Just like the salmon brought into the Great Lakes to take on the alewives. Which were brought in to take on the zebra muscles[0]. Which came in [bilges from ships?].
I remember visiting the Lake Michigan dunes in Indiana in the 70s, only to encounter what appeared to the small me to be mountains of dead alewife. Ten years later, my grandfather took me salmon fishing there. I'd imagine that by now, the ecosystems of the Great Lakes bear little resemblance to what they contained 200 years ago. Sad in a way, but the whole of Earth seems destined to becoming a single, climate-based ecosystem. Island ecologies may survive for a few centuries, but the main continents are going to become very consistent, with all the world-champion species holding sway.
