Margined madtom (Noturus insignis) COSEWIC assessment and status report 2012: chapter 8

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Limiting Factors and Threats

The margined madtom may be influenced by habitat change. Literature records (Coad 1986, Goodchild 1990) detail the specific habitat requirements of this species although recent captures in the lakes in Muskoka County suggest that this species may have a wider tolerance than first reported. Any activity that eliminates riffle areas or slows water flow may limit their population size (Coad 1986). This fish is intolerant of silt covering the rocky substrate (Coad 1986). Siltation is caused by erosion or agricultural and urban development. Low numbers of individuals, fluctuating population sizes and a limited amount of suitable habitat restrict the population size and distribution of the margined madtom, which is at the northern limit of its range in Canada. The collection of specimens may also have contributed to the depletion of populations already low in numbers.