It could be as simple as years and years of outdated regulations on bluegill, i.e. a creel limit that's about twenty fish higher than it should be, catching up with the lake. Said regulations certainly did a number on the bluegill fishing at Shellcracker Lake in Williamsport. That lake would have one of the best trophy-bluegill fisheries around now if better regulations had been put in place four years ago, when it started getting a population of big ones. I suggested a five-fish limit, along with a slot limit of 8-9", to the region head for TWRA, but he said they would have to do an angler survey to see if anyone was fishing for bluegill, and two months later the big ones had been fished out.