You so can't blame this on global warming... I would say it has more to do with the sedentary lifestyle of said salmon and their unwillingness to breed...
That and the fact that there are too many fishing boats out there overfishing for these babies..
Though to me anyway, what Ferre says is correct (yes dude, you did hear me correctly, I am actually agreeing with you
) and there is more damage that can be proven being done elsewhere and though global warming is a fact, the harder part to prove is just how much damage man is actually contributing towards this.