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National Aquatic Invasive Species (AIS) Risk Assessment for Zebra and Quagga Mussels, 2022 Update

National Peer Review Meeting – National Capital Region

April 4-7, 2022
Virtual Meeting

Co-chairs: Lisa Setterington and Justin Shead


In freshwater ecosystems, two prominent dreissenid mussel species, Zebra Mussel (Dreissena polymorpha) and Quagga Mussel (Dreissena rostriformis bugensis), both native to the Ponto-Caspian region, have a long history of invasion in both Europe and North America. In 2012, DFO Science conducted an ecological risk assessment for these two species for freshwater ecosystems with an emphasis on the western Canadian provinces, Ontario, and Quebec (DFO 2013 a, b; Therriault et al. 2013). The 2012 risk assessment contained some gaps that, if filled, would improve Aquatic Invasive Species (AIS) management decision-making as well as policy development. Identified gaps to be filled include,

  1. increasing the spatial coverage to include the Maritimes and Northern Canada,
  2. increasing the number and spatial resolution of environmental variables used, and
  3. applying updated georeferenced data on Zebra and Quagga Mussel distributions.

Since 2012, dreissenid mussels have continued to expand their distribution in Canada.  For example, Zebra Mussels were discovered in Lake Winnipeg in 2013 and subsequently spread across adjacent waterbodies. Similarly, in 2017, Zebra Mussels were first reported in Lake Memphremagog, Quebec, suggesting spread further eastward. Also, in early 2021, Zebra Mussel individuals were found in moss ball products associated with the aquarium trade across Canada increasing the potential for spread (DFO 2021).

Given this new information, a request to update the 2012 risk assessment was submitted by DFO’s Aquatic Invasive Species National Core Program. The updated risk assessment, which includes both the likelihood and consequences of an invasion, and subsequent science advice arising from this process will inform management actions, including early detection, response planning, and/or regulatory and policy measures aimed at mitigating potential risk posed by invasive Zebra and Quagga Mussel to Canadian freshwater ecosystems.


The specific objectives of this review process are to:

  1. Identify freshwater watersheds at higher risk of invasion by Zebra and Quagga Mussels in Canada by updating the 2012 detailed-level risk assessment including expanding the coverage of freshwater ecosystems across Canada and including newly available environmental and species distribution data.
  2. Identify data gaps and sources of uncertainty.

Expected Publications

Expected Participation



Participation to CSAS peer review meetings is by invitation only.

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