My thanks to Alan Miller on the Texas Fly Report website for digging through all the mulititude of internet resources to find this information. And my thanks for allowing to repost it here.
Well I've been fishing these buggers for quite some time. I've seen and heard them called by many names. So hopefully this little tidbit well help some of you out.... Sunfish (aka bream, perch, bait)..... Why is it so hard to tell these fish apart?? The Sunfish family includes some 30 species, and is found only in North America. This family includes the Black Bass and Crappie. This family is one of the most popular and widely known gamefish groups in North America. Anglers like Sunfish because of their fierce tenacity when caught by hook-and-line, and their firm, white flesh. Different types of Sunfish often crossbreed, resulting in hybrids that have some characteristics of both parents. Hybrids may even crossbreed with other hybrids or with their parents. Even experienced biologists have trouble identifying fish from a hybridized population. Small hybrid sunfish are a nuisance in many lakes, but some hybrids are often superior to the parent fish. For example, Redear Sunfish, when crossed with Green Sunfish, produce a fast-growing, hardfighting hybrid.
Here are some of the most common:
live colored with brassy reflections and dark mottlings along the sides, each side scale contains a dark spot. Anal fin with 5—6 sharp, bony spines; dorsal fin with eleven spines. Large mouth. Stiff gill cover with very small ear spot. Maximum known length is 17 inches with a weight about two pounds. Rarely attains that size, average adult is about 7 inches.
Bluish green back and sides with white to light yellow belly; sides of the head mottled with emerald and yellow streaks; black ear flap has a whitish or yellowish margin; leading edges of the dorsal, anal and caudal fins typically whitish or yellow-orange. The largest example of this fish from Kansas weighed 2.33 lbs and had a length of 11.5 inches.
Thick bodied with olive-brown color on back and sides. Sides covered with dark mottlings, belly yellow; 4 to 5 red/brown streaks from the red eye, closed mouth extends to eye.
Bluegill may be distinguished from other Sunfish by the dark spot at the base of the dorsal fin, vertical bars on their sides, and a relatively small mouth. The spiny dorsal fin usually has 10 spines (but may have as many as 11 or as few as 9), and is broadly connected to the soft dorsal. The anal fin has three spines. The back and upper sides are usually dark olive green blending to lavender, brown, copper, or orange on the sides, and reddish-orange or yellow on the belly. Colors are more intense in breeding males, and vertical bars may take on a reddish hue.
Color blue-green with amber fins and belly. Crest of back with amber stripe. “Ear” flap very long in adults, with thin white edge. This flap, always trimmed in white in adults, is unique and makes field identification relatively easy if hybridization has not occurred. Mouth small. Pectoral fins short and rounded.
Color pale, silvery or with faint brownish mottling. Red crescent at edge of dark ear-spot. Small mouth. Long pectoral fin with sharp point. Most resembles Bluegill.
Large mouth that extends to front of eye when closed; spiny dorsal fin with 10 spines, directly connected to soft part of fin; long gill flap with vivid orange spots on the side. Breeding male with sides of head blue streaked with orange, breast and fins orange. “Ear” flap long and flexible with rounded black spot and broad white margin. Grows to 6 inches.
The Smallmouth Bass is generally brownish/green with dark vertical bands rather than a horizontal band along the side. There are 13-15 soft rays in the dorsal fin, and the upper jaw never extends beyond the eye. Scales on cheek and gill cover very small and granular, scarcely visible. The Smallmouth Bass can attain weights of 6 to 8 pounds, but rarely weighs more than 2 to 3 pounds.
Body is green-shaded with a broad, continuous dark stripe along each side; belly white to yellowish; dorsal fin almost completely separated between spiny and soft portion and lower jaw extends past the gold-colored eye; commonly reach lengths up to 16 inches by three years of age.
Spotted bass have dark spots on the gill cover and spots or streaks on the lower sides of the body. The upper jaw does not extend beyond the back of the eye when the jaw is closed. Spotted bass have a patch of teeth on their tongue, whereas very few largemouth bass have tooth patches.
Anal fin about as large as dorsal fin; both of these fins with 5 or 6 stiff spines. Color plain white or silvery, usually with faint vertical bars. Males dark, head and breast nearly black, in spring and early summer. Resembles Black Crappie, but body less rounded, never irregularly spotted with black, and rarely with more than six dorsal spines.
Anal fin with six spines and nearly as large as dorsal fin. Dorsal fin with 7—8 spines. Body irregularly flecked by dark spots, never banded. Breeding males with head and breast black. Resembles White Crappie.