That question is frequently asked, and no scientist can answer it. There is no ideal level. There is in ecology no balance of nature. That was rejected by ecologists about 70 years ago. So this is one of these things that kind of carries on. We can see it today; you just have to look at the Arctic and what's happening to polar bears. There is no balance. The world is in constant flux, sometimes because that's what the earth does and sometimes because of our activities.
If there were no seal hunt tomorrow, what we know about the biology of seals is that they would in fact eventually limit their numbers through the availability of food and competition between individuals. Technically, it's called a density-dependent response. We would never predict that a seal population would simply explode.
There's just one more brief point. I would like to refer to density dependent. What it basically means is that as the population goes up, individuals have to compete more for food, they get less food, their birth rate does down, their mortality rate goes up, etc.
In response to a question earlier and to your question, I'd like to refer you to a paper that was recently published, co-authored by a person at UBC and by two Canadian government scientists in Mont-Joli. It's called “The Trophic Role of Marine Mammals in the Northern Gulf of St. Lawrence”, and it talks about the role that marine mammals play in marine ecosystems. The last line talks about--this is the last line in the paper—“This beneficial predation effect is even greater than the predation itself, leading to an overall positive impact of the predator on the system.”
In other words, this complex system, which I did show and I actually referred to in this year's presentation, is structured and ordered by the feeding interactions that occur in it, and harp seals eat all sorts of prey, as you noted in that figure. The end result is a positive impact on the system. If you start to remove predators, it reminds me of what Victor B. Scheffer, one of the grand old fathers of American pinniped biology, said in 1972: “If you remove seals from the system, what sorts of holes are left?” We can't answer that question.
Thank you.