The easiest way to tell the perch from the white bass is to lift the front dorsal fin. If the back one comes up with it you have a perch, otherwise it is a white bass. Had a marine biologist tell me that after numerous attempts to tell them apart. There are other differences but this is the easiest way to determine.
Here is a link http://www.identicards.com/allaboutf...asp?fish=white perch
It states in this link that the dorsal fin is not separated which is why both parts come up if you lift one, not so the white bass,