Damaging, Invasive Chinese Mitten Crab Found In Oregon For The First Time

Wildlife officials in Oregon say a highly invasive and damaging crab has been found in the state’s waters for the first time, decades after causing widespread damage in California.

The Oregon Department of Fish and Wildlife said a commercial fisherman caught a Chinese mitten crab on April 22 in the Lower Columbia River east of Tongue Point. It marked the first time a Chinese mitten crab has been confirmed in the Pacific Northwest. One Japanese mitten crab was found in the same are in 1997.

“A commercial fisherman who caught the unusual looking crab did the right thing by bringing it to ODFWs Columbia River staff,” the agency said, urging others to report any sightings with photos and exact locations.

Unlike any native crab species, mitten crabs have unusual features to look out for, including a notch between their eyes and four spines on each side of the carapace. They get their name from their hairy, mitten-like claws, and can range in color from brownish-orange to greenish-brown.

The Chinese mitten crab is a prohibited species, and officials believe have been introduced to the Columbia illegally by a person or from a ship’s ballast water as larvae.

The species caused “significant infrastructure and ecological damage” in San Francisco Bay in the late 1990s. Mature mitten crabs live in freshwater, but require brackish or salt water for reproduction and development. After hatching in saltwater in bays and estuaries, molted juveniles travel upstream of the salt water toward fresh water.

According to the U.S. Bureau of Reclamation, migrating mitten crabs can climb over tall locks and weirs to travel upstream, such as in the Sacramento River in the 1990s, or even leave the water to walk around them, terrain permitting. In some cases the crabs even possibly passed through locks and climbed up and down fish ladders.

ODFW biologists are working with the Washington Department of Fish and Wildlife and the National Oceanic and Atmospheric Administration to determine whether there are more mitten crabs in the Columbia River.