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Evaluation of Methods for Identification of Early Detection Monitoring Sites for Invasive European Green Crab in the Salish Sea, British Columbia

Regional Peer Review – Pacific Region

January 31 - February 2, 2022
Virtual meeting

Chairperson: Sophie Foster


The European Green Crab (EGC) is a high risk invader that is listed as a Control Species under the Aquatic Invasive Species (AIS) Regulations in the Fisheries Act. EGC can devastate aquatic ecosystems, displacing native species, degrading and disturbing native habitats (including eelgrass), and altering food webs. Thus, early detection is essential to inform AIS management. However, where to focus limited monitoring resources is an ongoing problem, especially for areas where EGC have only recently been detected such as the Salish Sea. EGC populations are well established on the west coast of Vancouver Island and in Sooke Basin but several detections have occurred recently in other parts of British Columbia (BC), including the Salish Sea.

To better understand the incursion of EGC into the Salish Sea, Fisheries and Oceans Canada’s (DFO’s) Ecosystem Management Branch (EMB) and DFO Science AIS programs worked with the Washington Department of Fish and Wildlife, Washington SeaGrant’s Crab Team, and University of Washington to develop a Salish Sea Transboundary Action Plan for Invasive European Green Crab. This plan lays out early detection (monitoring) recommendations but doesn’t specify how to identify or prioritize intertidal sites for EGC monitoring. Additionally, DFO's Aquatic Invasive Species National Core Program has been working to develop a monitoring program for the early detection of EGC throughout coastal BC, with a focus on the Salish Sea. Given the extreme spatial extent to be monitored, efforts must involve citizen science and Indigenous groups focusing on sites most likely to have EGC. Thus, prioritized monitoring sites for EGC in Canadian waters of the Salish Sea are urgently needed and the approach could be extended to other coastal areas in the future.

A variety of methods have been implemented by different users to identify suitable habitat for EGC at a range of spatial scales, but the outputs have not been evaluated in the context of EGC management nor for the Canadian portion of the Salish Sea specifically. Habitat suitability models have been developed for EGC along the west coast using MaxEnt, stochastic gradient boosted regression and classification models, and a qualitative site assessment and ranking tool (developed by the Washington SeaGrant Crab Team), all of which rely on different inputs and generate different response variables. Further, DFO Science developed a rapid site selection tool based on beach locations and habitat characteristics believed to be influencing invasion success. Each of these models will be evaluated to provide recommendations for EGC trapping sites in the Salish Sea. This will fulfil a need identified by Fisheries and Oceans Canada (DFO) AIS Management program and the assessment and advice arising from this Canadian Science Advisory Secretariat (CSAS) Regional Peer Review (RPR) will be used to inform EGC management in the Salish Sea and contribute to DFO’s international commitment related to the Bilateral EGC Action Plan.


The specific objectives of this review are to:

  1. Evaluate the strengths/weaknesses associated with four different methods of assessing habitat suitability for EGC, for the purpose of identifying potential monitoring sites in Canadian waters of the Salish Sea. Specifically reviewing: 1) MaxEnt; 2) Stochastic gradient boosted regression and classification models; 3) Washington SeaGrant’s Crab Team’s site assessment tool; and 4) DFO Science’s rapid site selection tool.
  2. Identify uncertainties in each of the tools evaluated in Objective 1.
  3. Identify sites for EGC monitoring in Canadian waters of the Salish Sea using the preferred method(s) evaluated in Objective 1.
  4. Characterize the feasibility of using the preferred method(s) to identify potential monitoring sites throughout coastal BC in the future.

Expected Publications

Expected Participation

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