If I was eating fish I would keep anything over 12 inches. Research shows the best crappie spawners are from 8-10 inches. Many over your bigger fish will die anyway during the spawn, especially with the added stress of being caught. Remember crappie lay between 17,000 to 21,000 eggs at the time. Their largest predators are other crappie and bluegill. By the way the males protect the eggs so what about the times when you pull a limit of males off the bed? What happens to those eggs?