I'm not taking anything away from your dad but his assumptions don't hold water at all. Take a look at the latest scientific literature and you'll see that the amount of predation by walleye and bass in the Columbia is miniscule. To make the point take a look at the John Day river. Even though it's a mid Columbia basin steelhead river it has one of the strongest runs of steelhead despite other rivers in the region struggling....despite having one of, if not, the highest concentration of smallmouth bass in the country. We float it every year and even my daughter who is only 6 years old has caught as many as 70 bass on a flyrod in a single day and she can't even cast more than 20' and uses nothing but topwater flies. I personally get so bored fishing that river that I don't even bother and I'd rather see my girl catch fish all day.
Why are the John Day steelhead doing so well when the water quality during the summer is atrocious, both in temp and flow? For one, it's the 4th longest free flowing river in the United States, no dams! Even with such substandard water quality for a large portion of the year and a huge population of bass, the steelhead are thriving. The steelhead are free to move to the upper most reaches of the river to spawn and hold during the summer heat when the lower river is 75+ degrees. They can move up river without obstructions...hmmm, amazing.
Like I said in another post, many different factors face salmon and steelhead throughout their range. Not all of those are detrimental in each region depending on other circumstances but there is one thing that is detrimental to any steelhead or salmon no matter where they swim....a dam, and that point CANNOT be argued, period.
It shouldn't be that hard to understand that any manmade obstacle put in the way of migrating fish, or any animal, is going to be detrimental. The USACE publicly stated when the dams were installed that this would end salmon migration....why are we even debating this other than politics and $$?