Kingdom - Animalia

Phylum - Chordata

Classes in Illinois - Cephalaspidomorphi and Actinopterygii

Species in Illinois - 200

List of Illinois fish species

Ichthyology is the study of fishes. Scientists know of about 25,000 living fish species in 57 orders and 482 families. The number of species of fishes exceeds all other species of vertebrates combined.

Although over 97% of the surface water on earth is saltwater, about 41% of all species of fishes live in freshwater.  Fishes in ponds, lakes and streams become isolated from each other, allowing species to diverge.


  • are aquatic.
  • are ectothermic (cold-blooded) animals.
  • are vertebrates (have backbones).
  • have fins and gills throughout life.


Basic Illinois Fish Identification


Illinois has approximately 200 species of fishes in 18 orders. Below are some tips to help you identify some of the major groups.


Things to look at to identify a fish:

  • Fins
  • Body color or pattern
  • Shape


Perciformes - Perch-like

Centrarchidae - sunfishes &basses

  • at least three anal spines,
  • 5-7 branchiostegal rays,
  • separate gill membranes


Smallmouth Bass

Siluriformes - Catfish

  • adipose fin present,
  • spine like rays on dorsal and pectoral fins,
  • body without scales or covered in bony plates,
  • barbels on head



Esociformes - Pikes, Muskellunge & Mudminnows

  • no adipose fin,
  • dorsal fin located posterior



Cypriniformes - Carps & Minnows

  • adipose fin absent,
  • head usually scaleless,
  • kinethmoid present



Perciformes - Perch-like

Percidae- perches, darters & walleye

  • dorsal fins separate,
  • 1 or 2 anal spines,
  • 1 spine and 5 rays in pelvic fin


Rainbow Darter

Salmoniformes - Salmons and Trouts

  • adipose fin present,
  • gill membranes extend far forward,
  • pelvic axillary process present (spine scale near pelvic fin)

Rainbow Trout.png

Rainbow Trout

Lepisosteiformes - Gars

  • body and jaws elongate,
  • mouth with needle-like teeth,
  • dorsal fin far back,
  • tail fin abbreviate heterocercal (top lobe longer than bottom lobe)

gar.pngLongnose Gar

Petromyzontiformes – Lampreys
Acipenseriformes – Sturgeons and Paddlefish
Amiiformes – Bowfins
Osteoglossiformes – Mooneyes
Anguilliformes – Freshwater Eels
Clupeiformes – Herrings and Shads
Percopsiformes – Trout and Pirate Perch
Gadiformes - Burbot
Atheriniformes - Silversides
Cyprinodontiformes - Topminnows
Gasterosteiformes - Sticklebacks
Scorpaeniformes - Sculpins

There are 19 endangered fish species in Illinois: lake sturgeon, western sand darter, bluebreast darter, harlequin darter, cypress minnow, bigeye chub, pallid shiner, northern brook lamprey, redspotted sunfish, sturgeon chub, greater redhorse, river chub, pugnose shiner, bigeye shiner, blacknose shiner, taillight shiner, weed shiner, northern madtom, and pallid sturgeon. The pallid sturgeon is also listed as  federally endangered.

An additional twelve fish species are threatened: eastern sand darter, longnose sucker, cisco, gravel chub, Iowa darter, banded killifish, starhead topminnow, least brook lamprey, Bantam sunfish, river redhorse, ironcolor shiner, and blackchin shiner.  Nine species have become extirpated (extinct from Illinois).


Some past articles published in INHS Reports:

Largemouth Bass Recruitment and Stocking Strategies. Summer 2001

Physiological Telemetry in Fisheries Research. Spring 2001

Database Management and Analysis of Fisheries in Illinois. Fall 2000

Smallmouth Bass and Artificial Reefs in Lake Michigan. May-June 2000

Effects of Common Carp (Cyprinus carpio), an Exotic Fish, on Aquatic Ecosystems. January-February 2000

Quality Management of Bluegill Population Size Structure. July-August 1999

Species Spotlight: Orangethroat Darter. May-June 1999

The Naturalist's Apprentice: So Many Fishes! How can You Tell Them Apart?. May-June 1999

Development of an Individual-based Model to Evaluate Growth and Survival of Walleye. May-June 1999

INHS Fish Collection. March-April 1999

Development and Application of a Gambusia Bioenergetic Model. January-February 1999

The Round Goby: An Example of the "Perfect" Invader?. November-December 1998

The Bighead Carp (Hypophthalmicthys nobilis) in Reach 26 of the Mississippi River . November-December 1998

Channel Catfish Populations in the Upper Mississippi River System. September-October 1998

Hydroacoustics: A Tool for Understanding Fish-Habitat Associations in Rivers. November-December 1997

Understanding Large-river Fish Communities. September-October 1997

Differences in Food Consumption and Metabolic Rates Between Walleye Stock. July-August 1997

River Levels and Largemouth Bass Populations in the Illinois River. March-April 1997

Predicting Juvenile Fish Abundance from Charactersistics of the Spring Flood. January-February 1997

Critical Factors in the Early Life History of Illinois Fishes. November-December 1996

The Distribution of Aquatic Organisms in the Central Highlands. July-August 1996

Illinois River Fish Communities: 1960s Vs. 1990s. May-June 1996

Effect of Electrofishing on Sunfish. March-April 1996

Identification of Genetic Stocks in Midwest Game Fish. January-February 1996

The Round Goby Invades Lake Michigan. November-December 1995

Factors Affecting Growth of Reservoir Fish. May-June 1995

Small Impoundment Fisheries Research at Ridge Lake Station. March-April 1995


INHS Fish Collection