Ryan -- one other possibility. There's been at least some thought that there are two body forms for bluegills. One is the saucer shape, and the other is more streamlined. If a bluegill lives in submergent vegetation, the saucer shape would be better for avoiding predators (fast turns) and feeding. If a bluegill lives in an open-water environment, then the longer body shape might be better for predator avoidance (faster).
Actually, that speculation is the easy part. Now, the hard part: is it genetics, or is it an adaptation to the environment (meaning that all bluegills have the capability to go "either way" depending on the habitat in which they live)? I have not seen an answer to that one.
This should start some discussion, eh???
