Again, the way it's been explained to me is that you're able to have a series of ecological responses or barriers. They're much more flexible, so you can adjust. If you've built a physical barrier and there's a way around it, you end up having a canal being dug for other purposes, you end up having some transfers for other purposes.
Again, it's looking at one vector only, the physical vector. It doesn't deal with the transport of live Asian carp for nutritional value. It doesn't deal with many of the vectors, whereas if you end up having a series of bubbles, a series of meshes, a series of.... They've used water cannons. They've used a whole series of various ecological or biological deterrents.
They're looking at using pheromones as a biological means of reducing their fertility or controlling their reproduction. All of those are a little bit more amenable to adjustment when you're dealing with the problems, rather than putting up a big physical thing that may solve one of the vectors but not all of the vectors.