Invasive European Green Crabs

European green crabs are one of the most widespread invasive marine species on the planet, originally reaching Washington in 1996. When green crab populations grow too large, they compete with other shellfish, disturb the sediment, and destroy the eelgrass that is an important habitat for Dungeness crab and salmon.

Coastal Disaster

Exploding green crab populations threaten Washington's commercial and recreational shellfish industry. Recently, the Lummi Nation, the Makah Tribe, and Washington’s Governor all made disaster declarations because of the threat these invasive crabs pose to recreation, local economies, and Tribal culture.

Identifying the Green Crab

There are a few ways to identify a green crab. Surprisingly, their color is not the best one. Green crabs are most identifiable by their matching set of five marginal teeth, or spikes, along the front ridge of their shell.

Aggressive Invader

Green crab populations along Washington's coast and Puget Sound increased nearly 5,500% over two years between 2019 and 2021.

Sources

Background: Image of eelgrass. USGS

Map: Image of European green crab (Carcinus maenas). USGS/Hans Hillewaert

1 - https://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=190

2 - Salish Sea Transboundary Action Plan for Invasive European Green Crab, March 2019

3 - European Green Crab Increase Concerns, WA Dept of Fish & Wildlife, January 2022

Learn more at https://nas.er.usgs.gov/