Ive never seen a sunfish in my life,lol just pictures,,, ok after exstensive googling and inclings, ive come up with a couple of names, also i took the liberty of borrowing your pics asking around, i have come up with a couple of names for you to google,hehe
But bearing in mind it looks very stressed,if you could get some pictures once its coloured up that may help some what, but for now,
Oreochromis niloticus baringoensis / Oreochromis niloticus niloticus
Leaning toward a Oreochromis spp very much so,