On the east coast of Northern America where did asian/green crabs come from?

Question

Explain please.

Answer 1

Ballast water from ships.   The cargo is stacked high above the water, so weight is needed down lower.   Water is pumped in from the ocean for that purpose.   Now balast water is supposed to be screened, taken in further from land and exchanged at sea, but it's too late to keep those buggers away now.

Answer 2

ballast water,however green crabs Atlantic side were introduced by England 150 years ago. I am a ex-comm.fisherman and used them for hand lining black fish,looked up their history.Asian crabs are smaller but breed at a much faster rate,they also are competing against the green crabs for food. Man kind is slowly altering everything,shame on us.

Answer 3

all large ships leak.

larva and eggs also leak in.

when they're pumped out, so are all the animals that came in with the water that leaked in.