Chinese Crabs Found in San Francisco Bay

A Chinese crab regarded as a delicacy in its native land has spread to California where scientists fear it could harm crops, levees and possibly the health of people who eat them.

Researchers at the Marine Science Institute netted five Chinese mitten crabs in south San Francisco Bay--enough to conclude the crabs are living and breeding and won’t disappear, biologists said.

“It could be bad news for the ecology, for farming, and the security of the levees” in the Sacramento-San Joaquin Delta, University of California marine biologist Andrew Cohen said last month.

Institute director Karen Grimmer said the crabs live in rivers and descend to the ocean to spawn. The only other organism in North America with such habits is the Atlantic river eel.

California banned the import of the crab in 1986. Scientists suspect someone intentionally released the crabs into the bay. The 6-inch-wide crab with hairy claws resembling mittens is the latest of about 200 imported species to establish a population in the bay-delta estuary.

The crabs spend most of their lives either in rivers or in the brackish water of upper estuaries, living in burrows dug in mud banks and feeding on a variety of plants and animals.

The mitten crab also carries Oriental lung fluke, a parasite that can be transmitted to people who eat inadequately cooked or pickled crab. The parasite causes lung problems similar to tuberculosis.