The European green crab (Carcinus maenas) is a globally damaging invasive species that poses a threat to native shellfish, eelgrass, and estuary habitat critical for salmon and many other species.

The green crab, Carcinus maenas, is a widely distributed invasive species that eventually alters its new environment. It's assumed that such species have high genetic diversity, or a variety of characteristics allowing them to adapt and thrive. But the green crab has low genetic diversity, while still spreading rapidly in a new part of the world.

Considered one of the most invasive marine species on the planet, the European green crab (Carcinus maenas) severely impacts any ecosystem it invades. Found in San Francisco Bay around the late 1980s, the green crab has made its way to Oregon and Washington, causing concern for the preservation of native crab, oyster, and clam species.

C. maenas is a widespread invasive species, listed among the 100 of the World's Worst Invasive Alien Species. It is native to the north-east Atlantic Ocean and Baltic Sea, but has colonised similar habitats in Australia, South Africa, South America and both Atlantic and Pacific coasts of North America.