No. At this point, we have hypotheses. Obviously, there's global warming. It's not just global warming; abnormal cooling can also be problematic. As you mentioned, there's also predation, which can be a significant factor. Disease is another factor.
Could there be factors we're not aware of? Could changing river conditions mean that smolts completing their migration are less healthy than they used to be? We're currently focusing a lot of our work on this. We have these four hypotheses, but we don't have any answers. We need to keep looking for those answers.