Oregon Chub

Oregonichthys crameri

Description

The Oregon chub, Oregonichthys crameri, is a small minnow measuring up to 1.4 in (3.5 cm). The scales on the lower body are brownish-yellow, while the upper scales are brown to white. The fins are almost clear and almost transparent. This species has also been classified as Hybopsis crameri.

Behavior

Males, which measure more than 1.4 in (3.5 cm) in standard length, defend territories in or near aquatic vegetation. The number of eggs produced per female ranges from 147 to 671. Spawning occurs from the end of April through early August when water temperatures range from 60.8°F to 82.4°F (16°C to 28°C). Adults feed primarily on copepods, cladocerans, and chironomid larvae.

Habitat

The Oregon chub was once distributed through sloughs and overflow ponds. Population sites typically feature low-or zero-velocity water flow, depositional substrates, and abundant aquatic, or overhanging riparian, vegetation.

Distribution

The Oregon chub was formerly distributed throughout the lower elevation backwaters of the Willamette River drainage. Populations of the chub are now restricted to the Middle Fork of the Willamette River near Dexter and Lookout Point Reservoirs in Lone County, Oregon. Small numbers of the chub have also been observed on the lower North Santiam River, which forms the boundary between Linn and Marion Counties and in Gray Creek within the Finley National Wildlife Refuge in Benton County. In 1992 an additional population was discovered in a tributary to Lake Creek in Linn County.

Threats

It is believed the Oregon chub has been adversely affected by changes in and elimination of its backwater habitats. The main stem of the Willamette River was formerly a braided channel with numerous secondary channels, meanders, oxbows, and overflow ponds that may have provided habitat for the chub. The construction of flood control projects and revetments, however, have altered historical flooding patterns and eliminated much of the river's braided channel pattern. The period of construction of flood control structures directly coincides with the period of decline of this species. Habitat loss has also resulted from siltation of shallow habitats from logging and construction activities, unauthorized fill activities, and changes in water level or flow conditions from construction, diversions, or natural desiccation. This species is also threatened by chemical spills and competition. Direct mortality is a potential threat from chemical spills from overturned trucks or oil tankers, runoff or accidental spills of brush control and agricultural chemicals, and overflow from chemical toilets in campgrounds. Competition for resources and predation may be a result of intentional or accidental introductions of non-indigenous fish species.

Conservation and Recovery

Conservation measures provided to species listed as endangered or threatened pursuant to the Endangered Species Act include recognition, recovery actions, requirements for federal protection, and prohibitions against certain practices. Recognition through listing encourages conservation measures by federal, international, and private agencies, groups, and individuals.

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
Telephone: (503) 231-6121
http://pacific.fws.gov/

Reference

U.S. Fish and Wildlife Service. 18 October 1993. "Determination of Endangered Status for the Oregon Chub." Federal Register 58 (199): 53800-53804.