Animal Crustaceans
Family: Grapsidae
Classification: Prohibited
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:
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