Diagnosis:  The smallmouth bass is a somewhat compressed bass, dark olive or yellowish brown, without prominent markings on the sides or with vague dark vertical bars, stripes across the cheeks, a gently curved spinous dorsal fin broadly joined to the soft dorsal, usually more than 67 scales in the lateral line, and a moderate-sized mouth, and without a lateral band or rows of longitudinal stripes on the lower sides.

Ecology: It occurs in clear, gravelly or rocky rivers that have moderate to fast currents and remain relatively cool during the summer months.  The species feeds on crustaceans, insects, and other fishes and has a voracious appetite.

Distribution: The smallmouth bass is widely distributed and common in suitable habitats throughout the northern two-thirds of Illinois but extremely sporadic in the southern third and absent from many areas.

            Largemouth bass:

Diagnosis:  The largemouth bass is a rather compressed bass, pale olive, with a black or brown lateral band or row of nearly confluent blotches, vague stripes across the cheeks, a hemispherical or sickle-shaped spinous dorsal fin separated from the soft dorsal by a notch.

Ecology: It is an ecologically tolerant species that occurs in virtually all types of water, including swamps, ponds, lakes, reservoirs, creeks, and large rivers.  The preferred habitat is weedy oxbows and clear floodplain lakes.

Distribution: The largemouth bass is statewide and abundant.  It doubtlessly occurs in every township in Illinois. 

               Spotted bass:

Diagnosis:  The spotted bass is a rather compressed bass, pale olive, with a black or brown lateral band or row of nearly confluent blotches, dark stripes across the cheeks, several longitudinal rows of dark spots on the lower sides, a gently curved spinous dorsal fin broadly joined by the soft dorsal, and a moderate-sized mouth.

Ecology: The spotted bass occurs in small and large rivers that are clear, gravelly, and have moderate current.  It is most common in firm-bottomed pools.  Although occupying reservoirs in other states, in Illinois it is primarily a stream species.

Distribution: The spotted bass is a widely distributed and common species in suitable habitats in the Wabash-Ohio drainage in Illinois, and it occurs commonly in Clear Creek, a direct tributary of the Mississippi River, in southwestern Illinois.

       Rock Bass:

Diagnosis:  The rock bass is a robust sunfish, greenish or yellowish, with brown reflections and obscure brown saddles on the back and brown spots aligned in longitudinal rows along the sides, large red eyes, and a large mouth. 

Ecology: It occurs in clear gravelly rivers, often in pools with abundant vegetation or in eddies behind large boulders.   It is intolerant of silt and turbid water and is most abundant in cold, well-oxygenated water.

Distribution: The rock bass is generally distributed in clear, gravel-bottomed and rocky streams in northern and central Illinois but is extremely sporadic in the western and southern parts of the state.

     Flier:

Diagnosis: The flier is a deeply compressed sunfish, greenish or yellowish on the sides, with bronzy reflections and longitudinal rows of brown spots, a vertically aligned teardrop, reticulated median fins, and a small mouth.

Ecology: It occurs in swamps, lakes, slough, and low-gradient streams and is most abundant in well-vegetated waters.   Reproductive habits of the flier are presumably similar to those o other sunfishes, but no life history information has been published.

Distribution: The flier is generally distributed and common in suitable habitats in the southern third of Illinois.

       Banded Pygmy sunfish:

Diagnosis: The banded pygmy sunfish is a tiny slab-sided but robust sunfish, grayish, with many pepperlike dark spots over the entire head and body, punctulate fins, 10-11 vertical bands on the sides, and a rounded caudal fin.

Ecology: It is normally associated with dense beds of aquatic vegetation in swamps and sloughs.  In the banded pygmy sunfish nest-building habits are poorly developed.

Distribution: The banded pygmy sunfish occurs only in extreme southern Illinois and is common at only a few sites.

        Green sunfish:

Diagnosis:  The green sunfish is a rather shallow--bodied and robust sunfish, dark olive on the sides, with indistinct rows of greenish or coppery spots in the adult, a black spot on the posterior rays of the soft dorsal fin, thin blue-green lines on the face, a yellowish-white distal margin on the anal fin, and a large mouth.

Ecology: It occurs in small ponds and sluggish creeks but is seldom found in rivers and large lakes.  It is a pioneering species that soon finds it way into newly created farm ponds and borrow pits.

Distribution: The green sunfish is statewide in occurrence and abundant everywhere that suitable habitat exists. 

        Warmouth:

Diagnosis:  The warmouth is a shallow-bodied and robust sunfish, greenish-yellow to olive and heavily mottled with brown, with prominent dark lines radiating out of the eye, and a large mouth.

Ecology: It occurs in swamps, ponds, lakes, and streams of various sizes that are low gradient and have mud or debris over the bottom.  In streams it is a pool species and is often abundant around beds of vegetation or roots of trees or stumps.

Distribution: The warmouth is found statewide in Illinois but much more generally distributed in the southern third of the state than elsewhere.

          Orangespotted sunfish:

Diagnosis:  The orangespotted sunfish is a somewhat compressed sunfish, light olive in ground color, with many scattered spots of dark brown in the female and red or orange in the male.

Ecology: It has wide ecological tolerances, occurring in almost all types of waters except swiftly flowing streams.   In streams it occupies pools with silt or debris on the bottom.

Distribution: The orangespotted sunfish is statewide and common in suitable habitats.  It has been expanding its range within historic times and although it is now more generally distributed in Illinois than formerly, it is less common in central Illinois than it once was.

          Bluegill:

Diagnosis: The bluegill is a thin and much compressed sunfish, bluish or yellow-green, with six to eight olive, chainlike, vertical bands down the sides.

Ecology: It reaches its greatest abundance in clear well-vegetated lakes but also occurs in swamps, ponds, and in pools of streams of various sizes, especially large rivers.

Distribution: The bluegill is statewide and common, and there is no evidence that it was ever any more so than at present.

         Longear sunfish:

Diagnosis: The longear sunfish is a thin and deep-bodied sunfish, olive on the sides, with numerous spots of blue and orange, an orange breast, alternating stripes of bright blue and orange across the face, obscure vertical bands, and a very long and very flexible opercular flap. 

Ecology: It is characteristic of sand and gravel-bottomed pools of creeks and small rivers.  It avoids strong current and turbid water over a silt bottom and is less tolerant of silt and pollution than other Illinois fishes.

Distribution: The northern longear sunfish is known only from Kankakee, Will, Iroquois, and Grundy counties, where it is erratic and rare.  The central longear

            Redear sunfish:

Diagnosis:  The redear sunfish is a rather thin and deep-bodied sunfish, greenish olive on the sides with or without dark vertical bands, with a yellowish belly, dark olive lines across the face, a light-bordered and semiflexible black opercular flap with a red or orange posterior margin, unspotted greenish yellow median fins, and a rather small mouth.

Ecology: The redear sunfish originally occurred in swamps, bottomland lakes, and low-gradient streams but is most abundant in clear artificial lakes, where it has been introduced, usually along with a largemouth bass.

Distribution: The redear sunfish is native to the southern third of Illinois but now occurs, through stocking, in all parts of the state.

         Spotted sunfish:

Diagnosis:  The spotted sunfish is a moderately thin and deep-bodied sunfish, dark olive, with longitudinal rows of paler spots, a blackish face and head, a small wash of pale red just above the opercular flap, and a short and rounded pectoral fin.

Ecology: The spotted sunfish occupies well-vegetated swamps, sloughs, and bottomland lakes.  It is not known where the spotted sunfish and other species occurring over a soft bottom find areas of gravel to construct nests, and they may use debris on the bottom or submerged logs and stumps if gravel or sand cannot be found.

Distribution: The spotted sunfish presently occurs in only a few bottomland lakes and swamps along the middle Illinois River valley and in the southern tip of the state.

         White crappie:

Diagnosis: The white crappie is a thin and much compressed sunfish, white or silvery on the sides, with greenish reflections and six or seven dusky vertical bands; somewhat reticulate median fins; usually six dorsal spines; no notch between first and second dorsal fins.

Ecology: The white crappie has a wide ecological tolerances, occurring in virtually all types of water except very small streams and ponds.  It is most abundant in well-vegetated lakes and rivers.

Distribution: The white crappie is statewide and common in large rivers.  It is more widespread than indicated on the distribution map, since it occurs also in virtually all reservoirs, most of which were not collected in because of their artificial nature.

         Black crappie:

Diagnosis:  The black crappie is a much compressed sunfish, white or silvery on the sides, with greenish reflections and numerous irregular black vermiform blotches scattered over the sides as well as smaller patches of black pigment; highly reticulate median fins.

Ecology: Like the white crappie, this species occupies almost all types of water except very small streams and ponds and streams with strong currents.  The species is most abundant in well-vegetated lakes and clear backwaters of rivers.

Distribution: The black crappie is statewide and moderately common but much less so than the white crappie.  It is common in reservoirs that have suitable habitat as well as in natural lakes and backwaters.

         Eastern sand darter:

Diagnosis:  The eastern sand darter is a terete and pellucid darter with a row of 9-13 discrete brown dots along the lateral line and a similar row along the dorsal ridge, paired dusky markings on the snout, pigment distinctly outlining the several rows of scales above the lateral line, and a pronounced snout.

Ecology: It occurs in the rivers of high water quality over beds of pure sand.  It dives into the shifting sand and completely disappears for a time and then may stick only its head above the sand.

Distribution: The eastern sand darter is restricted to streams in the upper Wabash River drainage and is common only in the middle Embrarras River and Middle Fork of the Vermilion.

         Greenside darter :

Diagnosis:  The greenside darter is a rather terete and extremely snubnosed darter, grayish or greenish, with five to eight V or U-shaped dusky markings along the side, the back and upper sides tesselated with olive and two dark suborbital bars.

Ecology: The greenside darter occupies fast, deep riffles and clear raceways of large creeks and rivers over coarse gravel and rocks, which often have growths of algae.  It feeds primarily on insect larvae that live on rocks in the riffle habitat.

Distribution: It is restricted in Illinois streams in the upper Wabash River drainage of east-central Illinois.

         Rainbow darter:

Diagnosis:  The rainbow darter is a compressed darter, brownish olive, with three prominent middorsal bands; several vertical bars on the sides, each about the same width as the interspaces between them, and naked cheeks.

Ecology: It lives in clear fast riffles over gravel and rock rubble in creeks and small rivers.  It is often abundant in creeks referred to as "runs," which are margined by trees and too fast for silt to accumulate over the grave or rocky bottoms.

Distribution: The rainbow darter occurs in high-gradient streams of the upper Wabash River drainage in east-central Illinois and northward to Wisconsin on the eastern side of the state.  It does not occur in the northwestern, central, and western counties of Illinois and in southern Illinois is known only form Union, Pope, and Hardin counties.

         Fantail darter:

Diagnosis:  The fantail darter is a terete and rather slender darter, dark olive green or brownish both above and below, with the caudal fins boldly barred with black, a conspicuous humeral spot, a sharp snout, and the lower jaw projects beyond the upper.

Ecology: It occurs in fast rocky riffles of rivulets, creeks, and small rivers, usually in shallow water.  The male has well-developed knobs on the tips of the dorsal spines, and they are used to cleanse the site of egg deposition and also to clean the eggs after they have been laid. 

Distribution: The fantail darter occurs throughout most of the northern half of Illinois and is common in suitable habitats.   It is much more general in occurrence toward the north but sporadic in central Illinois.

        Johnny darter:

Diagnosis:  The johnny darter is a slender and terete darter, pale tan or straw colored, with five or six quadrate brown saddles on the back, small W or X-shaped markings on the sides that tend to be aligned along the lateral line, a complete lateral line, and a horizontal mouth.

Ecology: It is more tolerant of slow-moving water than many other darters and reaches its greatest abundance in pools of creeks that have bottoms of mixed sand, silt, and gravel.

Distribution: The johnny darter occurs in all parts of Illinois and is abundant everywhere except in the low-gradient streams of the south-central and west-central parts of the state, where it is sporadic.

        Orangethroat darter:

Diagnosis:  The orangethroat darter is a compressed darter, brownish olive, with three prominent middorsal bands, several vertical bars on the sides narrower than the interspaces between them, two anal spines, and naked cheeks.

Ecology: It occupies riffles and pools of small creeks that have bottoms of mixed sand and gravel, and it is often abundant in prairie streams that have no marginal tree vegetation.

Distribution: The orangethroat darter is abundant where it occurs but it is completely absent in several parts of the state for reasons not readily apparent.

        Logperch:

Diagnosis:  The logperch is a cylindrical darter, pale straw color olive, a conspicuous median caudal spot, a pointed and conical snout extending well beyond the mouth, and a conical snout.

Ecology: The logperch prefers clear riffles over mixed sand and gravel in large creeks and rivers, but it also occurs in clear bottomland lakes, pools of streams, and low-gradient large rivers.

Distribution:  The logperch occurs in all parts of the state where streams are large and stable enough to provide habitat.   It is particularly common in the sluggishly flowing and sand-bottomed Illinois River and its associated lakes.

        Blackside darter:

Diagnosis:  The blackside darter is a moderately slender darter, pale olive green or grayish-yellow above and whitish below, a small and inky black, median caudal spot, two anal spines, and gill covers not connected at the isthmus.

Ecology: It is most abundant in firm-bottomed pools of creeks and small rivers, but it sometimes ascends into headwaters.   Spawning occurs in May in gravelly or coarse sand riffles.

Distribution: The blackside darter occurs in all parts of Illinois, but it is far more generally distributed in the eastern than in the western  part of the state.

        Slenderhead darter:

Diagnosis:  The slenderhead darter is a slender darter, tan or pale olive, with dim and irregular brown saddles well separated from 10-12 vague and more or less confluent blotches of greenish or brownish color along the sides, a discrete median caudal spot of black, and much-produced snout.

Ecology: It is shallow raceways and riffles over sand-gravel bottoms in medium-sized to large rivers.  The occasionally occurs in primarily sand-bottomed raceways, but rarely can be found over silty bottoms.

Distribution: The preferred habitat is shallow raceways and riffles over sand-gravel bottoms in medium-sized to large rivers.   It occasionally occurs in primarily sand-bottomed raceways, but rarely can be found over silty bottoms.

        Dusky darter:

Diagnosis:  The dusky darter is a moderately slender darter, pale olive green or grayish-yellow above and whitish below.   It has two anal spines, the upper lip is bound to the snout by a well-developed frenum, and gill covers tat are moderately connected at the isthmus.

Ecology: It occupies deep raceways and riffles over a predominantly gravel bottom in medium-sized to large rivers.  It is intolerant in turbidity, silt, and pollution, and is usually found only in channels with moderate to fast currents.

Distribution: The dusky darter is restricted to the Wabash-Ohio river drainage in Illinois and is common in only a few streams of the upper Wabash River system, most notably in the middle section of the Embarras River.

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