Why do people build perfect habitat for wildlife and then get upset when they show up? Snapping turtles do eat fish but they can't catch as many as people think they can. They also eat crayfish which can undermine your dams, they prey on muskrats which will truly destroy a dam. And the fun thing about predators, they don't overpopulate unless there is an overabundance of prey. What about the herons? They eat fish, should they be killed as well? If it is really bothering you, catch it and put it someplace farther away. We only kill animals which are directly impacting things that we are needing to live ourselves, squash bugs, bean beetles, etc. Raccoons that get after the chickens. Even the bears are "educated" to leave us alone. I have always believed that one of the goals of permaculture is not to change the world to make it perfect just for humans, but to improve it in total and leave some room for the wildlife.