In recognition of National Invasive Species Awareness Week (Feb. 28-March 4), we wanted to call attention to a relatively new threat in the waters off the coast of Washington – the European green crab.
Invasive Green Crabs Pose Threat to Washington’s Shellfish Industry and Tribal Culture
European green crabs are one of the most widespread invasive marine species on the planet. Where they are abundant, green crabs outcompete other native shellfish. They are voracious eaters and a major predator of clams, mussels, and oysters. One study suggests that a single green crab can eat around 22 clams per day. They also actively disturb bed sediments, leading to the loss of the eelgrass that serves as essential habitat for Dungeness crab and Pacific salmon.
In 2021, more than 102,000 European green crabs were caught in Puget Sound and along Washington’s coast. This was an astronomical 5,500% increase from the 1,800 crabs caught just two years earlier in 2019. In response to the explosion in the green crab population, a series of disaster declarations were made by the Lummi Nation and the Makah Tribe concerning the green crabs’ impact on Tribal culture and economy. Washington State Governor Jay Inslee followed suit and issued an emergency order to mobilize state resources.
To help protect against invasive European green crabs, many partners including the Washington Department of Fish and Wildlife, Lummi Nation, Makah Tribe, Shoalwater Bay Tribe, Stillaguamish Tribe of Indians, Washington Sea Grant, National Oceanic and Atmospheric Administration, Environmental Protection Agency, Bureau of Indian Affairs, U.S. Fish and Wildlife Service, and U.S. Geological Survey have been participating in a green crab monitoring network along the Pacific Coast and Puget Sound. Over the last few years, the coordinated program has successfully detected and eradicated small colonies of the invasive crab. However, the recent discoveries of large colonies of over 86,000 green crabs in Lummi Sea Ponds show how vulnerable the Puget Sound and Washington’s coast are to a major infestation.
The recent increase in European green crab populations combined with multiple Tribal disaster declarations has galvanized collaboration between the Bureau of Indian Affairs, U.S. Geological Survey, and U.S. Fish and Wildlife Service to leverage funding, resources, and technical expertise to improve detection, increase control efforts and pursue eradication, where possible, of the invasive crabs.
Recognizing the seriousness of the threat to Tribal cultural and natural resources, the Bureau of Indian Affairs remains committed to working with the Tribes, state, and federal partners to address the invasive green crabs. The Bureau has supported the Tribes through recent years, prioritizing nearly \$670,000 on its Invasive Species Program to target the European green crab in multiple Tribal waters for survey, control, and management efforts.
“Protecting cultural resources and the habitat that depends on having balanced ecosystems to thrive is a key part of meeting our trust responsibilities to the Tribes,” said Bryan Mercier, BIA Northwest Regional Director. “By working with our partners, we are all better positioned to stop the spread of these invasive crabs.”
For National Wildlife Refuges, the U.S. Fish and Wildlife Service conducts early detection, monitoring, control, and removal trapping of European green crab. These efforts are occurring at Billy Frank Jr. Nisqually National Wildlife Refuge Complex in south Puget Sound; the Washington Maritime National Wildlife Refuge Complex in Puget Sound and the Strait of Juan de Fuca; and Willapa National Wildlife Refuge Complex in southwestern Washington.
“Detecting green crab populations is essential for limiting their spread,” said Theresa Thom, U.S. Fish and Wildlife Service Regional Aquatic Invasive Species Coordinator. “Thanks to ongoing monitoring, we have a better chance of finding the crabs early so we can remove them quickly.”
In 2018, the U.S. Fish and Wildlife Service provided about \$82,000 to the Makah Tribe to address the green crab population at the Makah Indian Reservation. This included assessing the extent of the crabs, controlling their population growth, and providing training to Tribal staff to continue and expand control efforts. In 2021, the U.S. Fish and Wildlife Service provided about \$71,000 to the U.S. Geological Survey to assess the trapping effort needed for the early detection of the green crabs.
The U.S. Geological Survey is working to increase the effectiveness of Washington’s green crab early detection and rapid response program. Research conducted at the U.S. Geological Survey Western Fisheries Research Center aims to improve native shellfish habitat and limit the spread of European green crabs in coastal waters. Scientists have added new molecular technologies to the current monitoring program to broaden its capabilities. New research also looks at the compounding effects of climate change on the green crab populations (e.g., warmer waters = more green crabs). Ultimately, this work will help collaborators better control the spread of green crab and protect our region’s vital ecosystem, culture, and fisheries economy.
Did You Know
- Washington shellfish industry employs more than 3,200 people and provides $270 million to the Washington economy.
- European green crabs were first discovered in Washington at Grays Harbor in 1996.
- Not all European green crabs are green. Some can be yellow, brown, or even red.
- Green crabs readily feed on smaller Dungeness crabs, as well as oysters, clams, and mussels.
- European green crabs are edible but typically considered too small to be viable for food.
- There are more than 6,500 invasive species established across the United States.
- U.S. Fish and Wildlife Service: Invasive Species
- U.S. Geological Survey: Invasive Species Program
- Emergency Declaration: Washington Governor's Office
- Green Crabs Invade Sound: Lummi Nation
Established in 1879, the U.S. Geological Survey has evolved over the decades, matching its talent and knowledge to the progress of science and technology. The Survey is the primary science agency for the Department of the Interior. It is sought out for its natural science expertise and its vast earth and biological data collection. Their mission is to monitor, analyze, and predict current and evolving dynamics of complex human and natural Earth-system interactions and to deliver actionable information to decision makers.
The U.S. Fish and Wildlife Service is the only agency of the U.S. government whose primary responsibility is the conservation of the nation’s fish, wildlife, and plants. Because of their responsibilities, the Service is very concerned about invasive species’ impacts across the nation. Invasive plants and animals have many impacts on fish and wildlife resources. Invasive species degrade, change, or displace native habitats, compete with our native wildlife, and are thus harmful to our fish, wildlife, and plant resources.
The Bureau of Indian Affairs protects, develops, manages, and enhances Indian trust resources for the benefit of American Indian and Alaska Native peoples. Targeting such a prolific invasive species such as the European green crab is critical for preventing the crabs from destroying fish and shellfish facilities, which the Lummi Nation and many other Pacific Northwest Tribes depend on for their spiritual, economic, and cultural needs.