I wasn't trying to say there is a gap in the size of fish if that is how you took it. Normally when I go, I catch fish of various sizes from 10” through 15” and above. This leads me to believe there is normally a good spawn every year and jet props aren't hurting the population.
Of course the bigger fish are harder to catch so I don’t normally catch as many of them. I consider a smallmouth over 15” a decent fish and anything over 18” is a trophy. But they are definitely plenty of 18” fish in the Meramec and I have the pictures to prove it.
Last time I went, a couple weeks ago, I had caught a few. Then went a while with nothing, Then caught 4 smallies on about six cast and they were all between 14”-16”. All were taken on a big white spinner bait with a white curly tail trailer. And they all came from an area with deeper water and boulders. And there is also a decent creek that comes in right above the deeper water.
Hope that helps.