Knowing what lives in your area is the first step to protecting it. The brook trout, which is the only native trout in the Great Smoky Mountains, once swam abundantly in southern Appalachian streams. Over the past century, however, local people have observed that this native fish is vanishing. Scientific monitoring and studies show that rising water temperatures, acid rain, competition with non-native fish, and over-fishing have scaled back native brook trout populations. Fortunately, identifying causes to problems leads to solving them.