Why did this invasive species suddenly take over Maine's coastline?

This scary looking beastie is the European Green Crab. It's not native to Maine, but they started coming over attached to the hulls of wooden trading ships a hundred years ago. But it's only just in the last two years that there's been a massive spike in the crabs' population, devastating the local clam-fishers. » 12/03/13 5:31pm 12/03/13 5:31pm