Here is "official" key to identifying different sunfishes from TWRA Biologists.
However, in many cases it is difficult to follow the key without the fish in hand.
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Lepomis are members of the sunfish family separated from crappie and rockbass in that they have only three spines on their anal fin. They are separated from their other cousins, the black basses (largemouth, smallmouth, and spotted), by body shape.
Use the following key to help distinguish between the seven species of Lepomis found in east Tennessee. It has been derived from The Fishes of Tennessee by David Etnier and Wayne Starnes and with help from Rick Bivens.
We receive many calls from anglers that believe they have caught a state record pumpkinseed, but all recent reports were misidentified sunfish from outside the pumpkinseed's home range. They have only been documented in the northeast corner of the state in the general area of South Holston and Boone Reservoirs.
Note that color varies significantly within species and is not a very reliable characteristic. Also, natural hybrids of sunfish are very common which makes their identification even more troublesome.
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1. Pectoral fins long and pointed, extending to or beyond the anterior rim of the eye when bent forward - go to 2.
Pectoral fins shorter and tips rounded - go to 4.
2. Dark spot on the back portion of the dorsal fin; body with vertical bars - bluegill
No dark spot and body without bars - go to 3.
3. Pectoral fins very long and extending to or beyond the dorsal fin base - redear (shellcracker)
Pectoral fins shorter not extending to the dorsal fin - pumpkinseed
4. Tongue with a tooth patch - warmouth
No tooth patch - go to 5.
5. Lateral line scales 43-50; relatively large mouth, jaw extending to or well beyond front rim of eye- go to 6.
Lateral line scales 32-43; small mouth; white margin on the opercular lobe - longear
6. Large mouth; body "bass-like"; dark spot on the back portion of the dorsal fin; opercular lobe bony and inflexible - green sunfish
Mouth smaller, deeper body, no dark spot on dorsal fin; opercular lobe fleshy - redbreast
Pictures on this page:
http://www.tnfish.org/FishIdentificatio ... on_Key.htm