I'm at work and don't have the link that's saved at home, but fish population studies going back to the 70's documented "very few" sealions more than 10 miles inland. 10 miles is a pretty normal range for pinnipeds in lower river estuaries, but 156 miles upriver, is not. there are THOUSANDS in the river above that ten miles up to bonneville and then they figured out it's a similar shirt show at willamette falls, and have cashed in there too.
Until the manmade obstacle is removed, man needs to control the problem. 6 is nothing. it will not impact the population. It's a step I guess, but compared to how many are up there it's just a sliver.
I love the bleeding heart liberals that don't know anything about any of the population studies that have been done, or the that there have been many relocation attempts, that all comment about how fishermen are the a-holes and the state needs to relocate them blah blah blah....gah, I wish people would read before they start typing, or open their mouths.