Wild About Illinois Fishes!

Illinois is home to a wide variety of fish species. At present 34 families of fishes are represented in the state's waters. Because so many species exist, the fish exhibit a wide range of habits and characteristics.

The information contained in these pages is Illinois specific as much as possible. All families are briefly characterized and all Illinois species for each family are listed. If you are unfamiliar with vocabulary terms relating to fishes, you will benefit from reading the vocabulary section before looking up the family and species descriptions. The same is true for fish anatomy.

Kingdom: Animalia - Animals are multicellular organisms that rely on other organisms for nourishment. There cells do not have cell walls. Most animals are capable of movement at least in some portion of their life cycle. Reproduction is generally sexual, but in some animals asexual reproduction may be utilized at certain times.
Phylum: Chordata - The Phylum Chordata contains the vertebrate animals. Mammals, birds, reptiles, amphibians and fishes are included in this phylum. These animals have a notochord at some point in their development. They have a tubular nerve cord along the back. Gill slits and a tail are present at some point in their life cycle. They have an internal skeleton.

Class Cephalaspidomorphi - (Lampreys) These fishes do not have jaws. They do not have paired fins. The body is cylindrical and has a cartilage skeleton.
Order Petromyzontiformes - The lampreys have teeth on both the tongue and the oral disc. They have seven gills. They have one or two dorsal fins.

Class Actinopterygii - (Ray-finned Fishes) The bony fishes have a skeleton made of bone. All of the gill openings are covered by one flap. The pectoral and pelvic fins are paired. They are found in both fresh and salt water.
Order Acipenseriformes - The sturgeons and paddlefishes have a skeleton that is maily made of cartilage. The upper lobe on the tail is longer than the lower lobe. They have a spiral valve in the intestine, and a notochord that is present throughout their life.

Order Lepisosteiformes - The gars have a cylindrical body that is covered with diamond-shaped scales. The long snout has sharp teeth. The dorsal and anal fins are placed near the tail. The swim bladder may be used for breathing when the amount of dssilved oxygen in the water decreases significantly.

Order Amiiformes - The bowfin has round scales. Its tail appears to be of equal size in the upper and lower regions. It has a bony plate under the lower jaws.

Order Hiodontiformes - This group of freshwater fishes has teeth on the tongue and roof of the mouth and fewer than 16 rays in the tail fin. Members of this group are found in North America, South America, Africa, Asia and Australia. Only two species, the mooneye and the goldeneye, are found in North America.

Order Anguilliformes - Eels may be found in fresh and salt water. The head is wedge-shaped and has a hard mouth. There are no pelvic fins on the long, thin body.

Order Clupeiformes - The herrings and shads live near the water's surface and eat plankton. They have silvery scales. The body is flattened side to side. The swim bladder is connected to the inner ear and thus increases the ability of these fishes to hear sounds.

Order Cypriniformes​ - The minnows, suckers and others make up this very large order of fishes. They have a chain of bones that connects to the swim bladder to the inner ear which aids the fish in hearing. The pelvic fins are located on the belly of the fish. Most are small in size. Maturity is reached quickly.

Order Siluriformes

Order Esociformes

Order Salmoniformes - Most members of this group have an adipose fin on the back near the tail fin. The pelvic fins are located on the belly. The scales are large and round.

Order Percopsiformes - These small, North American fishes include the trout-perches, cavefishes and pirate perch. If pelvic fins are present, they are placed very close to the pectoral fins. Spines in fins are not well-developed. Scales are ctenoid (rough-edged) or cycloid (smooth-edged).

Order Gadiformes - The codfishes and hakes have an elongated body with long dorsal and anal fins. The scales are small and round. Barbels are usually present near the mouth.

Order Cyprinodontiformes

Order Mugiliformes

Order Atheriniformes - These fishes live near the surface of the water body. The mouth is upturned at the end of the flattened head. The dorsal fin is located near the tail. The pelvis fins are absent on some species. The lateral line tends to be developed on the head but absent from the rest of the body.

Order Gasterosteiformes - The fishes in this order include seahorses, pipefishes and sticklebacks.

Order Scorpaeniformes - These bottom-dwelling fishes may be found in both marine and freshwater environments. They have large, rounded pectoral fins, a big head, a round tail fin and spines and/or bony plates on the head and body. This order includes sculpins, rockfishes and many other species.

Order Perciformes - These fishes have a deep body, two dorsal fins and a large mouth. Most are active during the day.

​adipose fin - fin located between the dorsal and caudal fins; present on some fishes

anal fin - fin located on the undersurface usually behind the anus

caudal fin - tail fin

ctenoid scale - scale with a toothed rear edge

cycloid scale - scale with a smooth rear edge

dorsal fin - fin located in the middle of the back; it may be notched or divided

exotic species - a species that is not native to an area

extirpated species - one that has been eliminated from a portion of its range, in this case, Illinois

federally endangered species - any species which is in danger of extinction throughout all or a significant portion of its range

nonnative - exotic species

pectoral fin - one of a pair of fins that are attached just behind the head

pelvic fin - one of a pair of fins on the lower part of the body

spawning - depositing eggs in the water

state endangered species - any species which is in danger of extinction as a breeding species in Illinois

state threatened species - any breeding species which is likely to become a state endangered species within the foreseeable future in Illinois

thoracic - on the breast of the fish

Fish or Fishes? The term "fish" is used when referring to one species of fish, no matter how many individuals are present. The term "fishes" is used when more than one species of fish is referred to.

Fish Fact: Fishes have been found in farm fields and streets after heavy rains, but it does not rain fishes! These fishes swam there from nearby water bodies during high water after the storm and became stranded.

Fish Fact: The grass carp is the largest member of the minnow family in Illinois and was introduced into the state in the 1970s from China.

Use this diagram to help you learn the name and location of several fish structures.

Fish Fact: Many fish can change color to match their surroundings by expanding or contracting pigment cells in the skin.  

All photographs included on this Wild about Fishes Website are copyright protected. None of these photographs may be used on the Internet, in publications or in any other form of media without the written permission of the photographer. All rights reserved.

Burr, B. M. 1997. Illinois Chapter of the American Fisheries Society: Minnows of Illinois continuing education seminar. Monticello, Illinois.

Illinois Department of Natural Resources. 1996. Illinois fisheries resources: trends, problems, solutions. Illinois Department of Natural Resources, Springfield, Illinois. 30 pp.

Illinois Department of Natural Resources. 1989. What fish is this? Illinois Department of Natural Resources, Springfield, Illinois. 44 pp.

Moyle, P. B. and J. J. Cech, Jr. 1982. Fishes: an introduction to ichthyology. Prentice-Hall, Inc., Englewood Cliffs, New Jersey. 593 pp. 

Page, L. M. and B. M. Burr. 1991. A field guide to freshwater fishes of North America north of Mexico. Houghton Mifflin Company, Boston/New York. 432 pp.

Pflieger, W. L. 1975. The fishes of Missouri. Missouri Department of Conservation, Jefferson City, Missouri. 343 pp.