Looks GSF to my eye as well. Immature GSFcan have the red eye mark, especially when eating lost of crustaceans like amphipods or isopods. Fins also get a reddish orange tint. Adults more than 3" loose the reds.


Note the short spines and rays on the dorsal fin when compared to other sunfishes like RES, BG and Longear Sunfish likely to be found in your area. Mouth size is not all that reliable as that may vary as a function of diet.


Aquaculture
Cooperative Research / Extension
Lincoln University of Missouri