Scientific name: Carcinus maenas
What Is It?
The European green crab is a small shore crab that is not necessarily green like its name implies. It typically is found in high intertidal areas and marshes in coastal estuaries and wave-protected embayments. It can live on a variety of surfaces including sand, mudflats, shells, cobble, algae, and rock. It is an opportunistic feeder and aggressive invader. It is native to the eastern Atlantic from Norway to North Africa.
Is It Here Yet?
Yes. As of 2023, European green crab infestations have been found along Washington’s Pacific Coast including near the Columbia River, Willapa Bay, Grays Harbor, and Makah Bay. Small populations of European green crabs have been found along the Strait of Juan de Fuca, in the San Juan Islands, and in northwest Washington bays around Bellingham and Anacortes. Lummi Sea Pond near Bellingham also has a sizable infestation. European green crabs have not been found in Puget Sound south of Hood Canal and central Whidbey Island or within Skagit Bay.
Why Should I Care?
The European green crab eats smaller crustaceans and many other plants and animals and can have dramatic negative impacts to native shore crab, clam, and oyster populations. Green crabs are believed to have caused the collapse of the soft-shell clam industry in New England. Their digging habits also have slowed eelgrass restoration efforts. European green crabs also may impact the health of shore birds by transmitting the worm Profilicollis botulus.
How Can We Stop It?
Emergency measures to control invasive European green crabs are well underway. In January 2022, Governor Jay Inslee issued an emergency proclamation that directed the Washington Department of Fish and Wildlife to implement measures to control European green crabs and to coordinate with other state agencies and tribes.
Trapping is the main tactic the department, tribes, shellfish growers, and partners are using to control these crabs. Washington Sea Grant leads a volunteer-based “Crab Team” that monitors for European green crab. This helps ensure early detection of the crabs in new locations.
For people who own beaches, tidelands or shellfish beds, support and permits for European green crab trapping may be available. Washington State is providing grants and other support to tribal co-managers, shellfish growers, and partners trapping European green crabs.
The public can help by looking out for European green crabs when at the beach or in shallow coastal water. Help prevent the spread by taking a photo, recording the location, and reporting it through the Washington Invasive Species App, the Washington Department of Fish and Wildlife reporting form, or by calling 1-888-WDFW-AIS.
The public should not kill suspected European green crabs at this time. This is to protect native crabs, who have been misidentified as green crabs and killed. The European green crab species is classified as a Prohibited Aquatic Animal Species in Washington, meaning they may not be possessed, purchased, sold, propagated, transported, or released into state waters.
What Are Its Characteristics?
- The best way to identify the European green crab is by the five spines on either side of their eyes. No other crab in Washington State has this characteristic.
- Juveniles are speckled with green, black, white, and rust.
- Adults vary in color from reddish to dark green, and are often mottled olive-brown with black and yellow spots.
- Adults’ undersides may be green, pale orange, or red.
- The adult male’s carapace grows up to 4 inches across.
- European green crabs are found along the shore, typically in less than 25 feet of water. They prefer areas protected from ocean waves or currents, such as mudflats, tidal sloughs, and river mouths (which are also known as estuaries).
How Do I Distinguish It From Native Species?
Despite the name, not all European green crabs are green. However, they can be distinguished from native shore crab species by the five spines located on both sides of the shell behind their eyes.
WISC= Washington Invasive Species Council
WDFW=Washington Department of Fish and Wildlife