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To report an AIS
sighting or to find out
more information call
1-888-WDFW-AIS

Questions or comments regarding the state's Aquatic Invasive Species and Ballast Water Management Programs may be directed to:

Allen Pleus
AIS Coordinator
(360) 902-2724
Allen.Pleus@dfw.wa.gov

 
View WAC 220-12-090
Classification - Nonnative aquatic
animal species with photos

Eriocheir sinensis (Chinese mitten crab)

Animal Crustaceans
Family: Grapsidae
Classification: Prohibited

Chinese Mitten Crab

Mitten crabs are the only freshwater crabs in North America. They are easily identified because of their hairy claws. First discovered in San Francisco Bay in 1992, they rapidly spread to the Sacramento and San Joaquin rivers. The crab spend most of their lives in freshwater, then migrate to salt water to reproduce. These massive migrations have clogged fish screens and hampered water delivery in Northern California. The crabs burrow for protection, weakening levees and increasing erosion of banks. The crabs are know to eat Salmon, Trout and Sturgeon eggs, and may pose a serious threat to ecosystems and fisheries along the West Coast. They may pose a human health threat because they can carry the oriental lung fluke, and are considered a delicacy by many Asian populations, who eat them uncooked.

One live mitten crab was found in the Columbia River in 1997. Although there have been reports of sightings, mostly by fishermen (the crab are bait thieves) none have been captured.

The Chinese mitten crab was first discovered in San Francisco Bay in 1992. It has since become well established in the Sacramento and San Joaquin rivers, where massive migrations clog fish screens and impede water delivery. The crabs burrow for protection from predators, which can weaken levees and increase erosion. The crab is also an intermediate host to a human parasite the oriental lung fluke.

The crabs live in freshwater most of their lives, returning to the saltwater to reproduce and die. They have been known to migrate up to 800 miles inland, leaving the water to walk around obstacles. Young crabs eat mostly vegetation, while mature crabs prey upon other animals.

A single male Japanese mitten crab (Eriocheir japonica) was found in the Columbia River in 1997. Other sightings have been reported since, although none have been captured. Fishermen are often the first to see the crab, because they are aggressive bait stealers.

Your help is needed to report sightings and prevent the spread of this species. If you find one, preserve it in rubbing alcohol or freeze it. Do not release it. Note the precise location where you found it. For more information on Chinese mitten crab visit: