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The Purple Wartyback (Cyclonaias tuberculata) is a long-lived species of freshwater mussel currently found in three watersheds in Canada from lower Lake Huron through Lake St. Clair. The species was assessed by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) in May 2021 as Threatened, owing to a small number of extant locations and a continuing decline of habitat quality throughout its range. The species is considered extirpated from two historical locations. The Recovery Potential Assessment provides background information and scientific advice needed to fulfill various requirements of the Species at Risk Act (SARA). This research document provides the current state of knowledge on the species including its biology, distribution, population trends, habitat requirements, and threats. Purple Wartyback is a short-term brooder that is thought to use North American catfishes (Ictaluridae) as hosts for completing its life cycle. It is found in relatively deep, medium to large rivers with moderate to swift currents and occasionally lentic areas over sand, gravel, and cobble substrates. Long-term standardized sampling data suggest that at least two of the three populations in Canada may be growing; however, more years of data are required to span a full generation of this long-lived species. A threat assessment identified the greatest threats to Purple Wartyback in Canada as pollution from agricultural and urban sources, climate change (notably droughts), aquatic invasive species (including dreissenid mussels and Round Goby (Neogobius melanostomus)), and dredging. Limited information exists evaluating the impacts of these threats on Purple Wartyback specifically. Mitigation measures and alternative activities regarding habitat-related threats are presented. Important knowledge gaps remain surrounding the full extent of its distribution within known watersheds, habitat preferences by life stage, mussel-host interactions, and physiological tolerances to environmental conditions and pollutants. [ABSTRACT FROM AUTHOR]

The Lake Chubsucker (Erimyzon sucetta) is a small member of the Catostomidae family requiring clear, still, well-vegetated waters. In Canada, it is found in watersheds of southern Lake Huron through Lake Erie. The species was first assessed as Special Concern by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) in 1994, reassessed as Threatened in 2001, and was listed as Threatened under Schedule 1 of the Species at Risk Act (SARA) in June 2003. Lake Chubsucker was subsequently re-assessed by COSEWIC in 2008 (and again most recently in May 2021) as Endangered and is listed as Endangered under SARA owing to a decline in suitable habitat and extant locations, and multiple habitat-related threats. The Recovery Potential Assessment (RPA) provides background information and scientific advice needed to fulfill various requirements of SARA. This research document provides the current state of knowledge of the species including its biology, distribution, population trends, habitat requirements, and threats, with updated information from 2011 through 2020. Limited information exists to adequately assess the status of most populations, as records generally represent few individuals caught over a limited number of sampling events using varied sampling protocols. A threat assessment identified the greatest threats to Lake Chubsucker in Ontario as aquatic invasive species, natural system modifications, pollution, and climate change; however, the impacts of these threats are not well understood. Mitigation measures and alternative activities related to the identified threats are presented. Important knowledge gaps remain regarding population trends, physiological tolerances to environmental conditions and pollutants, and habitat requirements by life stage. [ABSTRACT FROM AUTHOR]

The Lake Whitefish (Coregonus clupeaformis) is a coldwater benthivore with a broad distribution and highly variable ecological and morphological traits across Canada. A species pair of Lake Whitefish in Lake Opeongo, consisting of a large-bodied and small-bodied form, was first discovered in 1940. Both forms (now considered separate Designatable Units, DUs) were assessed as Threatened by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) in April 2018. The reason for this designation was that both DUs are known only from Lake Opeongo, Algonquin Provincial Park, Ontario, and the introduction of aquatic invasive species could disrupt the unique ecological processes that drove divergence and maintains the species pair (COSEWIC 2018). The Recovery Potential Assessment provides background information and scientific advice needed to fulfill various requirements of the federal Species at Risk Act. This research document provides the current state of knowledge of the species pair including its biology, distribution, population trends, habitat requirements, and threats, which will be used to inform recovery plans. Limited information exists to adequately assess the status of either DU, particularly the small-bodied form. A threat assessment identified the greatest threats to the large- and small-bodied DUs of Lake Whitefish in Lake Opeongo as aquatic invasive species, climate change, and human disturbances; however, the impacts of these threats are not well understood. Mitigation measures and alternative activities related to the identified threats are presented, as appropriate. Important knowledge gaps remain regarding population trends, as well as differences in niche occupancy and impacts of current and anticipated threats on the two DUs. [ABSTRACT FROM AUTHOR]