 BACKGROUND:
A mature male Chinese Mitten Crab Eriocheir sinensis was collected June 9, 2006 at the mouth of the Patapsco River,
Maryland by a commercial waterman fishing crab pots. The crab was captured by Captain John Delp aboard
Bodacious. This is the first confirmed record for the Chesapeake Bay. The species is native to East Asia,
and is a potential invasive that could have negative ecological impacts. The Chinese mitten crab occurs in both
freshwater and saltwater. It is catadromous, migrating from freshwater rivers and tributaries to reproduce in
salt water. Young crabs spend 2-5 years in freshwater tributaries and can extend over 50 miles inland, potentially
above fall lines. Mature male and female crabs migrate downstream to mate and spawn in salt water estuaries.
The Chinese Mitten Crab is listed under the Federal Lacey Act which makes it illegal in the United States to import, export,
or conduct interstate commerce of this species without a permit.
Only a single animal has been captured in the Chesapeake Bay, and this may be an isolated occurrence. There are several
possible transfer mechanisms that could result in the delivery of a crab to local waters, without the species becoming
established. However, due to the documented ability of this species to invade and to establish itself in new areas,
Maryland Department of Natural Resources (MD DNR), the Smithsonian Environmental Research Center (SERC), the US Fish and
Wildlife Service (USFWS), and the National Oceanic and Atmospheric Administration (NOAA) have established
a joint effort to investigate the status of this species.
PLANNED RESPONSE:
MD DNR and partner agencies
are taking this encounter seriously. This watch statement has been circulated
to federal, state, county, municipal and private agencies and/or organizations
that are conducting sampling programs in the Chesapeake Bay watershed and potential mitten crab habitat. MD DNR
is also networking with commercial watermen, fish passage monitoring programs,
and with power companies that monitor species captured on cooling water intake
screens. This broad based monitoring is the first step to assessing if additional mitten crabs are present in the Bay habitat.
HOW TO IDENTIFY A MITTEN CRAB
Only crab in fresh waters of North America
Claws equal in size with white tips and “hair”.
If you find a crab without hair on the claws, it is NOT likely to be a mitten crab.
Carapace up to 4 inches wide; light brown to olive green in color.
No swimming legs. This crab has eight sharp-tipped walking legs.
CORRECTLY IDENTIFYING MITTEN CRABS
There is another species of
crab found in Maryland, which has been mistakenly identified as a Mitten Crab.
Small mitten crabs may be confused with the Harris mud crab, because of their
similar size and appearance.
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Harris Mud Crab Characteristics
- no notch between the eyes
- non-hairy, white-tipped claws
- ridges on back
- dull greenish-brown color
- maximum carapace width is 19 mm (¾ inch)
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Juvenile Mitten Crab Characteristics
- notch between the eyes
- claws may not be hairy if carapace width is less than 20 mm (¾ inch)
- claws are hairy by 25 mm (1 inch) carapace width
- four lateral carapace spines (fourth spine is small)
- smooth, round carapace or body shape
- legs over twice as long as the carapace width
- light brown color
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Identification photos courtesy of
California Department of Fish and Game |
WHAT TO DO IF YOU FIND A MITTEN CRAB
Do not throw it back alive!
Freeze the animal, keep on ice, or preserve it in rubbing alcohol, as a last resort.
Note the precise location where the animal was found.
If possible, take a close-up photo, as above.
Photos can be emailed to lfegley@dnr.state.md.us or to ruizg@si.edu for preliminary identification.
Include your contact information with photo.
If you cannot take a photo, contact Maryland DNR: Lynn Fegley (410-260-8285) or Smithsonian Environmental
Research Center(SERC): Greg Ruiz(443-482-2227)
REMEMBER THE LAW!
Never transport a live Mitten crab.
Mitten crab specimens are needed to confirm sightings, so please follow the instructions above, if you
find a mitten crab.
To learn more about mitten crabs see:
http://www.serc.si.edu/labs/marine_invasions/news/mitten_crab.jsp
http://www.wsg.washington.edu/outreach/mas/nis/mittencrab.html
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