Wow, good one, guys! They look so different when they're young, huh? Those big eyes... awww. I have worked with juveniles of the sunfish family (Centrarchidae: Sacramento perch), and they do look a lot like that. It certainly has the spines in the leading part of the dorsal fin. Sometimes even professional ichthyologists have a hard time ID'ing juves, and have to do spine counts. They're quite differently proportioned from mum and dad. I guess the universal baby thing: large head, big eyes, cute face, don't eat me!
Good call, greensunfish, for getting that one. You've lived up to your username