Foskett Speckled Dace
Foskett Speckled Dace
Rhinichthys osculus ssp.
|Listed||March 28, 1985|
|Description||Silvery dace with dark blotches.|
|Habitat||Freshwater springs and outflows.|
|Food||Detritus, fish eggs.|
|Reproduction||Spawns in June and July.|
|Threats||Limited distribution, habitat destruction, pollution.|
The silvery Foskett speckled dace ranges from 1.8-3.1 in (4.5-8 cm) in length. It has large eyes and is often marked with dark blotches on its rear half. The belly may turn orange or red during breeding season. Breeding behavior has not been observed but it is thought that the species spawns on hard substrates between late May and early June.
This dace, which lives to 3 years, appears to be non-territorial but collects in small schools and is rarely found singly. It is a bottom browser, feeding on insects, detritus, and other fishes' eggs. It spawns in June and July.
It is not know if this species is migratory but larvae and juvenile dace have been observed in the marsh 6-10 ft (1.8-3.1 m) away from the adult population, and so either the adults migrated to spawn or the larvae or juveniles migrated.
This species is restricted to a single spring system, comprised on Foskett Spring and Dace Spring, and the overflow rivulets with mud substrates. Most of the population occurs in the springhole, which is about 6 ft (1.8 m) in diameter and 6-12 in (15.2-30.5 cm) deep. The outflow rivulets are only a few inches (or centimeters) wide and deep. A few individuals have been observed in the cattle tracks where water seeps continuously. The spring brook eventually turns into a marsh and finally dries up before reaching the bed of Coleman Lake.
The area around the spring supports grasses and other aquatic vegetation, including cattails. Cover that the fishes utilize include overhanging grasses, grass roots, and algae. The water is clear, of fairly constant temperature, and with slow but significant currents.
The Foskett speckled dace is endemic to a small spring system in the Coleman Basin on the west side of Warner Valley (Lake County) in arid south-central Oregon.
Foskett speckled dace still occurs in portions of the Foskett Spring system. In 1982, an attempt was made to transplant the fish to other ponds in the region with indifferent success. When this species was federally listed in 1985, less than 1,500 individuals survived, and the number has not appreciably increased. In 1998, the population was estimated at 200 individuals in the source pool, 700 in the spring brook, and 27,000 in the shallow pool marsh.
This species is threatened by actual or potential modification of its springs habitat. Ground water levels in the area have been lowered by pumping to support irrigation agriculture and may eventually decrease the flow of the Foskett Spring, which is already considered minimal. Ditching or otherwise tampering with the pools and outflows would probably destroy the entire spring system. Trampling by livestock that come to drink at the spring is a particular problem.
The spring hole was excavated and damned at some point to form a small reservoir, and the dace population may have reached its peak when the reservoir was functional. The population seems to be restricted by the size of the habitat, and Foskett Spring itself will probably never support more than 2,000 individuals. The wetland on the edge of normally dry Coleman Lake may have formerly provided some habitat, but it is now either occupied by cattails or trampled by cattle.
Other threats include encroachment of vegetation (cattails and rushes), decreases in the level of dissolved oxygen, pumping of groundwater, channelization, decreased water levels and flow, and erosion and siltation.
Conservation and Recovery
The Foskett speckled dace has been transplanted to an excavated area at the spring source, Dace Spring, located just south of Foskett Spring. This artificial habitat is in a muddy, well-vegetated situation. Attempts to transplant the fish into other nearby protected springs will continue. Both springs that contain the dace are in a geothermal area, so it is probable that other suitable habitat is available.
The Bureau of Land Management owns Dace Spring and expects to acquire Foskett Spring through a land exchange with the private owner. This will permit fencing of the habitat, removal of cattle that trample the area, monitoring spring water, and modifying the habitat to create deeper water with moderate vegetative cover.
Regional Office of Endangered Species
U.S. Fish and Wildlife Service
Eastside Federal Complex
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
Telephone: (503) 231-6121
Bond. C. E. 1973. "Keys to Oregon Freshwater Fishes." Technical Bulletin 58. Oregon State University, Agricultural Experiment Station.
Bond, C. E. 1974. "Endangered Plants and Animals of Oregon; Fishes." Special Report 205. Oregon State University, Agricultural Experiment Station.
U.S. Fish and Wildlife Service. 1985. "Determination of Threatened Status for Hutton Tui Chub and Foskett Speckled Dace." Federal Register 50: 12302-12306.