Is There a Leech in the Great Lakes?

humans have introduced approximately 180 species to the Great Lakes since the 1800s. The zebra mussel and the quaga mussel are what they call, they're just little mollusks. They think they were attached to cargo ships and, you know, like fell off, reproduced, thrived. And they're a danger to basically all life in the Great Lakes because they're over consuming the algae and nutrients that are naturally there.