TJ,
The turbidity itself may have greatly limited the SMB's ability to effectively prey on the crayfish. Also, even if not gape limited, there is probably a ratio of cray length to SMB length that will serve to limit predation. A 5 inch Northern (rostrum to tail length) weighs in at .20 lbs. Takes a pretty good fish to tackle it.
To be sure, the best for controlling crayfish will be CC. I think it wouldn't take a lot of them if they were a good size. Probably 40 to 50 lbs/acre of 3 lb+ CC would be able to keep them under control. With no fish the Crays are probably limited to 800 lbs/acre. With fish it is much less provided the fish in the pond are eating them.
I would just add one more thing. Where one is adding crayfish as forage ... I would not do this in advance of predators. They are very prolific and they grow fast so they will offer no food for fingerling predators when they are introduced. They will also greatly impact lepomis reproduction. I would think a good time to add crays would be after the predators have attained a size of >16" or so.
