The high lakes are stocked every other year, and I believe they are odd numbered years. Stocking usually takes place after the trails are open enough, for those not stocked by air, for volunteers to backpack in canisters of trout.
Call the Clackamas office and ask to speak with Jennell, if you're interested in volunteering. She can probably steer you to which lakes will be stocked by foot, horse, or air.