We can't go back to the way things were, but there's a thing in toxicology called the dose-response relationship. Essentially, if I expose an organism to a certain dose of chemical, what's the response going to be with the chemical? We can do the same thing in invasion biology. If I have 10 propagules coming in on a ship, I don't know what the exact risk is of 10 propagules, but I do know that it's a lot lower than if there were a thousand or a million propagules. It might be a linear relationship that the more you add to a system, the more we inoculate the system, the greater the risk that some of those species are going to survive.
What we want to do is drive the number of organisms in these vectors, in this case in ballast water, down so low that even though the species may be introduced to Canada, they're not introduced at a sufficient abundance that the species can survive and establish here.
My colleague a couple of weeks ago, Ladd Johnson referred to a thing called the Allee effect. Essentially what happens there is that if the organism abundance that gets introduced is small enough, they can't find mates. And if you can't find mates, then you may survive but you're never going to reproduce and therefore.... We have an organism, I'll give you an example, called the Chinese mitten crab. The Chinese mitten crab has these big claws that look like mittens. It lives primarily in rivers but during the adult stage, lives out in the sea; sorry, they reproduce in the sea and they live in the rivers. We have caught these crabs in Lake Erie on a number of occasions, great big mature crabs, very large individuals. They don't pose an invasion risk to the Great Lakes because they can't reproduce in fresh water. They must go out to the sea to reproduce, so they pose no invasion risk.
What we want to do with all of our vectors, or certainly with the major vectors, is we want to emasculate them, if you will. We want to reduce the number of individuals that they're carrying to the point where they're no longer risky.
I may be wrong, but I think we're at that stage with ballast water. I haven't talked about hull fouling, but I think it's a huge issue for Canada.