habitat and spring area, and these agencies are examining ways to reclaim the toxic waste disposal site. One problem is to prevent siltation, erosion, water draw-down and vegetation destruction of the habitat caused by the property owner's spring back-hoe work for water control. And although the property owner has fenced the immediate vicinity of the spring, vegetative damage caused by cattle trampling has generally caused erosion and sedimentation in the area.

Groundwater contamination, the greatest threat to the spring, was caused by toxic herbicide material that was improperly disposed of about 1.75 mi (2.8 km) from the spring, and state and federal agencies are using their authority to require cleanup of the dump site. The use of heavy equipment at the dump site also caused modification of the spring area.

Contact

Regional Office of Endangered Species
U.S. Fish and Wildlife Service
Eastside Federal Complex
911 N.E. 11th Ave.
Portland, Oregon 97232
http://pacific.fws.gov/

References

Bills, F. 1977. "Taxonomic Status of Isolated Populations of Tui Chub Referred to as Gila bicolor oregonensis [Snyder]." M.A. Thesis. Oregon State University, Corvallis, Oregon.

Bond. C. E. 1973. "Keys to Oregon Freshwater Fishes." Technical Bulletin No. 58. Agricultural Experiment Station, Oregon State University.

Bond, C. E. 1974. "Endangered Plants and Animals of Oregon; Fishes." Special Report No. 205. Agricultural Experiment Station, Oregon State University.

U.S. Fish and Wildlife Service. 1985. "Determination of Threatened Status for Hutton Tui Chub and Foskett Speckled Dace." Federal Register 50:12302-12306.