If the entangling lines are recovered from the whale when it's either disentangled or during the necropsy on the beach, if there are sufficient identifying characteristics on the gear.... The gear is measured, and the diameter of the rope, and if there are any buoys present and there are any licence numbers on the buoys, every effort is taken to try to track that gear back to the fishery, certainly not for blame but to try to figure out the problem.
In some cases, it's just a length of rope and it's not possible, but the rope that has been collected has been both of Canadian and U.S. origin from a number of different fisheries.