Actually, Lewis and Clark documented sea lions as far as Celilo Falls.
They are natural and not new to the river system.
They make a great visible scapegoat. "oh look at the evil sea lions eating what they have been eating for a thousand years."
If you want the real fish killers look at the dams, pesticides, fertilizers.
DO you use electricty?
We are all guilty of the fish demise.
I too love to fish but the seals are a poor excuse for the decline of fish populations
I think our limited resources could go to better use.
Save a fish and turn off your lights