Trout fishing as we know it in the U.S. would simply not exist if there were no "non-native" fish or unnatural environments like beneath hydroelectric dams. There would be no fabled Madison or Missouri River rainbows, and no world record brown trout in Milwaukee harbor. In fact, there wouldn't be any brown trout anywhere in America. Native to Europe, they were introduced to this country in the 1870s. Just like carp. So why do we not use the word "invasive" in the context of trout?