How did the Round Goby reach North America?

there are 2 theories. some people think they came in ballast water tanks but some people think that it was brought here on purpose because the Round Goby eats the Zebra Mussel(another invasive specie) and the Zebra mussel was in the Great Lakes first so people think that someone brought them here to take care of the zebra mussel invasion but as it turns out, the Round Goby became invasive as well and sorta helped the "zebra mussel invasion".