I would say the 18 lber is probably a small 3 yr old and the 12 lber is a second year fish. My observation is there are more 2 yr old fish that are maturing every year, especially over the last 10 yrs. Many of these years there was no problem with the bait fish population but I've caught and seen more fish maturing in their second year based on the size of the fish relative to the size of all the rest of the mature fish I was catching in the same areas on the same day. I fish in the area of the Salmon River.