A black bluegill?

Can you guess why this bluegill is so dark? Do you think it is because the pond from which it came had muddy water?

I caught this bluegill and several others June 12 in clear water. Only this 9-incher and one other the same size were black. Both were males. This is spawning season for bluegill. In farm ponds, a male bluegill will scoop out a nest the size of a dinner plate near the shoreline. After the female bluegill deposits thousands of eggs in the nest, the male guards the nest. Several days in shallow clear water guarding its nest allowed the sun to shine on this fish, causing its scales to become darker and darker.

In muddy water bluegill scales become lighter in color.