Friday July 12, 2013 | 11:17 AM
Posted by Harold Johnson

Visiting a cobbly shore on a warm, misty summer morning, it’s fun turning over rocks. I did yesterday, to see what was lurking on the cool, wet undersides. Time after time after time, I found one thing:

and

and

and

The European green crab. One or two of these were under most substantial cobbles that overturned yesterday.

Worryingly, I found nothing else at all.

The European green crab lived happily isolated in the northeast Atlantic and Baltic for millennia. Then, somehow, in the early 19th Century it was introduced to American shorelines. Since then, it’s spread to both coasts of the US, as well as five continents.

The green crab is a voracious predator, eating everything from algae to fish, snails, clams, you name it. It’s also an exceptional breeder. 1 female can produce 185,000 eggs with one clutch -- and can produce multiple clutches in a year.

This link (to a PDF file) will give you everything you wanted to know about the European green crab, and more!

Because it loves bivalves like clams, oysters, mussels, and scallops, the green crab has devastated many of the shellfish fisheries of the world.

Up til recently, Maine had been spared from the worst of this threat, largely because our winters were too cold for the crabs. But the Gulf of Maine is heating up, like the rest of the world’s oceans. Since about 2007 the green crab has been thriving here.

As the Press Herald reported in March, the president of the Maine Clammers Association said, “We’re in big trouble... Green crabs have already eaten their way through the scallops, urchins, mussels and now clams.”

And when the clams are gone, what’s next? Lobsters. The crab is already being found in deeper and deeper waters, following the lobsters down to their territory.

Maine’s ocean fisheries brought half a billion dollars of revenue in 2012. But a changing climate, and changing seas, are picking off marine species one by one.

And I got to see part of that playing out on my deserted, protected beach just yesterday.

It’s one thing to read about a threat that seems nebulous and distant. It’s something else entirely to walk the beach and see it right under your feet.

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About the Author

Visiting a Maine beach in March 2010, Harold Johnson was shocked by the ocean-borne debris left by recent storms. He grabbed a garbage bag and a camera, and hasn’t looked back.

Since then he has spent most of his free time studying marine pollution, coastal ecosystems, and the mysteries and science of ocean and shore.

Copyeditor and writer by trade, historian and archaeologist at heart, Johnson’s philosophy is simple: Dig below the surface, travel the currents, make the connections, learn. Then share what you learn. He lives in Saco with his wife and young daughter. Follow on Twitter @FlotsamDiaries.

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