COSEWIC Assessment and Update Status Report on the Margined Madtom (Noturus insignis) in Canada
- COSEWIC Assessment Summary
- COSEWIC Executive Summary
- Species Information
- Population Sizes and Trends
- Limiting Factors and Threats
- Special Significance of the Species
- Technical Summary
- Literature Cited
- Biographical Summary of Authors
- Experts Consulted
- Appendix 1 - Record of captures for Canadian margined madtom
Name, Classification and Taxonomy
The margined madtom, Noturus insignis (Richardson 1836), is a small ictalurid catfish (family Ictaluridae). Within the catfish family, the Noturus genus is characteristically small with an adnate or attached adipose fin. The official French name for the margined madtom is chat-fou liséré, although chat-fou livré is used in older literature. The margined madtom is rare in Canada and is restricted to a few streams, rivers and lakes in Ontario and Quebec.
Goodchild (1990) provided a description of Noturus insignis in the original status report and an identification key was developed by Coad (1986). This fish has a light cream coloured belly, a light brown to grey back and chin barbels. Its dorsal and caudal fins are light brown with black edges. Its adipose fin is attached along the length of the body and continuous with the square caudal fin (Figure 1). Adults are commonly 100 mm in total length. Margined madtom can be distinguished from the stonecat, Noturus flavus, since the margined madtom has black-edged median fins, a premaxillary tooth patch without backward extensions and saw teeth on the hind edge of the pectoral spines while the stonecat lacks black-edged median fins, has a premaxillary tooth patch with backward extensions and may or may not have saw teeth along the hind edge of the pectoral spines. The tadpole madtom, Noturus gyrinus, differs from the margined madtom and the stonecat by the presence of a rounded caudal fin and absence of saw teeth on the hind edge of the pectoral fins. Other Canadian species of madtom include the northern madtom, Noturus stigmosus and the brindled madtom, Noturus miurus. Both of these species can be distinguished from the margined madtom by the presence of dark blotches or saddle marks on the back and sides. Madtom catfishes are cryptic fishes that are not often captured and may be easily misidentified. It is possible that this may lead to an underestimation of the number of individuals captured.
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