Nothing is happening that has "forced" seals to feed in the rivers. Ever seen how far they go up with the pinks sometimes? Plenty of fish everywhere, but they will still follow fish right up rivers. I remember seeing seals up rivers back in the late 70s and 80s too. They've been going up rivers for years and it's not always out of necessity. Some seals follow their food in, some do not. The problem arises when a pod of seals learns to go up a river or hang out in an estuary and ambush fish. If it's a single seal though, even if it ate two steelhead a day, is not likely to do as much damage as the drones of fishermen that frequent the vedder.
I agree that DFO needs to do something about it, but only because fish stocks are already beat down, not because it isn't what a seal is "supposed" to do. Localized culls vs. broader culls....who knows what would work best? They work in and exhibit pod specific behaviors, so maybe some pods are more prone to hang out and ambush than others. I'm not a biologist but would take an uneducated guess that if DFO culled the problem pods locally that it would provide enough respite for most of the salmon/steelies that would have been munched to move along undisturbed.
All that said, declaring that seals "belong" in the ocean and not in rivers (especially in bold red caps) is misinformed, and really at this stage in your life you should be asking more questions than providing shoot from the hip solutions!
For anyone that doesn't know, you can be fined up to half a million and go to jail for killing a seal. Probably worth considering....