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Warning of Chinese crabs on the march
Yorkshire Post Today ^ | 08 February 2006 | Dave Mark

Posted on 02/08/2006 8:02:32 AM PST by Willie Green

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To: edpc

Chinese Mitten Crab

What is the Chinese mitten crab?

The Chinese mitten crab (Eriocheir sinensis) is a burrowing crab whose native distribution is the coastal rivers and estuaries of the Yellow Sea in Korea and China. It has recently become established on the west coast of the U.S. in the San Francisco Bay/Delta watershed in California, posing a potential threat to native invertebrates and to the ecological structure of freshwater and brackish estuarine communities, as well as disrupting some fish and shrimping operations. Although not currently present in the Pacific Northwest, scientists predict that, like the European green crab (Carcinus maenas), it is likely to arrive in Oregon and Washington eventually through larval dispersal or intentional release.

Note: It is illegal to import eggs or live specimens of any species of mitten crab (genus Eriocheir) to the United States under the Federal Lacey Act. It is also illegal to import, transport, or possess live Chinese mitten crabs in California, Washington, and Oregon.

What does the crab look like and where does it live?

The main identifying features of the mitten crab are the dense patches of hairs on the white-tipped claws of larger juveniles and adults, hence the name mitten crab. The claws are equal in size, the shell (carapace) has four spines on either side, and reaches a width of approximately 3 inches (80 mm). The legs of the adult crab are generally more than twice as long as the width of the carapace. A catadromous species, the adults migrate downstream to reproduce in the brackish waters of estuaries. The females carry 250,000 to 1 million eggs until hatching, and both sexes die soon after reproduction. After a 1-2 month period as planktonic larvae, the small juvenile crabs settle out in salt or brackish water in late spring, then migrate, often long distances, to freshwater to rear. In China's Yangtze River, mitten crabs have been reported 800 miles upstream from the Yellow Sea.Chinese Mitten Crab

 

Mitten crabs are omnivores, eating both plants and animals. Juveniles eat primarily vegetation. As they mature, the crabs increasingly prey upon animals, especially small invertebrates including worms and clams. In California, adult crabs have become a major nuisance to anglers, taking a variety of baits ranging from ghost shrimp to shad. Predatory fishes, including sturgeon, striped bass and channel catfish, as well as bullfrogs, raccoons, river otters and wading birds may prey upon the crab.

Mitten crabs are adept walkers on land, and if blocked by dams, weirs or other obstructions during their migration, move readily across banks or levees to bypass them. In Germany, large numbers of mitten crabs left the water at night when they encountered an obstruction, and occasionally wandered the streets and entered houses. In California, mitten crabs have been found on roads and airport runways, in parking lots, yards and swimming pools.

 

A single male Japanese mitten crab (Eriocheir japonica) was caught in the Columbia River, Oregon in 1998. The species is very similar to the Chinese mitten crab currently found in California, and its presence was most likely the result of someone's attempt to introduce it to the watershed.

A successful invader

The Chinese mitten crab has a long history as an invader. The crab was accidentally introduced to Germany in the early 1900s. In the 1920s and 1930s, the population exploded and the crabs rapidly expanded their distribution to many northern European rivers and estuaries. Most recently, the River Thames in England has experienced a population explosion of the crabs.

In 1992, commercial shrimp trawlers in southern San Francisco Bay collected the first mitten crabs on the West Coast. Since then, the mitten crab has spread rapidly, established in the San Francisco Bay, and spread to river areas upstream of the Delta. The most probable mechanism of introduction to the estuary was deliberate release to establish a fishery (in Asia, the mitten crab is a delicacy and crabs have been imported live illegally to markets in Los Angeles and San Francisco) or accidental release via ballast water.

Mitten crab population control has been attempted but there is little available information on the results. Mitten crab populations decreased in Europe in the late 1940s, coinciding with an increase in water

Why should we be worried?

 

The mitten crab poses a potential human health threat. It is an intermediate host for the Oriental lung fluke, and mammals, including humans, can become infested by eating raw or poorly cooked mitten crabs. However, neither the lung fluke nor any of the freshwater snails that serve as the primary intermediate host for the fluke in Asia have been found in the Pacific Northwest or California.

An expanding mitten crab population poses several ecological, economic and human health threats. The mitten crab may have a profound effect on biological communities through predation and competition, and could change the structure of fresh and brackish water benthic invertebrate communities in areas they invade. Also of concern is potential predation on salmonid and sturgeon eggs and juveniles. In tidal areas, mitten crabs burrow into banks for protection from predators and desiccation during low tides. This burrowing activity may increase erosion and instability of levees and riverbanks. Mitten crabs, a host for the Oriental lung fluke, are also a human health concern. In addition, mitten crabs often inhabit areas that may contain high levels of contaminants. Bioaccumulation of contaminants could be transferred to predators, including humans.

In Europe, the most widely reported economic impact of mitten crabs has been damage to commercial fishing nets and to the catch when the crabs are caught in high numbers. In San Francisco Bay, removing the crabs from the nets has been time-consuming and costly to shrimp trawlers (one trawler has reported catching over 200 crabs in a single tow several times), damaging or killing the catch. Another significant problem in California has been the impact on diversion and fish salvage facilities. Mitten crabs have clogged pumps, screens, and intakes and have damaged and killed fish at salvage facilities associated with water diversions. With the declines in salmon and trout populations, any further disruption or damage to fish passage is a major concern.

What other information is available on mitten crabs?

More information about the mitten crab, including an identification guide, can be found on California Department of Fish and Game's Central Valley Bay-Delta Branch web site at The following link will open in a new window. http://www.delta.dfg.ca.gov under the Biological Resources section, or at the San Francisco Estuary Institute website, The following link will open in a new window.http://www.sfei.org/invasions.html.

For general information on non-indigenous species, contact the Pacific Northwest Marine Invasive Species Team (MIST): Paul Heimowitz, Oregon Sea Grant, 503.722.6718 or Nancy Lerner, Washington Sea Grant Program, 206.616.8403. Or visit the Washington Sea Grant Program web site at http://www.wsg.washington.edu.

 

51 posted on 02/08/2006 8:44:18 AM PST by dennisw ("What one man can do another can do" - The Edge)
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To: N3WBI3

The body of this crab looks to be barely 3 inches across. That's a whole lot of pickin and not much finger lickin. They'd probably make a great compost. I'm thinking HUGE tomatoes!


52 posted on 02/08/2006 8:47:35 AM PST by WideGlide (That light at the end of the tunnel might be a muzzle flash.)
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To: N3WBI3

Herrow!


53 posted on 02/08/2006 8:48:40 AM PST by PzLdr ("The Emperor is not as forgiving as I am" - Darth Vader)
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To: Tijeras_Slim

It's the Chinese version of the old Roger Corman flick, "Attack of the Crab Monsters".


54 posted on 02/08/2006 8:50:06 AM PST by PzLdr ("The Emperor is not as forgiving as I am" - Darth Vader)
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To: OKIEDOC

"I always wondered if the Chinese had crabs."

FUNNY! (not)


55 posted on 02/08/2006 8:53:35 AM PST by BigChineseMan
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To: PzLdr

"Herrow!"

Ha!


56 posted on 02/08/2006 8:55:08 AM PST by BigChineseMan
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To: All
Image hosting by TinyPic
Natural habitat of a more common crab.
57 posted on 02/08/2006 8:55:24 AM PST by Old Seadog (Inside every old person is a young person saying "WTF happened?".)
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To: ButThreeLeftsDo
From The National Geographic article you posted the link for

""The Chinese love them, especially when they're full of gonads during the breeding season."

Ugh, wish I hadn't read that part.

58 posted on 02/08/2006 9:09:59 AM PST by #1CTYankee (That's right, I have no proof. So what of it??)
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To: #1CTYankee

I was wondering who was going to be the first to stumble on that tasty morsel.....


59 posted on 02/08/2006 9:12:09 AM PST by ButThreeLeftsDo (Carry Daily, Apply Sparingly.)
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To: ButThreeLeftsDo
"I was wondering who was going to be the first to stumble on that tasty morsel....."

How does one get full of gonads anyway?

Never mind, I don't want to know.

60 posted on 02/08/2006 9:17:42 AM PST by #1CTYankee (That's right, I have no proof. So what of it??)
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To: the gillman@blacklagoon.com
Don't know what you do for a living, but your question tells me that you are several orders of magnitude sharper than the author of this article...
61 posted on 02/08/2006 1:18:57 PM PST by Publius6961
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To: Joe 6-pack

LOL


62 posted on 02/08/2006 1:50:30 PM PST by OKIEDOC (There's nothing like hearing someone say thank you for your help.)
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To: Willie Green
Chinese "Mitten crabs."
63 posted on 02/25/2007 5:06:14 PM PST by UnklGene
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To: UnklGene

Willie be banned for sometime now.


64 posted on 02/25/2007 5:07:59 PM PST by johniegrad
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To: dennisw

What about the intentional releasing. Why are the orientals doing that?


65 posted on 02/25/2007 5:13:27 PM PST by Jason_b
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To: Willie Green

What are with the crab posts tonight? First it is the Pacific crabs over running Norway and the Barents Sea, then this! Let's draw the butter and be done with 'em! Crabs are good eatin' in my book!


66 posted on 02/25/2007 5:45:38 PM PST by oneamericanvoice (Attack of the giant crabs! Not the movie!)
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To: the gillman@blacklagoon.com
Even if the crabs were not good to eat, they could certainly be used as fertilizer. Just grind them up and spread them over the rice paddies.

Back in the days of the Pilgrims, before they realized how good lobsters were to eat and how much money they could make off tourists by opening overpriced nautical-themed restaurants, they would use lobsters to fertilize their corn fields.

67 posted on 02/25/2007 5:50:45 PM PST by SamAdams76 (I'm 23 days from outliving Steve Irwin)
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To: Willie Green

welcome back...


68 posted on 02/25/2007 5:53:27 PM PST by sit-rep ( http://trulineint.com/latestposts.asp)
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To: All
Even though it's an old thread, I just have to post this.


69 posted on 02/25/2007 5:58:12 PM PST by COEXERJ145 (Bush Derangement Syndrome Has Reached Pandemic Levels on Free Republic.)
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To: Willie Green
"Newcastle University researchers have warned there could be a population explosion of the creatures."

Maybe WHO, PETA, and Green Peace activists could distribute condoms.

Alert Richard Branson, Prince Philip, and Bob Geldof!

70 posted on 02/25/2007 6:06:01 PM PST by HowlinglyMind-BendingAbsurdity
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To: Willie Green

Just tell the Muslims they taste like sheep.


71 posted on 02/25/2007 6:08:26 PM PST by Redleg Duke (Heaven is home...I am just TDY here!)
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To: caver

You need a razor, a can of lighter fluid, a lighter and a mess kit knife....


72 posted on 02/25/2007 6:10:04 PM PST by Redleg Duke (Heaven is home...I am just TDY here!)
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To: Joe 6-pack

You owe me a new keyboard!


73 posted on 02/25/2007 6:12:39 PM PST by Redleg Duke (Heaven is home...I am just TDY here!)
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To: DBrow

Yes but you are hungry again in 30 minutes.


74 posted on 02/25/2007 6:16:38 PM PST by mad_as_he$$ (So many geeks, so few circuses.)
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To: Redleg Duke

Wow, who resurrected this year old thread?


75 posted on 02/26/2007 4:07:14 AM PST by caver (Yes, I did crawl out of a hole in the ground.)
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