Green crab (Carcinus maenas)

Carcinus maenas better know by its common name green crab is originally native to Europe and is now dispersed globally with records of occurrence in Australia, Hawaii, Sri Lanka, South Africa, along the Atlantic and Pacific coasts of North America, and the Atlantic coast of South America

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 It was first introduced into the U.S in 1817 by ship's ballast water  and is now the most abundant crab species with the females being able to produce up to 185,000 eggs per sponge.Green crabs eat a wide variety of prey organisms and can significantly reduce populations of native clams and crabs in areas where they have become established. Their ability to out compete native species for food resources, high reproductive capacity, and wide environmental tolerances lend them the capacity to fundamentally alter community structure in coastal ecosystems. Their main prey ranges from clams, mussels, oysters and gastropods. 

The economic cost of these invasive species are very high as they reduce the native species populations and reduce income of fisher men who depend on the ocean to live.