Salish Sea Transboundary Action Plan for Invasive European Green Crab


Published: February 2019

Revised: March 2019

Pages: 55

Author(s): Joan Drinkwin, Allen Pleus, Dr. Thomas Therriault, Renny Talbot, Dr. Emily W. Grason, Dr. P. Sean McDonald, Jeff Adams, Todd Hass, Kate Litle

Executive Summary

The purpose of the Salish Sea Transboundary Action Plan for Invasive European Green Crab (Plan) is to establish and implement a coordinated and collaborative response to incursions of European green crab that pose a risk of harming or threatening the environmental, economic, or human resources within the shared waters of the Salish Sea.

European green crab (EGC) is a globally-damaging invasive species that has produced a variety of ecological and economic impacts on temperate coastal shorelines worldwide. Prolific and gregarious, EGC are known to disturb native habitat, displace resident species, and alter natural food webs, when abundant. Additionally, EGC predation has caused significant harm to shellfish industries in some regions.

The EGC is a notorious aquatic invasive species, able to survive a wide range of temperatures and salinities. To reproduce, individual EGC are capable of releasing hundreds of thousands of larvae that can live up to 80 days and travel hundreds of kilometers on ocean currents. It is a generalist feeder, digging in the sediment for bivalves and other prey and has been linked to:

  • Massive declines in commercial bivalve crops (reducing softshell clam landings from 15.4 million pounds or 7 million kilos to 2.3 million pounds or 1 million kilos) on the east coast of the U.S., contributing to fishery collapse (Glude 1955);
  • Decimation of native clams and shore crabs in at least one California embayment causing alterations of the food web (Grosholz et al. 2000); and
  • Substantial reduction (up to 75%) in eelgrass density in Nova Scotia and Newfoundland (Garbary et al. 2014; Matheson et al. 2016).

Potential impacts of an EGC invasion in the Salish Sea include degradation and destruction of eelgrass and estuarine marsh habitats, threats to the harvest of wild Salish Sea shellfish and the shellfish aquaculture industry, threats to the Dungeness crab fishery, threats to salmon recovery (and by extension threats to orca recovery), and a complex array of additional ecological impacts to food webs, all of which negatively impact the human uses and cultural resources of the Salish Sea. Because EGC poses risks to the economy, ecology, and cultural food resources of the Salish Sea, it is classified as a prohibited level 1 species in Washington State and as a control species by the Department of Fisheries and Oceans Canada.

Within the Salish Sea, the range and abundance of EGC is still quite limited, and to date the only established (self-sustaining) population occurs in Sooke Basin, British Columbia. As of October 2018, small numbers of EGC have been found at several other locations in British Columbia and Washington State. Now is our best chance to manage EGC in the Salish Sea to avoid the calamitous results of EGC invasions seen elsewhere around the world. There is no better time to prevent invasive harm than through a successful process of early detection, rapid response and proactive adaptive management.

The current response to early detections of EGC in Washington State waters of the Salish Sea is a success story seldom seen in the world of Aquatic Invasive Species (AIS) management. Rather than playing ‘catch up', we still appear to be ahead of the curve and are working aggressively to understand, identify and prevent incursions of EGC before they take hold and cause the dramatic impacts to the Salish Sea ecology and shellfish industry that have been seen on the East Coast of the United States and elsewhere around the globe. The coordinated, science-based adaptive response involves a team of dedicated partners executing geographically-broad, intensive trapping efforts. These ongoing management actions are designed to keep incursions within manageable size to avoid massive larval spread to other parts of the Salish Sea and in situ harm to local ecosystems.

Using lessons learned from successful early detection and rapid responses, this Salish Sea Transboundary Action Plan for Invasive European Green Crab lays out clear actions to be taken to prevent and/or minimize harm to the environmental, economic, and human resources of the Salish Sea as a whole from an invasion of European green crab.

This action plan focuses on six objectives calling for:

  • Collaborative management;
  • Prevention of human-mediated introduction and spread;
  • Early detection;
  • Rapid response to newly detected incursions;
  • Control of infested sites; and
  • Strategic research to improve adaptive management.

Washington Department of Fish and Wildlife (WDFW), Department of Fisheries and Oceans Canada (DFO), and Transport Canada are the key regulatory managers of potential human-mediated introduction and spread of EGC through their respective Aquatic Invasive Species programs. Washington Sea Grant's (WSG) Crab Team program, in coordination with WDFW, plays a major role in early detection and rapid response by training and supporting hundreds of volunteers and agency and tribal staff to monitor sites for early detection.

The actions laid out in this plan follow WDFW's and DFO's legal authority and mandate to lead the response to EGC in the Salish Sea. The estimated costs of implementing this plan for the Washington State 2019-21 fiscal year biennium (July 1, 2019 to June 30, 2021) and projections for future years will be addressed in a separate budget document.

There is still opportunity to avoid major impacts from EGC in the Salish Sea by continuing decisive and aggressive actions to contain populations and to prevent further introduction and spread of EGC in other parts of the Salish Sea.

Suggested citation

Drinkwin, J., Pleus, A., Therriault, T., Talbot, R., Grason, E.W., McDonald, P.S., Adams, J., Hass, T., Litle K., 2019. Salish Sea Transboundary Action Plan for Invasive European Green Crab. Puget Sound Partnership.