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COSEWIC Assessment and Update Status Report on the Margined Madtom (Noturus insignis) in Canada



The habitat characteristics preferred by Noturus insignis were described by Goodchild (1990), McAllister and Coad (1974), and Taylor (1969). This fish prefers clear, high-gradient streams with moderate current among riffles with a boulder, rubble, or gravel substrate (Goodchild 1990). Similar habitat descriptions were provided for the margined madtom specimens captured in the riffle areas of the Fall River, Bolton Creek and the Mississippi River in Lanark County during 1997. The OMNR field collection sheets described the habitat in the Fall River as shallow with a maximum depth of capture of 0.6 m with slow to medium current. The substrate along the riffle area was composed of gravel with some sand and rubble with log debris. Both submergent and floating plants were present. In Bolton Creek, maximum depth of capture was 0.5 m with still to slow current and a gravel substrate with some rubble and boulders. No aquatic plants were present. In the Mississippi River, maximum depth of capture was 0.6 m, and the current was fast with a rubble, gravel and boulder substrate.

Increased beaver (Castor canadensis) activity potentially covers riffle areas and slows water flow eliminating riffle areas and margined madtom habitat (Coad 1986). Siltation caused by erosion, agricultural or urban development also affects the survival of the margined madtom; this fish is intolerant of silt covering the rocky substrate (Coad 1986). Goodchild (1990) and Coad (1986) reported that this fish is seldom found in areas with differing habitat conditions and any changes in suitable conditions may severely affect its survival. Since the publication of the original status report, Noturus insignis specimens were captured from lakes in Muskoka County, during 1993, indicating that the habitat preferences of this fish may not be as restrictive as once thought. In Lake Muskoka margined madtoms were captured in still water with a boulder and sand substrate. In Lake Joseph, specimens were captured in slow current with a boulder and rubble substrate with some gravel.