COSEWIC Assessment and Update Status Report on the Copper Redhorse in Canada
- Assessment Summary
- Executive Summary
- COSEWIC History, Mandate, Membership and Definitions
- Lists of Figures and Tables
- Species Information
- Population Sizes and Trends
- Limiting Factors and Threats
- Special Significance of the Species
- Existing Protection or Other Status
- Technical Summary
- Acknowledgements and Information Sources
- Biographical Summary of Report Writer, Authorities Contacted, and Collections Examined
COSEWIC Status Report
The copper redhorse, (Moxostoma hubbsi, Legendre) (Figures 1 and 2) is one of seven species of the genus Moxostoma (family Catostomidae) that occur in Canada. Its discovery has been attributed to Vianney Legendre in 1942 (Legendre 1942), but it appears to have been first described by Pierre Fortin in 1866 as an already known Moxostoma (Branchaud and Jenkins 1999). Believing that it was a species previously described by Valenciennes, Legendre first named it Megapharynx valenciennesi, considering Megapharynx a new genus. More detailed studies later indicated that it was an entirely new species. On the basis of his description of 10 years earlier, Legendre (1952) officially designated the copper redhorse a new species and renamed it Moxostoma hubbsi in recognition of the famous ichthyologist Carl L. Hubbs. Robins and Rainey (1956) later placed it in the subgenus Megapharynx. However, the most recent study no longer recognizes Megapharynx as a valid taxon (Harris et al. 2002).
In 1998, the French common name of the species was changed from “suceur cuivré” (Tr.= copper sucker) to “chevalier cuivré” in order to facilitate the task of raising public awareness about the need to protect the species by eliminating any pejorative connotation associated with the word sucker (Branchaud et al. 1998). The French generic term “chevalier” (Tr.= knight) is now used to designate all species of the genus Moxostoma. This name refers to their large scales, which recall a knight’s armour. However, the second part of its common name has remained unchanged since it refers directly to the general coloration of the dorsal surface, head and sides, which ranges from a bright coppery sheen to olive. The ventral surface of the body is generally a paler shade of the colour of the sides or off-white and the fins are usually coppery to dusky (Scott and Crossman 1973).
Illustration by Paul Vecsei.
Illustration by Nathalie Vachon, from Vachon 2003a.
The copper redhorse is a large-scaled fish of the genus Moxostoma, a group of relatively large fish, with an inferior, protrusible mouth, lips with plicae and a pharyngeal apparatus with teeth arranged in an arch around the opening of the esophagus. It has 15 to 16 rows of scales around the caudal peduncle, like its congener the greater redhorse (Moxostoma valenciennesi), whereas there are usually 12 or 13 in the other species with which it occurs in sympatry in southern Quebec, namely the silver redhorse (M. anisurum), shorthead redhorse (M. macrolepidotum) and river redhorse (M. carinatum). Its short, massive head, shaped like an equilateral triangle, with a moderately high arch rising sharply behind the head, creating a humpback appearance, its pharyngeal apparatus, exceptionally robust with molariform teeth (18 to 21 per arch) (Figure 3) are the main characteristics by which it can be distinguished from the other species (Mongeau 1984, Mongeau et al. 1986, 1988, Scott and Crossman 1973).
Photograph by Yves Chagnon, Société de la faune et des parcs du Québec.
Gendron and Branchaud (1991) have described the morphometric, meristic and pigmentation characteristics of the larval (flexion mesolarvae) and juvenile stages, and Branchaud et al. (1996) have developed genetic analysis techniques for the identification of eggs and larvae. Several authors (Beauchard 1998, Vachon 2003b) have described the morphological features of the gill and pharyngeal arches in juveniles, and Grünbaum et al.(2003) have studied the sequence of ossification and chondrification of the caudal skeleton in larvae. Despite considerable efforts to develop other larval identification techniques, genetic analysis remains the most reliable method (Branchaud et al. 1996). At present, only larger juveniles (TL > 35 mm) can be identified by external criteria. In juvenile copper redhorse, the reduced number of pharyngeal teeth as well as their molariform appearance, widened base and more robust arches are already evident and can be used to distinguish them from the others. Dissection of the pharyngeal apparatus is still the technique of choice for confirming identification (Vachon 1999a, 2003a).
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