July 22 – Feeling Crabby

Today’s factismal: Live mitten crabs are sold by vending machines in Chinese subways.

The mitten crab is an ugly critter. They get their name from the hairs that cover their claws, making it look as if they are wearing mittens, but that isn’t their worst feature. They have four sharp spines on their bodies, but that isn’t their worst feature, either. They have sharp, pointy legs for walking on the bottom (they don’t swim), but that still isn’t their worst feature. What is their worst feature? That they are invading Europe and North America.

A mitten crab (Image courtesy Mitten Crab Watch)

A mitten crab
(Image courtesy Mitten Crab Watch)

These crabs are native to Asia, where they are a popular delicacy. Mitten crabs are so popular there that they are sold through vending machines and are seen on many restaurant menus; the crabs from some areas can fetch upwards of $50 per pound. They are traditionally served with ginger and vinegar, and are eaten through the latter part of the year. More than 200,000 tons of mitten crab worth more than $1.2 billion are eaten every year in China. Indeed, mitten crabs may be too popular in China; they are now a rare sight in many parts of their traditional range.

A mitten crab (Image courtesy Mitten Crab Watch)

A mitten crab
(Image courtesy Mitten Crab Watch)

Unfortunately, they are becoming an all too common sight on the coasts of North America where they were introduced by freighters discharging their ballast water. First spotted in San Francisco bay in 1922, they now are found as far north as Portland and as far south as San Diego; they have also been spotted in Boston and Baltimore on the East coast. Mitten crabs eat fish roe and the larvae of other crabs, reducing native species; they also burrow into the banks of estuaries, causing local collapse and damaging dams and flood control projects. Some estimate their annual damage at more than $80 million.

Fortunately, there is a simple solution to the mitten crab invasion: eat them! In California, you are allowed to catch up to 35 mitten crabs each day; similar rules apply in Oregon and Maryland. But, before you dig out the butter and Old Bay, be sure to take a picture of the critter and send it to the researchers at Mitten Crab Watch. They are trying to track the mitten crab so that we can discover other ways to control the invaders. (You might also use the website as a way to find the best places to go crabbing.)
http://mittencrab.nisbase.org/

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