Of course in most places, “non-native” fish are considered a problem, and everything is done to prevent their living and spreading. And yet, I’m guessing that if you go back far enough, the majority of fish anywhere are “non-native”.
I used to explore the Rockies - met folks that continued their grandfather’s role of taking trout fingerlings in milk containers via mule to seed the various high mountain lakes and creeks.
Plus all of the natural “non-native” fish that have coursed through the rivers and creeks lower down over the last 12,000 years.
A buddy of mine has an hilarious story about them packing a canoe into the Trinity Alps on a camping trip. One of the guys was out in the middle of the lake fishing when up pops an airplane to stock the lake. Pretty good pilot as he scored a direct hit on the canoe. They all got a good laugh out of that cept the guy in the canoe.