I play in streams a lot in the southern half of Missouri. Northern Bluegill are in most streams with permanent flow. Size / age structure in most of the lower order Ozark streams appear odd. Most of the bluegill range 3" to maybe 5". Within that size range the smaller end is much more abundant. Even the smallest are large enough to breed although I do not see them nesting in areas I visit. Longear and Green Sunfish are easy to find nesting and it is easy to find even fry in the same reaches. The bluegill I think are breeding down stream then then move upstream as juveniles until big enough to compete in breeding colonies, then they move back down into the larger streams with more substantial pools. If correct, there is a lot of moving about.
This rushed to will revisit later.