There is a season I think, look it up
Timothy Lake is full of them, 20-30 feet, better at night.
Lake billy Chinook is a safe bet, more like 35 feet there. I have had traps full to the brim there.
I have heard Ollallie, Lost and Promitory lakes can be good, I have never fished them.
Diamond lake used to be good also.
I wouldn't eat any from the Columbia, lower Clack, Tualitin or Willamette rivers.