Everywhere you go in California, people live in landscapes where non-native species are conspicuous:  European grasses turning the hills golden, earthworms tilling our garden soil, exotic trees providing shade, bullfrogs jumping into backyard ponds, starlings making tight maneuvers overhead. In this blog, I want to describe the language of our relationships with non-natives and the nature of those relationships as biological phenomena, using fishes and other aquatic organisms as examples.