Abstract
Previously known within Canada from the Flathead River, nominal Cottus confusus also occur in the Kettle, Columbia, and Slocan rivers of British Columbia. The latter populations are similar to those from Washington, and possess a post-maxillary pore, lower numbers of pectoral rays, prickles behind the pectoral fin, and a smooth head. They are sympatric with nominal Cottus bairdi, with some individuals morphologically intermediate between the two species. Flathead River samples of nominal C. confusus differ from Columbia River populations in absence of the pore and prickles, higher fin ray counts, and larger head papillae. Specimens of nominal C. bairdi previously reported from the St. Mary River (Saskatchewan and Nelson drainages) and Milk River (Missouri River drainage) of Alberta are similar to Flathead River C. confusus, with others intermediate between Flathead River C. confusus and Columbia River populations of C. bairdi and C. confusus. Differences between Flathead River and Columbia River samples suggest that these populations require separate status in Canada. Similkameen River samples of C. bairdi are morphologically variable, individuals from upstream populations having some characters similar to those of C. confusus. A thorough study of C. bairdi and C. confusus in the United States is needed to redefine species limits.
Published Version
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