Remember that live trade includes lots of sub-vectors. We're talking about moving species for commercial purposes. We're talking about aquarium dumping after the aquarium industry has distributed species. There is bait-bucket dumping. After the bait trade has distributed species, people on the ground will start dumping them. That's how rusty crayfish and a variety of other things have been moved around and continue to be moved around.
Ultimately, human behaviour at the small scale will continue to distribute things after the larger-scale operations of industries have introduced them to a region.