Chinese Mitten Crab Found In Lower Columbia; First Confirmed In NW

THE FOLLOWING IS AN ODFW PRESS RELEASE

A Chinese mitten crab, a prohibited species in Oregon, was caught on April 22 in the Lower Columbia River east of Tongue Point. Chinese mitten crabs have not been confirmed in the Pacific Northwest until now. A single Japanese mitten crab was found in the same area in 1997. 

While this is a rare event in Oregon, mitten crabs caused significant infrastructure and ecological damage in and around San Francisco Bay when the population was at its height in the late 1990s. So, it is important to correctly identify this species and report it to your local ODFW office with the location found.

A commercial fisherman who caught the unusual looking crab did the right thing by bringing it to ODFW’s Columbia River staff. Staff then brought the crab to an ODFW shellfish biologist who identified it as a Chinese mitten crab.

Mitten crabs have unique features unlike any native crab species (see photo): they have a notch between their eyes and four spines on each side of the carapace. They are named for their hairy mitten-like claws and vary in color from brownish-orange to greenish-brown. Crab identification can be difficult and native crab have been misidentified as invasive.

Chinese mitten crabs spend most of their lives in freshwater, but adults must be in saltwater to reproduce. Newly hatched larvae are in open saltwater in bays and estuaries and fully molted juveniles are found in brackish and freshwater areas within a few miles upstream of saltwater.

This single crab was a large male that could have been introduced to the Columbia illegally by a person or via ballast water as larvae.

ODFW encourages Columbia River users to keep an eye out for mitten crab and report any found to ODFW along with photos if possible and location, or report it online to the Oregon Invasive Species Council.

ODFW biologists are working with the Washington Department of Fish and Wildlife and NOAA to determine if other mitten crabs are in the Columbia River. Methods include setting up trap lines and potentially collecting water and substrate samples to look for environmental genetic markers specific to the mitten crab.