This new menace to the West Coast threatens water distribution, agricultural production, flood protection, fish passage, salmon production, and coastal river systems across the United States. The mitten crab, named for its furry claws, was first seen in San Francisco Bay in 1992, but its population has exploded and its distribution is expanding. In California, millions of migrating mitten crabs have clogged irrigation systems and interrupted important fish passage operations. Mitten crab burrows weaken levees and increase bank erosion. Another scarey observation, particularly for Alaska, is that mitten crabs can feed directly on the redds (nests) of spawning salmon.

In their native range, mitten crabs (particularly their eggs) are considered something of a delicacy – but they can be hazardous to your health! Persistent spitting of blood, breathlessness, chest pain, brain lesions and calcifications, partial paralysis, epilepsy, clubbed fingers, and lung cysts (see image) are all potential symptoms of Paragonimiasis – the disease caused by ingestion of live lung flukes in raw or partially-cooked mitten crabs. These worms have not yet been found in West Coast populations of mitten crabs, but would you want to take a chance!?

For more information on the mitten crab invasion in California:

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If you catch a mitten crab in Alaska, do not throw it back alive! Preserve it in rubbing alcohol or freeze it, note the precise location in which you found it, and contact the Invasive Species Program Coordinator for either the U.S. Fish and Wildlife Service (907-786-3813) or the Alaska Department of Fish and Game at their toll free number: 1-877-INVASIVE (1-877-468-2748).