Salmo didn't say they don't eat salmonids. They are not likely to eat smolts because of temperature during outmigration. They do eat salmonids, and WDFW knows that from sampling but it is likely that the majority are resident trout or salmon juveniles reading in the lakes in summer. Also, lake Roosevelt is not anadromous waters (now). They are eating resident salmonids.

Temporal and spatial considerations are important. There was a recent paper on Smallie predation in the Snake. They do eat Chinook smolts there. But, if there are lots of Sandrollers, they prefer them. Understanding the whole ecosystem might help us manage better.