Research Document - 2012/174

Risk Assessment for Three Dreissenid Mussels (Dreissena polymorpha, Dreissena rostriformis bugensis, and Mytilopsis leucophaeata) in Canadian Freshwater Ecosystems

By T.W. Therriault, A.M. Weise, S.N. Higgins, Y. Guo, and J. Duhaime

Abstract

An ecological risk assessment for three dreissenid mussel species: the Zebra Mussel (Dreissena polymorpha); the Quagga Mussel (D. rostriformis bugensis); and the Dark Falsemussel (Mytilopsis leucopheata) was conducted for freshwater ecosystems in the western Canadian provinces, Ontario, and Quebec. This risk assessment considered probabilities of survival (habitat suitability) and arrival to 108 Canadian sub-drainages and the ecological impacts associated with these species. The ecological risk associated with both Zebra Mussel and Quagga Mussel invasions across the western provinces and watersheds directly adjacent to the Laurentian Great Lakes and St. Lawrence River was considered high. In contrast, the risk was considered low for most of eastern Ontario and Quebec where calcium concentrations were deemed too low to support large (invasive) populations. Due to the high salinity requirements of Dark Falsemussel, the ecological risk associated with this species was considered low for all Canadian freshwater ecosystems. However, the scope of this risk assessment did not consider coastal estuarine habitats where the ecological risk could be substantially higher. The largest ecological impacts associated with Zebra Mussel and Quagga Mussel were negative impacts on biota that inhabit the pelagic (offshore) zones of lakes or rivers (e.g., losses in productivity for phytoplankton, zooplankton, and planktivorous fishes), and to unionid mussels (severe declines in abundance and biodiversity).

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