If I could add to what David was saying, it really is species-dependent. If we look at the Asian carp and what we're seeing in the United States and the Mississippi watershed, there is a lot of sound science telling us that basically anywhere between 80% and 90% of the biomass is Asian carp.
Some things can get in and get established, and it's about the degree of impact. You can have a lot of them, but it doesn't really impact the native ecosystem. If you get something like Asian carp and you see what's happening in the Mississippi delta, that's a different story.