The Northern Squawfish
The champion fish-eater in North America is the squawfish, found in the Pacific Northwest. It can actually eat fish larger than itself. Think about it, a squawfish can digest a fish as quick as it is swallowing it. Since one of their favorite meals is salmon, there have actually been bounties placed on the squawfish. As a general rule, a piscivorous (fish-eating) fish like a bass can eat another fish that is cylindrically shaped, like a shiner, that is up to 1/2 it's own length and a flattened fish, like a bluegill, that is up to 1/3 it's own length. In other words, a 12 inch bass weighing about a pound can eat a 6 inch shiner or a 4 inch bluegill. Large bass can starve if the only forage available is too small, because they expend more energy catching and digesting a small fish than the energy they get from it.
You may want to keep this in mind and use large baits if you're fishing for trophy bass. A man in Alabama who used 14 inch plastic worms when fishing for bass. He didn't catch many fish, but you should have seen the fish mounted on his office wall. Also, if you're looking to catch a bass worthy of your wall, look for bodies of water with large bream. If a pond is limited to only small forage fish, the size of the bass at the top of the food chain will be limited, as well.