Research Document - 2013/028
Information in support of a recovery potential assessment of Mountain Sucker (Catostomus platyrhynchus), Milk River populations (Designatable Unit 2)
By D.A. Boguski and D.A. Watkinson
Abstract
In Canada, the Milk River system populations of Mountain Sucker (Catostomus platyrhynchus) are distributed in southwestern Saskatchewan and west in the Milk and North Milk rivers in southern Alberta. They appear to be disjunct from their conspecifics elsewhere in Canada. In November 2010, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assessed these populations of Mountain Sucker as a separate designatable unit (DU2) and assigned them a designation of Threatened. While there is no evidence to suggest that the Milk River populations have declined in abundance since the species was first identified there, COSEWIC considers this small, bottom-dwelling freshwater fish to be at risk due to its small area of occupancy and number of locations (eight). These conditions make Mountain Sucker particularly susceptible to habitat loss and degradation from altered flow regimes and drought that climate change is expected to exacerbate.
The Milk River populations of Mountain Sucker will be considered for legal listing under the Species at Risk Act (SARA). In advance of making a listing decision, Fisheries and Oceans Canada (DFO) has undertaken a Recovery Potential Assessment (RPA) that summarizes our current understanding of the distribution, abundance, and population trends of Mountain Sucker in DU2, along with recovery targets and times. Identification of threats to both the sucker and its habitat, and measures to mitigate these impacts, are also reported. This information may be used to inform the development of recovery documents, and to support decision-making with regards to the issuance of permits, agreements and related conditions under the SARA.
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