Back in 2009 a fisheries biologist here in California found this freshly dead salmon in the Sacramento River up by Colusa.
It's a monster.
The link to the article on this is dead now, but it illustrates the shocking size some of the local fish grow to.
A guy I work with showed me a photo of a big rainbow trout he'd caught in the same Sacramento River right in Redding, and it was huge, brightly colored and frankly so beautiful I would have been tempted to put it back - stopped only by the thought of the tasty fillets it would give and the fish bake that would come later.
According to him, the salmon use their tails to wash out breeding redds right there on the gravel bars, and the big rainbows living in the river collect to eat the bugs and the roe that this activity stir up and wash downstream.