Chinese Mitten Crab (Eriocheir sinensis)
What is it?
FACT: Chinese mitten crabs spend approximately 90% of their life in freshwater.
Where is it from & where is it now?
As its common name suggests, the Chinese mitten crab is native to the pacific coast of China and Korea.
The first notable invasion of Chinese mitten crab occurred in Germany in the early 1900’s. It has since plagued a number of Northern European countries, as well as areas in Western Asia (Iran and Iraq), Canada and North America. The first confirmed sighting of Chinese mitten crab in the US occurred in the Great Lakes in 1965. Since this time, mitten crabs have been found in Chesapeake Bay, Delaware Bay, Hudson River, Mississippi River, San Francisco Bay, and the Columbia River. The only self-sustaining population of mitten crab is currently found in San Francisco Bay, California. It remains unclear whether mitten crab have established a population in the mid-Atlantic region.
FACT: Single specimen of mitten crab have been captured in the Columbia River near Portland Oregon (1999) and Columbia River Estuary near Port of Ilwaco (1997).
How did it get here?
It is believed Chinese mitten crab were introduced to the US in one of two ways. They may have been released intentionally to create a fishery and provide a food resource (in Asia, the mitten crab is a delicacy), or the juveniles (free floating larvae) were introduced to our waters accidentally through the transport of contaminated ship ballast water.
Today the mitten crab is still spread through ballast water discharge, intentional stocking, and by commercial or recreational boating activities. Once introduced to a new location, it is possible the crab can migrate to surrounding water bodies on its own.
FACT: This creepy crustacean can migrate up to 11 miles per day and will even travel on dry land to avoid barriers such as dams and levees.
What are its impacts?
FACT: Female mitten crab produce 250,000 to 1 million eggs per brood.
What is being done about it?
A number of control methods such as trapping, trawling, physical barriers, and harvest programs have been used to battle this mitted monster with limited success. Chemical controls are generally not considered a viable option to combat mitten crab because of their mobile nature. However, research on a fungus that is lethal to mitten crab may prove to be an effective biological control agent in the future. For now, federal legislation (Federal Lacey Act) has made it illegal to import eggs and live mitten crab to the United States. It is also illegal to transport or possess live mitten crab in the states of California, Washington, and Oregon (OAR 635-056).
Public outreach and education remains the best most cost effective method of preventing the introduction and spread of Chinese mitten crab.
FACT: English researchers have considered selling invasive Chinese mitten crab to restaurants and markets as a way to control their numbers.
How can YOU prevent the spread of Chinese mitten crab?
Aquatic nuisance species have the uncanny ability to hitch a ride in places we least expect them. To minimize the potential spread of unwanted invaders, follow these simple steps.
· CLEAN: your boat and all your gear including waders and boots after each use.
· DRAIN: all of the water from your boat (including the bilge, live well, motor), trailer, tackle and gear before leaving the area.
· DRY: your gear completely (at least 48 hours) after each use.
· NEVER: move live organisms from one water body to another – it is illegal!
· If you happen to capture a mitten crab, DO NOT throw it back alive. Take a photograph, freeze it or preserve it in rubbing alcohol, and report your finding to a local authority.
What if I find a mitten crab?
If you find Chinese mitten crab or any other “tenacious trespasser” contact the Aquatic Nuisance Species Task Force at 1-877-STOP-ANS. If you spot a potential aquatic invader in Oregon, contact the Oregon Invasive Species Hotline at 1-866-UNVADER. In Washington State you can report a potential sighting at 1-877-9-INFEST.
Submitted by Jen Poirier