Research Document - 2014/023

Information in support of a Recovery Potential Assessment of Threehorn Wartyback (Obliquaria reflexa) in Canada

By Lynn D. Bouvier, Jennifer A.M. Young and Todd J. Morris

Abstract

In May 2013, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assessed the status of Threehorn Wartyback (Obliquaria reflexa) and determined the designation to be Threatened. The reason provided for this designation is that, “This rare species historically occurred in the Great Lakes drainages including Lake St. Clair, western Lake Erie, and the Grand, Thames, and Detroit rivers. The species has not been found since 1992 in Lake St. Clair and the Detroit River and may be extirpated there due largely to the impacts of Zebra and Quagga mussels. It was last recorded from the Canadian side of Lake Erie in 1997. Pollution (sediment loading, nutrient loading, contaminants and toxic substances) related to both urban and agricultural activities represent a high and continuing threat at the three remaining riverine locations.” Threehorn Wartyback is currently not listed under the Species at Risk Act (SARA).

This Recovery Potential Assessment (RPA) provides information and scientific advice needed to fulfill various requirements of the SARA. The information may be used to inform the development of recovery documents and for assessing permits, agreements and related conditions, as per section 73, 74, 75, 77 and 78 of the SARA. The scientific information also serves as advice to the Minister of Fisheries and Oceans Canada (DFO) regarding the listing of the species under the SARA and is used when analyzing the socio-economic impacts of adding the species to the list as well as during subsequent consultations, where applicable.

This Research Document describes the current state of knowledge of the biology, ecology, distribution, population trends, and habitat requirements of Threehorn Wartyback. Threehorn Wartyback population sensitivity to perturbations, as well as the threats currently effecting known Threehorn Wartyback populations is discussed. Mitigation measures and alternative activities related to the identified threats, which can be used to protect the species, are also presented. This assessment considers the available scientific data with which to assess the recovery potential of Threehorn Wartyback in Canada.

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