Yes. Fraser River sockeye is a good example of that. Once every four years, there is a very large return. That's been consistently large, once every four years, since the 1940s or thereabouts, after the Hell's Gate fishway went in. That's been consistently strong in the order of approximately five million to 30 million salmon coming back.
Those juvenile salmon go out to sea, en masse, and the analyses suggest that there are so many salmon and so relatively few predators per prey item—like the seal population, for example—that they just get swamped. They can't actually have as big of an impact on those migrating sockeye salmon. As well, the Steller's sea lion population—the adults—would get swamped in terms of the short time they come by.
The much smaller populations of sockeye salmon, between those dominant years—the three subdominant lines—were actually quite abundant, up until the 1980s. Then we saw subsequent declines, and those off-cycle lines have been decreasing progressively. The abundance of Steller's sea lions, for example, is high enough, such that when there are only a couple of million salmon coming back, they could easily eat 6% of them. That's what our study has suggested.
What happens is that you get a much lower stable equilibrium. Even with no fishing at all, you might get 10 million salmon coming back, but with seals and sea lions, it's like another fleet. It's holding those sockeye salmon at a very low level, maybe one to two million; we don't know. Those trends are worrying because they're going down and down. It could be either a stable or an unstable equilibrium, such that it's maybe stable at a low level, or unstable and maybe going to extinction. We can't distinguish at this point.