Looks like there are several things going on, and all are interelated. The best way to address this is to have someone evaluate the fish population, water chemistry and vegetation/structure. Harvest data sometimes is a good indicator for a population, and sometimes it is not. I managed a 25 acre public lake in North Florida that had the best bass and bream population in the state, as indicated by electrofishing results. However, creel data showed something totally different. Low angling succes rates can be from high angling pressure and educated fish, habitat not allowing anglers to access where fish are or angler skills being less than average. Does not sound like these apply. but, a combination of harvest data and electrofishing are generally needed to really asses a fishery.
Crappie are cyclic, and are hard to manage in water bodies below 15 or 20 acres, and I don't like to see them unless the lake is greater than 25 acres. They are probably competing for and supplying forage at the same time. Certain catfish species can consume a lot of forage fish once they reach certain sizes. Usually not bullheads, but the worst is flatheads, they eat constantly. Channels are in the middle, until they reach 5+ lbs, then they will target all fish they can swallow, but don't eat all the time like a flathead. Channels and flatheads will also still eat fish food when they get big.
From this thread removing about 25 or more LMB's per acre, the first year, between 12 and 15 inches, and removing all crappie above 8 inches (best eating fish in the lake anyway) should be done first, if you do not get a lake evaluation. Fter year one see how bass are growing and modify the harvest rate accordingly. Then the addition of some forage that will naturally reproduce with proper habitat present is next. Sounds like there is habitat for forage survival, but you may want to encourage some desirable vegetation growth along some shorelines. Cypress in water do house some invertibrates, but not like quality vegetation stands.
Good luck!
