American brook lamprey:

Diagnosis- The adult of the American lamprey has a pair of prominent supraoral teeth">

        American brook lamprey:

Diagnosis- The adult of the American lamprey has a pair of prominent supraoral teeth, usually three pairs of bicuspid lateral teeth, and a row of infraoral teeth; peripheral teeth are present but smaller, those on the posterior field are often hidden.  The dorsal fin is distinctly bilobed with a wide notch between the lobes.  This species is usually tawny gray to almost black above and tan to grayish white below.

Ecology- Both ammocoetes and adults are found in rather fast riffles and clean gravelly raceways of large creeks and small rivers.   Spawning in northern Illinois occurs in late April and early May.  Ammocoetes and newly transformed adults of the American brook lamprey have been found in the Kankakee River along with comparable stages of the northern brook lamprey and the silver lamprey, suggesting that several lamprey species utilize the same spawning sites

Distribution- The species is now rare and erratic in distribution but probably more generally distributed than available records indicate.  Historical studies have records that give the impression that it was once abundant in streams in northern Illinois and that it was widely distributed in all parts of the state.

    Lampetra-American brook lamprey.jpg (87415 bytes)

      Shovelnose Sturgeon:

Diagnosis- The shovelnose sturgeon differs from the lake sturgeon by the same characters that distinguish the pallid and lake sturgeon.  It differs from the pallid sturgeon most obviously in its inner barbel that is much more than half the length of the outer, the presence of scutes on the belly, its fewer dorsal rays and anal rays, its darker color, and its smaller maximum size.

Ecology- This species is much more common than the pallid sturgeon, but its life history is almost as poorly known.  The adults ascend tributaries and spawn from April to June.  Males become sexually mature at about 20 inches and females at about 25 inches.  Spawning takes place in swift chutes such as boulder riffles, and old dam sites.

Distribution- The shovelnose sturgeon is found in the Mississippi River down the entire length of Illinois.  They are also located in large tributaries as the Illinois, Kaskaskia, Vermillion and Big Muddy rivers.

Scaphirhynchus-Shovelnose Sturgeon.jpg (22393 bytes)

        Lake Sturgeon:

Diagnosis-The lake sturgeon differs from other species of sturgeons by its pointed, rather conical snout; robust body; partially plated terete caudal peduncle: smooth and subequal barbels; and the two smooth lobes on the lower lip.

Ecology- The lake sturgeon lives on the bottom of large rivers and in the shallow waters of large lakes.  The adults migrate to areas of rocky rapids or shoals with strong wave action to spawn in the spring.   Large females lay hundreds of thousands of adhesive eggs, which require 5 days to hatch at water temperatures of 15-18 degrees C.  Growth is relatively slow and sexual maturity is reached in 15-20 years.

Distribution- The lake sturgeon was reportedly "very abundant" in Lake Michigan and preset in large rivers of the state before 1880.  Recently, reports have shown that they can be found in the Rock River, Mississippi river, and are more common to  Lake Michigan than Illinois rivers.

Acipenser-Lake Sturgeon.jpg (21807 bytes)        


         Shortnose gar:

Diagnosis-The adult shornose gar is readily separable from the longnose gar by its much shorter and wider beak, but it has a body shape and proportions similar to those of the spotted gar.  It differs from the spotted gar in lacking discrete dark spots on the head, beak, and front half of the body.

Ecology- The shortnose gar is presumably similar to the longnose gar in life history and behavioral aspects but differs somewhat in habitat.  It is the common species of very large rivers and lowland lakes, and though it can tolerate silty water, it is take commonly over a sand bottom as well as over mud.

Distribution- The species is extremely abundant in the Mississippi, Ohio, and middle Illinois rivers.It does not occur in the glacial lakes nor anywhere in the northeastern part of Illinois.  It is restricted to the major rivers, their marginal lakes, and lower reaches of larger tributaries.

Lepisosteus-Shortnose gar.jpg (50564 bytes)

        Longnose gar:

Diagnosis-The adult longnose gar is easily recognized by its extremely long and slender snout, its width at the nostrils being less than the eye diameter, and the distance from the rear edge of the orbit to the back of the operculum going more than 3.5 times into the head length.

Ecology- The longnose gar occurs in lakes and streams and is the common gar of small rivers and large creeks.  Adults are most often found in deep quiet pools; juveniles, n shallow, weed shoreline areas.

Distribution- The longnose gar is distributed statewide and is relatively common.  It is the only gar in the glacial lakes of northwestern Illinois.  It is much less common in the Mississippi river and most of the Illinois river than the shortnose gar, but it occurs in more of the smaller rivers.

        Lepisosteus-Longnose gar.jpg (20250 bytes)


Diagnosis- The bowfin is so distinctive in its generic characters that it can hardly be confused with other Illinois fish.  The young superficially resembles the adult mudminnow but differs from it in having a long dorsal fin; heterocercal tail; and a different pattern, the most conspicuous field characters being the large black caudal spot and thin dark stripes through the face.

Ecology-  The bowfin occurs in oxbows and backwater pools of rivers, lakes and swamps.  It prefers relatively shallow, clear, well-vegetated waters and can often be seen at night foraging along the shoreline.   Spawning occurs in the late spring and early summer, depending on latitude.

Distribution- Although still locally abundant, the bowfin is less generally distributed because of the drainage of naturals lakes and swamps marginal to large rivers and the loss of clear, well-vegetated aquatic habitats.  The species is still rather general in swampy areas in the southern third of the state, in sloughs adjacent to large and medium sized rivers throughout the state, and in some of the glacial lakes in the northeastern Illinois.


        Amia-Bowfin.jpg (47715 bytes)

        American eel:

Diagnosis- The American eel has a snakelike body and is sufficiently distinctive that it cannot be confused with other Illinois fishes.  It differs most conspicuously from lampreys in having jaws, paired pectoral fins, two nostrils, and only one gill slit on each side.

Ecology- The American eel is said to prefer deep pools with mud bottoms, but it is occasionally found in large creeks, lakes, ponds, and even on land when migrating back to the sea.

Distribution- It occurs throughout Illinois where water quality is such that fish can survive, except in the Lake Michigan drainage.  It is extremely sporadic and now most often taken in large rivers, but it can appear almost anywhre upon occasion.


Anguilla-American eel.jpg (51846 bytes)


        Skipjack herring:

Diagnosis- The skipjack herring is readily distinguished from other clupeids by its elongate and much compressed body, silvery coloration, the prominently protruding lower jaw, and the presence of teeth in both jaws.

Ecology- It occurs in clear, fast water over sand and gravel in large rivers.  It is a schooling fish and derives its common name from its habit of leaping out of the water.

Distribution- The skipjack herring is found occasionally throughout the length of the Illinois River and in the Mississippi River downstream, but is more common in the Wabash and Ohio rivers.

Alosa-Skipjack herring.jpg (74714 bytes)

        Gizzard shad:

Diagnosis- The gizzard shad is a compressed white or silvery fish with a saw-toothed midventer, a dorsal fin with the last ray prolonged into a long filament, and an inferior or subterminal mouth.  It can be distinguished from the threadfin shad by the position of its mouth, its smaller scales, and its higher anal ray count.

Ecology- Spawning occurs in April, May, and June.  Breeding adults aggregate and eject quantities of eggs and sperm while swimming close together.  It is often the most abundant fish in reservoirs and oxbows and may make up most of the biomass.  In streams it is usually found in deep, quiet pools with silt and debris on the bottom.

Distribution- The gizzard shad is statewide in distribution and abundant everywhere except in extreme northeastern Illinois.   It is more common and general in occurrence over most of the state and has probably expanded because of the construction of reservoirs and ponds.

Dorosoma-gizzard shad.jpg (53115 bytes)


        Rainbow trout:

Diagnosis- The rainbow trout has many small black or brown spots scattered over the top of the head, back, sides, and caudal fins; usually a red or orange band along each side; an anal fin base greater tan the height of the fun; and fewer than 12 principal rays in the anal fin.

Ecology-  Near the ocean the species is anadromous, and the sea-run adult, called a steelhead, is more nearly unicolorous.   Elsewhere the species is not migratory.  It occurs in lakes and streams with cold, higly oxygenated waters.  Spawning occurs early in the spring in which the female deposits several hundred eggs.

Distribution- The rainbow trout is native to the Pacific Coast of North America.  More recently, the rainbow trout has been stoced in streams of northern Illinois, Iowa, and Wisconsin and in Lake Michigan.


Oncorhynchus-rainbow trout.jpg (97423 bytes)

        Chinook Salmon:

Diagnosis- The chinook salmon attains a larger size, up to 900 mm, than the coho salmon.

Ecology- It has a life history and habits similar to those of the coho.

Distribution- Although it is one of the most important commercial species of salmons in western North America, it is insignificant in Illinois.

Oncorhynchus-Chinook salmon.jpg (41771 bytes)


        Grass pickerel:

Diagnosis- The grass pickerel is at once recognizable as a pike by its ducklike beak.  It can be distinguished from the muskellunge and norther pike by its fully scaled cheeks and opercles and prominent dark suborbital bar.

Ecology-It is most common in quiet pools of streams, especially those containing aquatic vegetation.  It is also common in marshes, sloughs, and swamps and is tolerant of turbid water although it prefers clear water.  Spawning occurs in March and April

Distribution- The grass pickerel occurs in all parts of the state but is extremely sporadic in western Illinois.  It is still common in the southern and eastern parts of the state but less generally distributed than formerly.

Esox-americanus-Glass pickerel.jpg (75725 bytes)

        Northern pike:

Diagnosis- The northern pike is distinctive because of its pattern of light-colored markings on a green or brown ground color.   It also differs from other species in the genus in having fully scaled cheek, but only the upper half of the opercule is scaled.

Ecology- The pike occurs in lakes, marshes, pools of creeks, shallow backwaters and in flooded weedy bottomland.  The female, attended by one or more males, scatters many thousands of eggs that adhere to vegetation and debris over the bottom, during spawning.

Distribution- It was once abundant in the Illinois River, but by 1900 had greatly decreased.  The species still occurs rather generally throughout the northern third or Illinois.  It occurs in the Illinois River as far south as Havana and in the Mississippi River almost to the mouth of the Ohio River.

Esox-lNorthern pike.jpg (37841 bytes)

        Banded Killifish:

Diagnosis- The banded killifish is a slender and teret topminnow, which is light olivaceous above and silvery white below with the dorsum tesselated with brown, and with many thin, well-separated, dark vertical bars along the sides in both sexes.

Ecology- It occurs in clear glacial lakes with much aquatic vegetation.  It is usually in schools of a few to many individuals that cruise about the surface of weedy lakes.  Spawning occurs in the late spring and early summer.

Distribution- The banded killifish still occurs in a few glacial lakes in Lake and Cook counties and is common in some of them.   It once occurred in McHenry County and, as isolated populations, in McLean County.

Fundulus-Banded killifish.jpg (50069 bytes)

        Black topminnow:

Blackstriped topminnow.jpg (11376 bytes)

        Starhead Topminnow:

Diagnosis- The starhead topminnow is a rather deep-bodied killifish, olive above and yellow on the sides with minute flecks of red, blue, or green, with a prominent blue-black blotch or tear drop beneath the eye.

Ecology- It occurs in some glacial lakes and in clear, well-vegetated floodplain lakes, swamps, and marshes.  Spawning occurs in late spring and early summer among dense beds of aquatic vegetation.

Distribution- It is extremely sporadic in Illinois but often common in those few lakes and swamps where it occurs.  The reason for this erratic behavior is unknown.

Fundulus-Starhead topminnow.jpg (35306 bytes)

        Blackspotted Topminnow:

Diagnosis-The blackspotted topminnow is a terete killikfish, pale olive or yellowish above and white below, with a broad, purplish-black, lateral band extending from the snout tip to the caudal fin and a few to many discrete and intense black dots on some of the scales above the lateral band.

Ecology- The habitat relationships of the blackspotted and blackstriped topminnows differ markedly in different parts of their ranges.  The blackspotted topminnow is almost entirely restricted to clear, gravelly, upland streams of high gradient (in Illinois). 

Distribution- It is extremely abundant in the clear fast streams of the Shawnee Hills.  It occurs in some of the slower, more turbid streams along the northern border of the Shawnee Hills but is restricted to the southern fifth of Illinois.

Fundulus-Blackspotted topminnow.jpg (63546 bytes)

         Brook silverside:

Diagnosis-The brook silverside is an extremely slender and frail little fish, pale straw color above and silvery below, with a somewhat pellucid body.  It has a distinct beak, two separate dorsal fins (the first short with four to six weak spines), and a long anal fin. 

Ecology- It is a surface-dwelling fish with a strong schooling tendency.  It occurs in lakes, ponds, small rivers, and sometimes in brooks that are clear and have quiet water.

Distribution- The brook silverside is statewide in occurrence, but in Illinois is usually associated with large rivers and their marginal waters.  Where is occurs it is abundant, but it is not ubiquitous by any means.


Labidesthes-Brook Silverside.jpg (4686 bytes)



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