Happens more often than you think. I've found several 10+ bass over the years with big (3/4 to 1 lb) bluegill stuck in their throats. Especially in the spring when the females are guarding nests. If the bluegill gets turned sideways with his dorsal fins up and the bass can't get it turned head first, if he's big enough, he'll wedge in there and the bass will not be able to close its mouth and basically drowns pretty quickly. I've got a pic somewhere of a huge bluegill (still alive) that I pulled out of the mouth of an 11 lb bass on Lake Juniper one spring. I saw the bass laying on the bottom about 30 ft from the bed I had seen her on the afternoon before and netted it up. It was fresh, and the bass still had good color, like it had just happened. Ran water through the bass's gills for a couple minutes and tried to revive it but it was gone. Bluegill was still alive and swam off after I finally got it unlodged from the bass's throat. Never seen it happen with a shad though.