Pre-Colonization Seals and Sea Lions did forage pretty far upriver in the Columbia right? I found
this paper that says they were common all the way to Celilo Falls where they gathered in large concentrations. I would assume that the federal/state regulator's justification for not just doing lethal removal is that this isn't a new behavior spurred by the dam placement they are just resuming what they were doing before. Is there any possibility that the seals carrying capacity will be limited by something other than food like competition for space, disease, etc. and the population at Bonneville will max out? Like I'm imagining if managers could just go okay Bonneville dam/lower Columbia River as a whole supports around x number of seals which take around x number of fish, then factor that into broader calculations for allowable take, just like every other natural factor that affects salmon populations and is factored into fisheries forecasts. That seems a lot less silly than just killing/removing them when there are always going to be more to replace the ones we take away. Especially since this doesn't seem like a very uncommon behavior where we could just get rid of the bad apples and be good for a while, given that seals forage pretty far upriver on most coastal streams with a salmon presence.