Bluegill

A dark blue or black "ear" on an extension of the gill cover called the opercular flap; a prominent dark blotch at the base of the dorsal fin, close to the tail; typically olive-green backs, with a blue or purplish sheen along the sides; faint vertical bars may be present along the sides; breeding males may have more blue and orange coloration on their flanks (Ref. 44091).