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COSEWIC Assessment and Update Status Report on the Nooksack dace in Canada

Special Significance of the Species

The Nooksack dace is part of the Chehalis fauna, a group of fishes that diverged from Columbia fauna populations while isolated during the most recent glaciations in an ice-free refuge located south of Puget Sound and north of the Columbia River.  It and the Salish sucker, also listed as endangered by COSEWIC (and listed under SARA), are the only two members of this distinctive fauna to have dispersed, post-glacially, as far north as British Columbia (McPhail, 1997). Like most members of the Chehalis fauna the Nooksack dace is closely related to, but genetically and morphologically distinct from, the western North American (Columbia-Fraser) form of a continentally distributed species (longnose dace). Its distribution is also characteristic of Chehalis isolates, scattered populations in the Chehalis River and rivers draining the west side of the Olympic Peninsula and the east side of Puget Sound (McPhail 1997). As the geographic distribution of Chehalis isolates does not usually overlap with their closest relatives, determination of their taxonomic status is difficult. Their genetic, morphologic and distributional distinctiveness, however, indicates that they should be considered evolutionarily significant units for conservation purposes (cf. McPhail and Taylor, 1999). They are of some scientific interest in the study of evolutionary biology and biogeography (McPhail, 1967; Bisson and Reimer, 1977; McPhail, 1997).

Searches of the UBC library catalogue, and a number of zoological, First Nations, and anthropological data bases yielded no reports of Aboriginal use or traditional knowledge of R. cataractae or longnose dace.