The truth of the matter is that the smaller fish do most of the reproduction...
I'm glad you said this so I didn't have to. (I think it would have looked like I was reaching for excuses to back what I said when that wasn't the issue I was trying to focus on).
In 1993, I attended a smallmouth and walleye seminar put on by Wisconsin DNR biologists. Talking about walleyes, they said no one should feel bad about keeping a trophy fish; and that the spawning success rate for walleyes drops off markedly after 6 pounds, to where 10 pounders have (essentially) zero success in spawning. (They said it was because trophy fish are not as healthy as the younger ones and the big fish produce more eggs per body weight with substantially less quality per egg.) Granted this came from the DNR, and they are part of the government, but I believe what they said was legit... I'm not sure if this can be validated on line, but I'll forever remember some of those stats from that seminar.