Depends on what crabs we're talking about. Are they big blue claws like you'd see in the restaurant, or are they small, only a couple inches across? Blue claws are eaten but you shouldn't eat them from the river. If they're the latter, they're invasive European green crabs, and a very popular bait for blackfish.

There are some people in New England trying to develop a culinary fishery for them, but it involves catching them, waiting for them to shed, and then eating them as soft shell crabs.