Green Crabs

The Shore Crab or European Green Crab (Carcinus maenas)

The green crab (Carcinus maenas) is a tiny brownish green crab native to the European shore line along the north-east Atlantic Ocean and the Baltic Sea.  Although it measures only 90 millimetres (3.5 in) across, it is voracious omnivore which feeds on all sorts of small mollusks, tiny arthropods, and worms (not to mention whatever dead flesh it happens across).  Green crabs are great and all, but this blog is not about crustaceans…Why is this little crab showing up here?

A green crab eating a clam

It turns out that the green crab is one of the most invasive species of our time.  Like the fiendish zebra mussel, the green crab is capable of traveling by boat (either among barnacles or in ballast).  As far back as the age of discovery they were hitching rides around the world on the hulls of wooden ships.  The little crabs seem to have piggy backed into temperate climes along with the British Empire and they have set up ranges in Australia, South Africa, Argentina, and both coasts of North America.  So far this has not been a big problem: for hundreds of years, cold waters and big hungry fish have kept the little crabs from proliferating.  However as humankind moves forward with its dastardly plans to kill off every fish in the ocean (and as ocean temperatures rise) the crabs are beginning to flourish in places where they were once barely holding on by their claws.

Green Crabs Spreading through the World’s Oceans…Yikes!

Green crabs eat clams and juvenile oysters—so their success is causing hardship for mollusk fishers (while simultaneously removing filter feeders from the ocean).  Along the Mid Atlantic coast of North America, the native blue crab has proven effective at out-competing (or just straight-up eating) the invasive green crabs.  Similarly the rock crabs and Dungeness crabs of the Pacific northwest can hold their own against the invaders, but humans are overfishing these native crabs and allowing the invaders to proliferate (and seafood enthusiasts in America have not developed a taste for the tiny green crabs).

Not exactly a whole seafood platter…

Will the warming of the oceans cause blue crabs to spread northward to defeat the invaders?  Will humankind stop killing every fish in the ocean so that the green crabs are eaten by sea bass?   Will we introduce a new species which preys on the green crabs (but brings its own problems)?  Only time will tell, but already coastal Maine is being swept by a tide of little green claws (and delicious east coast oysters are becoming more expensive and more rare).

“Dead or Alive”, people…

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