|Status & Synopsis||Economic Value of Potentially Affected Fisheries||Geographic Distribution||PSMFC Funded Projects|
Image by: Lee Mecum, California Fish and Game
The genus Eriocheir is listed as an injurious species under the federal Lacey Act, which bars the importation and interstate transport of live crabs. The Chinese mitten crab is on the list of 100 Most Dangerous Invaders to Keep Out of Oregon (2006). It is a prohibited species in Washington, Oregon and California.
The Chinese mitten crab is a burrowing species native to the coastal rivers and estuaries of the Yellow Sea (Asia), with a native distribution from the province of Fukien, China, northward to the Korean Peninsula (~26°N northwards to ~ 40°N). Chinese mitten crabs are established in England and most of Europe, including Russia. They also have been found in the Chesapeake Bay (Patapsco River, Maryland in 2005 and 2006), the St. Lawrence River and periodically since 1965, in the Great Lakes (O’Neill and MacNeill 2005).
The Chinese mitten crab is a catadromous species (living in fresh water but migrating to marine/estuarine waters to breed). Juveniles can migrate upstream several hundred miles. The crabs are believed to have one reproductive season and die shortly after reproduction (Panning 1939).
The Chinese mitten crab was first discovered in San Francisco Bay in the winter of 1992 (Rudnick et al. 2003). It is likely that mitten crabs arrived in the Bay, as well as in other parts of the continent, either through the discharge of contaminated ballast water or as a result of the release of live adult crabs imported for sale in local Asian markets (Cohen and Carlton 1997).
A population of mitten crabs in the Columbia River has yet to be confirmed, but there have been reported sightings. A sturgeon angler near Astoria caught a male Japanese mitten crab (E. japonica) in July 1997. In September 1999, a mitten crab was reportedly caught by a crayfish fisherman under the Sauvie Island Bridge over the Multnomah Channel, near Portland. The crayfish fisherman recognized the uniqueness of the crab when he caught it and gave it to another individual who placed it in a pond. The pond was later drained and cleaned, but the crab was no longer present. The crayfish fisherman was shown a preserved mitten crab and viewed a video about the crab. He confirmed that the crab he caught was a mitten crab (Sytsma 2000).
Mitten crabs pose ecological, economic, and human health concerns. Following their introduction into California, it was feared that the Chinese mitten crabs were a secondary host for a dangerous lung fluke that can infect humans and that has caused deaths in Asia (Dugan et al. 2002). However, results of a study conducted by researchers at the University of California, Santa Barbara, suggested that Chinese mitten crabs in the San Francisco Bay estuary were not infected with the ling fluke. Another concern about the Chinese mitten crab is its high burrowing density, which has been linked with bank and levee weakening, and even collapse in some areas where this species has been introduced (Panning 1939, Dutton and Conroy 1998).
The most severe impacts in California have been at water engineering projects where the crabs have clogged fish salvage facilities. In 1998, the Bureau of Reclamation, at its Tracy California Central Valley Project pumping plants, collected about 1 million crabs. It appears that there are still significant numbers of mitten crabs in and around San Francisco Bay and its tributaries, but the number of mitten crabs in the Sacramento-San Joaquin Rivers Delta now appears to be at a historic low (Bergendorf 2005).
Fish passage facilities, such as fish ladders, may also be impacted by the mitten crab. One study suggests (Culver 2005) the mitten crab may represent a significant threat to salmonid eggs and larvae through direct consumption. The crab’s foraging activity could also result in the indirect mortality of salmonid eggs and larvae by exposing the eggs and larvae to other predators and/or unfavorable conditions (Culver 2005).
One study has shown that few estuaries in the Pacific Northwest are likely to develop large mitten crab populations. However, Puget Sound and Coos Bay could have the proper combination of temperature, salinity and retention time for mitten crab establishment (Hanson 2005).
Source: U.S. Geological Survey (USGS)
Bergendorf, David. 2005 Personal Communication. US Fish and Wildlife Service. Stockton, California
CALFED Ecosystem Restoration Program Plan. 1998. CALFED Bay-Delta Program.
Cohen, A and J Carlton. 1998. Accelerating invasion rate in a highly invaded estuary. Science 279: 555-558.
Dugan, Jenifer E., Mark Walter, and Carolynn Culver. 2002. Evaluating the health risk posed by the invasive Chinese mitten crab. Final Report to National Sea Grant Aquatic Nuisance Species Research and Outreach Project R/CZ-160.
Dutton, C and C Conroy. 1998. Effects of burrowing Chinese mitten crabs (Eriocheir sinensis) on the Thames tideway. Environment Agency. London, U.K.
O’Neill, Chuck and David MacNeill. 2005. NYSG Educating river residents regarding potential for invasive species new to northeast; Enlist Aid In Spotting Chinese Mitten Crab. New York Sea Grant. Brockport, NY.
Pacific Fishery Management Council. 2004. Review of 2003 Ocean Salmon Fisheries. Portland, Oregon. 317 pp.
Panning, A. 1939. The Chinese mitten crab. Smithsonian Institution annual report for 1938, Washington, D.C.
Rudnick, Deborah A., Kathryn Hieb, Karen F. Grimmer, Vincent H. Resh. 2003. Patterns and processes of biological invasion: The Chinese mitten crab in San Francisco Bay. Basic Appl. Ecol. 4, 249-262
Sytsma, Mark. 2000. Personal Communication. Center for Lakes and Reservoirs, Portland State University. Portland, Oregon