Speckled Dace

Illustration of speckled dace, Rhinichthys osculus.

Species at Risk Act

SARA Status: TBD

Recovery Strategy: in preparation

COSEWIC Summary

Date of Assessment: April 2006

Common Name: speckled dace

Scientific Name: Rhinichthys osculus

COSEWIC Status: Endangered

Reason for Designation: The species is restricted to the Kettle River mainstem and two main tributaries in southcentral British Columbia where it appears to be limited by the availability of suitable habitat. As this population is isolated above Cascade Falls, it cannot be rescued from downstream United States populations. The Kettle River is a flow-sensitive system that appears to be experiencing increasing frequency of drought conditions. The species is threatened by these reduced water flows and projected increasing water demands.

Canadian Occurrence: British Columbia

COSEWIC Status History: Designated Special Concern in April 1980. Status re-examined and uplisted to Endangered in November 2002 and in April 2006. Last assessment based on an update status report.

Brief Description of Speckled Dace and Its Habitat

The speckled dace (Rhinichthys osculus) is a small stream-dwelling minnow, about 50 to 95 mm in length. It has a blunt nose that slightly overhangs the upper lip. There are barbels at the corner of the mouth in US populations, but not in the Canadian range. The caudal peduncle is moderately narrow, and the dorsal, anal and caudal fin lobes are rounded. Overall colouration is grey or grey-brown, with vague darker flecks above the lateral line. Mature males develop lateral spots similar to those in the Umatilla dace (Rhinichthys umatilla), but females and juveniles lack these markings. Speckled dace are most easily confused with lake chub (Couesius plumbeus).

The speckled dace is widely distributed in western North America, from the Columbia River drainage to the upper Colorado River in Arizona, New Mexico and Sonora Mexico. In Canada, the speckled dace is restricted to the Kettle and Granby Rivers in southern British Columbia. The majority of the Canadian population is isolated above Cascade Falls, which is a complete barrier to upstream migration. Distribution trends are not known, but the species’ current range in Canada is likely similar to its modern historic range. Throughout its broad distribution the speckled dace occurs as hundreds of divergent populations, many of which have been named as subspecies. The taxonomy is in disarray over much of its range, but a recent molecular analysis suggests eight major clades, one of which is centred in the Columbia River.

The speckled dace occurs in streams of all sizes, but is sometimes found in lakes. It is considered a generalist, and is usually found in water less than 1 m deep in pools or slow-moving river margins. In the spring during freshet, they may be found in deeper water in the Kettle River, behind large rocks, logs and other structures. Speckled dace are not strong swimmers and adults are usually found in areas with currents <0.25 m / sec.

Abundance trends in Canada are not known, and there have been no systematic censuses. Peden and Hughes (1984a) found the species widely distributed and abundant in the Kettle River from Carmi to Cascade, and in the Granby River. Juveniles were especially abundant relative to adults. Juveniles were widely distributed and abundant in many habitat types, whereas adults were patchy in distribution and associated with specific habitats with boulders and moderate current. Repeated surveys in 1978, 1979 and 1980 indicated abundance was stable. A more accurate estimate should be available in 2009 (M. Bradford, DFO, personal communication).

In the Kettle River, spawning begins in mid-July, on the descending limb of the freshet. The spawning season may be protracted, and females may be fractional spawners. Details of spawning in the wild have not been described in Canada, but are probably similar to accounts given for populations in Arizona and New Mexico. In both cases, spawning occurred over clean gravel in shallow (2.5 – 10 cm) water. John (1963) described some site preparation by males, which he referred to as a nest, but this behaviour was not observed in New Mexico by Mueller (1984). Both authors described spawning aggregations in which females were “swarmed” by males, depositing a few eggs each time she enters the spawning site. Fecundity is a function of female body size, and in the Kettle River varies from 450 to 2,000 eggs. In the lower Columbia, where female speckled dace can exceed 120 mm, fecundity can be in excess of 4,000 eggs.

Adult speckled dace feed mainly on aquatic invertebrates, but significant amounts of filamentous algae were also found in their stomachs. Juveniles and young-of-year have diets similar to adults, but with a higher proportion of periphyton and chironomids.

Given their restricted distribution, speckled dace can be considered vulnerable to a variety of threats. One of the primary factors in the vulnerability of speckled dace in Canada is their restricted distribution upstream of an impassable barrier at Cascade Falls. This barrier prevents natural movements into the upper Kettle River from below the falls, and would preclude natural recolonization in the case of a catastrophic event. A catastrophe would have to simultaneously affect the east and west fork of the Kettle River along with the Granby River to extirpate speckled dace above the falls, and is therefore unlikely. Careful management of habitat within the Canadian range is nevertheless required to secure the long-term persistence of speckled dace in Canada.

There has been no quantitative assessment of trends in habitat throughout the range of speckled dace, but historic and ongoing habitat impacts associated with settlement, forestry, agriculture, and industrial activities have likely had negative effects. Direct water use is extensive throughout the watershed, on tributaries and the mainstem, and many streams in the area are “fully recorded,” meaning that no additional water is available for allocating to consumptive uses. Consumptive uses of water are dominated by irrigation, which is seasonal, coinciding with periods of naturally reduced flow. The biological effects of these changes are likely negative, but are unquantified.

Some References

Baltz, D. M., P. B. Moyle, and N. J. Knight. 1982. Competitive interactions between benthic stream fishes, riffle sculpin, Cottus gulosus, and speckled dace, Rhinichthys osculus. Canadian Journal of Fisheries and Aquatic Science 39:1502- 1511.

Bradford, M. 2006. Impact of the proposed hydroelectric development at Cascade Falls on the conservation status of speckled dace (Rhinichthys osculus) in the Kettle River, British Columbia. Report for Fisheries and Oceans Canada.

COSEWIC. 2006. COSEWIC assessment and update status report on the speckled dace Rhinichthys osculus in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vi + 27 pp. (www.sararegistry.gc.ca/status/status_e.cfm).

Gilbert, C. H. and B. A. Evermann. 1894. A report upon investigations in the Columbia River basin, with descriptions of four new species of fish. Bulletin of the U.S. Fish Commission 14:169-207.

Haas, G. R. 1998. Indigenous fish species potentially at risk in BC, with recommendations and prioritizations for conservation, forestry/resource use, inventory and research. Fisheries Management Report 105. British Columbia Ministry of Fisheries, Victoria, BC.

Kaya, C. M. 1991. Laboratory spawning and rearing of speckled dace. The Progressive Fish-Culturist 53:259-260.

McPhail, J. D. 2007. The freshwater fishes of British Columbia. University of Alberta Press, Edmonton.

Mueller, G. A. 1984. Spawning by Rhinichthys osculus (Cyprinidae), in the San Francisco River, New Mexico. The Southwestern Naturalist 29:354-356.

Oakey, D. D., M. E. Douglas, and M. R. Douglas. 2004. Small fish in a large landscape: diversification of Rhinichthys osculus (Cyprinidae) in western North America. Copeia 2004:207-221.

Peden, A. 2002. COSEWIC assessment and update status report on the speckled dace Rhinichthys osculus in Canada, in COSEWIC assessment and update status report on the speckled dace Rhinichthys osculus in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. 1-36 pp.

Peden, A. E. and G. W. Hughes. 1984a. Status of the speckled dace, Rhinichthys osculus, in Canada. Canadian Field-Naturalist 98:98-103.

Peden, A. E. and G. W. Hughes. 1984b. Status of the speckled dace, Rhyinichthys osculus, in Canada. Canadian Field-Naturalist 98:98-103.

Rosenfeld, J. S. and T. Hatfield. 2006. Information needs for assessing critical habitat of freshwater fish. Canadian Journal of Fisheries and Aquatic Science 63:683–698.

Scott, W. B. and E. J. Crossman. 1973. Freshwater fishes of Canada. Bulletin of the Fisheries Research Board of Canada 184.

Wydoski, R. S. and R. R. Whitney. 2003. Inland fishes of Washington. Second edition. American Fisheries Society in association with University of Washington Press.

Recovery Team Documents

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