From jcenter.com

   More than five species of non-native crabs have invaded the US in the last fifteen years. Most of them reproduce quickly and often prey on shellfish causing alarm among researchers. Studies conducted in nine coastal reserves will monitor native and invasive crab species and attempt to document their reproduction rate, and spread. Particular attention is given to the Indo-Pacific crab, that feeds on soft shell clams and oysters and Asian shore crabs, who feed on juvenile oysters. All predatory nonnative crabs could be disastrous to the fragile ecosystem that supports the shellfish industry. To assist the public in helping researchers track the crab's spread, the project will disperse glossy identification cards.