Rife with freshwater resources, Illinois has thousands of clean streams and rivers extending throughout the state and over its borders on all sides. With over 100,000 ponds and lakes, it is a haven for countless aquatic species. Both surface waters and ground waters flow into biologically significant aquatic systems, many of which house a unique ecology of native flora and fauna.
Some of Illinois’s most diverse stream systems include tributaries that flow into one of the most important lakes in all of North America – Lake Michigan. Moreover, some of these streams consistently deliver essential nutrients and fish communities to the Mississippi River. To say that the state of Illinois is “well-watered” does justice to its favorable position on the US map. It is practically surrounded by water on all sides!
Despite the obvious importance of the state’s freshwater systems, many of them are in danger of being ecologically altered due to anthropogenic activities. As a result, a handful of fish species are threatened and endangered. Fortunately, concerted efforts to conserve the diversity of these vital water bodies continue to receive both federal and voluntary support. These natural waters are home to the valuable species listed below.
Illinois Freshwater Fish
1) Largemouth bass (Micropterus salmoides)
Among Illinois’s native black bass species, the largemouth is the most popular and most widely distributed. Highly adapted to the conditions of temperate lakes and ponds, this apex predator prefers to stay close to the vegetated portions of weedy lakes and clear backwaters. It’s especially drawn to the shallows during its feeding period. It seldom ventures into areas without vertical vegetation as its preferred prey types tend to hide in the weeds.
On average, largemouths measure around 10+ inches (25 cm) long in Illinois. The largest of their kind can measure as much as 30 inches (76 cm) long in productive lakes and ponds! The best time to search for them is when they seek out shallow littoral zones in spring.
2) Bluegill (Lepomis macrochirus)
Distinguished by its blue-to-black gill flap and the golden-orange hues of its throat, the bluegill is the most abundant sunfish species in all of Illinois. Found in practically all natural and considerably-sized waterbodies, it tends to feed in calm ponds and lakes. This species’ favorite treats include insects and their aquatic larvae.
Bluegills favor mild to warm temperatures, but they may migrate into cooler waters if they find summer temperatures uncomfortable. As they are social fish, they tend to congregate while feeding and building their nests. If temperature conditions are agreeable, they are likely to spawn repeatedly from spring to midsummer. Many larger fish rely on them as a live and protein-rich food source.
3) Walleye (Sander vitreus)
Walleyes are usually active at night, during the early or late hours of the day, and when water conditions are choppy. They are named for the opaque appearance of their specialized eyes, which are equipped with modifications for seeing in low-light conditions. They tend to avoid shallow and sun-exposed areas and prefer to prey on fish with poorer eyesight.
In Illinois, walleyes are mainly found in northern rivers and gravelly lakes. Their densest populations occur in the windswept waters of the Rock, Mississippi, and Kankakee Rivers. Here, they grow to an average length of about 14 inches (36 cm) and may weigh as much as 15 pounds (6.8 kg) each!
4) Smallmouth bass (Micropterus dolomieu)
Muscular, slender, and fast, the smallmouth bass is an angler favorite wherever it is found. To meet the demands of sport fishers all over North America, it has been introduced into major lake systems in practically all states and provinces. This feisty fish favors stream systems with a mild to moderate current and gravelly substrates. It is also found in rocky reservoirs with clear waters.
Illinois’s largest smallmouth bass populations are found in the northern regions of the state. There, they feed on smaller fish, insects, larvae, crayfish, and other crustaceans. They are best fished when water temperatures are moderately warm. In mid to late spring, they construct their nests in the rough substrates of shallower waters.
5) Sauger (Sander canadensis)
In terms of appearance, the sauger closely resembles the walleye, which is its close cousin. To differentiate the two, anglers usually examine the dorsal fin and dark pigments along the flanks of their catch. Unlike walleyes, saugers have spots along the entire length of their first dorsal fin. Saugers are also more likely to have pigmented blotches on their sides.
In Illinois, sauger populations are largely restricted to the Mississippi River. Elsewhere, walleye populations are more likely to dominate. This species favors large rivers as it is tolerant of murky conditions. In productive systems, it feeds on smaller fish, aquatic insects, frogs, and crayfish. To catch saugers, increase your chances of success by using minnows as a lure.
6) Black crappie (Pomoxis nigromaculatus)
Black crappies are now found all throughout the mainland US, where they favor deep and relatively large lakes with hard bottom substrates. As they have a high tolerance for a wide range of water temperatures, they can easily form established populations outside of their native range. Moreover, they are remarkably prolific. This means that they can overpopulate freshwater bodies that are devoid of apex predators.
Compared to the white crappie (P. annularis), with which it shares a similar appearance and near-identical food and habitat preferences, the black crappie is likely to be more dominant in Illinois’s northern waters.
7) Lake whitefish (Coregonus clupeaformis)
Often distinguished by its humpback appearance, which is caused by having a small head relative to the length of its body, the lake whitefish is one of the most commercially important freshwater species in the US. Its delicate and flavorful meat is constantly in demand due to widespread acceptance from local consumers, particularly those situated in the states around the Great Lakes System.
Anglers prefer to search for this species in both summer and winter. As whitefish can be caught using a simple setup with midges or mayflies as bait, even amateur anglers are able to enjoy targeting it. Its constantly replenishing populations are crucial for the survival of larger predatory fish, including burbot, northern pike, and lake trout.
8) Green sunfish (Lepomis cyanellus)
Indigenous to the Great Lakes and many other freshwater basins in the US and Canada, the green sunfish has a fairly widespread distribution. It can quickly form established populations in practically any type of water body, including farm ponds and polluted systems. Known for having a high tolerance to poor water conditions, it may become invasive in waters with rich structural diversity.
As the green sunfish has a large mouth compared to the size of its body, it can feed on a wide range of prey types. Regardless, most populations have shown a preference for aquatic insects and their larvae. From May to June, they form nesting congregations close to the shoreline. In the process, they may drive out the spawning populations of other sunfish species.
9) Lake sturgeon (Acipenser fulvescens)
Currently an endangered species, the lake sturgeon is an enormous freshwater fish with many seemingly prehistoric traits. Often feared due to its resemblance to sharks, its skeleton is highly cartilaginous. It is distinguished by its streamlined appearance and the rows of bony plates and armor-like scutes along its sides and back.
This enormous freshwater fish, which can grow to about 7.25 feet (2.2 meters) long, is actually a gentle giant. As a bottom feeder, it favors macroinvertebrates and small fish found along the surface of substrates. In Illinois, targeting it as a sport fish is considered illegal. Fortunately, its numbers in local waters are reportedly on the rise.
10) Yellow perch (Perca flavescens)
Also referred to as the striped perch, ring-tail perch, lake perch, and raccoon perch, the yellow perch is a common perciform throughout its native range. In Illinois, its populations are most dense in the northern half of the state, where it favors conditions in clear, natural streams and lakes with ample vertical vegetation.
This schooling fish can easily be caught as it readily takes bait and is not a particularly strong fighter on the line. It is one of the most commonly caught fish along Chicago’s freshwater coastline because it can be fished all year round. Measuring around 6.5 inches (16.5 cm) on average, it subsists on a diet of smaller fish, crustaceans, aquatic insects, and zooplankton.
11) Channel catfish (Ictalurus punctatus)
The most widespread and commercially important catfish in the US, the channel cat is a remarkably tough and hefty freshwater species. To meet angling and commercial demands for this fish, it is intentionally stocked into private ponds and intensive aquaculture systems. In the wild, though it survives in just about any type of stream or basin, it is most abundant in gravelly rivers with a rapid current.
The channel catfish measures an average length of about 18 inches (45.7 cm) in the waters of Illinois. It is an omnivorous species with a propensity to feed on just about any living thing it comes across along the bottoms of water bodies. Though it has well-developed eyes, it chooses its food using its senses of touch and taste.
12) Grass carp (Ctenopharyngodon idella)
Although grass carp is not originally found in North America, it now has naturalized populations in many freshwater systems across the continent. This herbivorous fish has intentionally been stocked into many lake systems as a means of biological control for invasive flora. It also feeds on several types of algae, which can be troublesome in fully exposed ponds with high nutrient levels.
Nowadays, it is illegal to introduce any form of grass carp (including hatchery-bought triploids) into the natural waters of Illinois. However, a permit can be obtained for stocking this species into private pond systems. If you’re interested in adding this fish to your pond, keep in mind that it can grow to enormous sizes. Non-conservative stocking densities can negatively affect your pond’s ecology.
13) White bass (Morone chrysops)
Indigenous to the area around the Great Lakes system, the white bass is a temperate perciform. It is distinguished by its notably white flanks and belly. Along the length of its sides are sets of dotted, horizontal stripes. Its back and the region around its dorsal fins tend to be much darker compared to the rest of its body.
The white bass is readily found in the large streams of the Mississippi and Illinois river systems. It is also known for thriving in major tributaries and lakes along the northern half of the state. This species usually spends most of its day in deeper waters, where it feeds on smaller fish like minnows and shad.
14) Bowfin (Amia calva)
Considered a relict species as it is the sole surviving member of its order, Amiiformes, the bowfin is often described as “primitive”. Capable of respiring in water and breathing atmospheric air, it can survive in still lakes with low dissolved oxygen conditions. Interestingly, the bowfin’s closest living relatives look nothing like it. Based on genetic studies, the DNA sequence of bowfins is more similar to that of freshwater gars than any other group of fish!
Bowfins are found all throughout the state of Illinois. They favor calm and slow water bodies, where they can hide from their potential prey behind curtains of vertical vegetation and weeds. These nocturnal, ambush predators expertly feed on smaller vertebrates and arthropods.
15) Flathead catfish (Pylodictis olivaris)
The flathead catfish is able to thrive in a wide variety of freshwater bodies, from deep rivers to shallow, vegetated basins. Popular among anglers all across the US, many catfish enthusiasts claim that it has the tastiest flesh. This is likely due to its preferred diet of live baitfish, crayfish, and smaller specimens of its own kind. Anything that makes vibrations along the benthos is not safe from this voracious predator.
Widely distributed throughout Illinois, the flathead catfish or “mudcat” prefers to stay close to submerged wooden structures. It builds and aggressively guards its nests, which are situated around or underneath logs and large pieces of fallen debris. Its spawning period takes place from June to July, when water temperatures rise to above 70˚F (21˚C).
16) Muskellunge (Esox masquinongy)
The muskellunge is a predatory fish with a streamlined, elongated body. Its longest specimens measure up to 6 feet (1.8 meters) long, but it’s quite rare to come across specimens that are longer than 48 inches (122 cm). In the wild, this freshwater fish favors clear waters with rocky outcrops and vertical vegetation. As it searches for prey, it slowly lurks through buoyant weeds.
Apart from eating smaller fish, muskies may occasionally feed on frogs, snakes, ducklings, and small mammals that attempt to cross bodies of water. Widespread throughout Illinois, their preference for water depth is largely determined by temperature and structural diversity. As they have a relatively slow reproductive rate, overfishing can decimate their local populations.
17) Lake trout (Salvelinus namaycush)
Once restricted to the cold-water lake systems of Canada, Alaska, and the Great Lakes region, lake trout is now widely distributed across the US. This slow-growing fish has more than a dozen common names, but the most popular ones are lake charr, togue, mackinaw, and namaycush. Due to its feisty behavior and its protein-rich flesh, it is commercially valued as a food and game fish.
In Illinois, lake trout populations are largely restricted to Lake Michigan. This fish was once an apex predator in the lake. Due to the introduction of more voracious salmonids, however, its status has since dwindled. Moreover, due to heavy demand for its meat, its wild populations have become compromised. In an effort to replenish its populations, hatchery-grown trout fingerlings are now frequently stocked into lakes.
18) Longnose sucker (Catostomus catostomus)
The longnose sucker is a cold-water cyprinid that favors conditions in clear streams, pools, and lakes. Some of its wild populations are known for venturing into slightly brackish waters as well. Often targeted as a game and food fish due to its moderate size, it can weigh up to 3.3 kg (7.3 pounds) and measure up to 25 inches (64 cm) long.
In Illinois, the longnose sucker is usually found in shallow waters that are connected to Lake Michigan. As made evident by the appearance of its sucking mouth, it has evolved to feed on aquatic plants, algae, small fish, and crustaceans found along the bottom reaches of its habitat.
19) Coho salmon (Oncorhynchus kisutch)
Known for their red flanks, deeply-colored heads, and their dark bellies, coho salmon are a commercially important member of the Salmonidae family. With wild populations that are anadromous, migrating between freshwater tributaries and the Pacific Ocean to spawn and feed, they are tolerant of a wide range of conditions. Those found in the Great Lakes belong to landlocked populations. Hailing from ancestors that were introduced in the 1900s, these fish spend their entire life cycle in freshwater environments.
Mature coho salmon enter the tributaries of Lake Michigan to spawn. Their hatchlings eventually make their way into the main lake basin. As they grow, their diet increasingly becomes composed of smaller fish, such as the alewife (Alosa pseudoharengus).
20) Slimy sculpin (Cottus cognatus)
The slimy sculpin spends the majority of its time along the rocky bottom substrates of deep lakes and rivers. This somewhat elusive freshwater fish prefers to remain hidden under fallen logs and large rocks. Nocturnal, it is most active when it feeds on benthic insects, small crustaceans, and the eggs of other fish species.
When the slimy sculpin moves from place to place, it doesn’t swim as a normal fish would. Instead, it slowly “hops” from one spot to another. This movement is largely facilitated by its oversized pectoral fins, which allow it to remain perched on the benthos.
21) Northern pike (Esox lucius)
The northern pike is an elongated freshwater species that can grow to a monstrous length of about 59 inches (150 cm). Named for the resemblance of its body shape to that of a pike (i.e. the pole-shaped weapon), it hunts in a remarkable way. Able to accelerate at swift speeds, it can remain motionless for long periods of time as it targets unsuspecting prey. This ambush predator’s favorite treats include smaller fish, crayfish, frogs, mice, and snakes.
In Illinois, the northern pike is found in large lake systems with clear waters. It usually remains close to weedy and shallow areas, where it is most likely to visually spot its prey. The most ecologically appealing waterbodies to E. lucius populations are located in the northern parts of the state.
22) Gizzard shad (Dorosoma cepedianum)
The gizzard shad is able to thrive in a wide variety of freshwater systems, particularly those that have a well-defined limnetic zone above deeper and cooler currents. Wherever they are present in dense populations, they take up a large percentage of the fish biomass. In many reservoirs of the Midwest, this species is usually the most abundant fish. Many medium to large-sized piscivores survive by feeding on its schools.
Gizzard shad can easily thrive in many of Illinois’s large rivers, deep lakes, and clean impoundments. In open waters, it feeds on suspended detritus and zooplankton. Soon after its spawning period, collapses in zooplankton densities may be observed. This phenomenon is caused by new shad hatchlings feeding primarily on planktivorous larvae.
23) Burbot (Lota lota)
The sole member of its genus, Lota lota is a fascinating freshwater species that goes by many common names. Anglers refer to it as lingcod, freshwater cod, eelpout, cusk, and burbot. Only found in cool waters and beneath ice, this fish requires low temperatures to effectively hunt and breed. A determined predator, it is most active during twilight.
Illinois’s burbot populations are only found in Lake Michigan, which has depths that are cool enough to keep them comfortable through summer. As surface waters cool in winter, adults begin to form aggregations in the near-shore shallows. Spawners leave the fertilized eggs in bottom substrates, preferably sand or gravel, where they can incubate for a few months before hatching into fry.
24) Yellow bass (Morone mississippiensis)
Although the yellow bass is strikingly similar to the white bass and striped bass in terms of body shape, general appearance, and size, its silvery-yellow color sets it apart. It also has offsets of its horizontal stripes above its anal fin. Usually found in rivers and lakes with ample vegetation and low turbidity levels, it feeds chiefly on small invertebrates.
The yellow bass is a staple part of the freshwater fish community in the Illinois and Mississippi rivers. Its populations have also seeped into the backwaters and lakes associated with these rivers. Its intentionally stocked individuals may be found in relatively large private ponds and artificial impoundments.
25) Black bullhead (Ameiurus melas)
Like other bullhead cats, the black bullhead is a benthic species with a high tolerance for poor water conditions, warm temperatures, and the presence of toxic pollutants. This gives it an evolutionary edge in waters that are closely associated with industrial developments and runoff. It typically favors shallow depths with high turbidity levels.
As this fish does not need to remain camouflaged to hunt, it rarely remains in vegetated zones of freshwater bodies. It is an opportunistic and nocturnal forager that thrives on a diet of both live and dead snacks. Nonetheless, if food is constantly available throughout the day, it may spread out its peak activity times to daylight hours.
26) Banded pygmy sunfish (Elassoma zonatum)
The banded pygmy sunfish is a relatively small freshwater species. Capable of thriving in slow-moving rivers, ponds, lakes, and streams, it tolerates waters with a high concentration of suspended solids. For this reason, some of its populations are known for persisting in the still conditions of murky swamps.
This sunfish breeds in the wetland regions associated with the Wabash and Mississippi rivers along the borders of Illinois. In other states, the loss of wetlands (due to manmade developments) has been associated with the decline of its native populations. Coontails or similar types of aquatic vegetation, particularly those found in flooded wetlands, are necessary for a successful spawning event.
27) Rainbow trout (Oncorhynchus mykiss)
Intentionally stocked in Illinois’s waters to meet the recreational demands of local anglers, the rainbow trout needs cool water temperatures and large sediments to thrive. The annual rise of water temperatures each summer is one of the major impediments to its survival in the state.
Temperatures above 70˚F (21˚C) can cause entire populations of this species to die back, especially as they are unable to reproduce. The natural reproduction of rainbow trout has yet to be observed in Illinois. Thus, this species needs to be stocked at least twice a year to continuously be available as a sportfish. Around 60 of the state’s freshwater bodies are legally stocked with tens of thousands of rainbow trout in both fall and spring.
28) Freshwater drum (Aplodinotus grunniens)
Named for the grunt-like sound emitted by its spawning males, the freshwater drum is also called the grunter, croaker, gray bass, and sheephead. Deep-bodied and frequently identified by the hump on its back, the intensity of its silvery to bronze coloration is largely determined by the water clarity in its habitat. In clear waterbodies, this species is more likely to develop brown hues as it matures.
Found throughout the state of Illinois, the freshwater drum prefers to remain in deep waters that are devoid of vegetation and rocky cover. As it is a bottom feeder, it thrives on a diet of macroinvertebrates and smaller benthic fish species. During its spring-summer spawning period, it releases its gametes in open water. Without any form of protection from predators, the eggs often hatch into fry that are instantly gobbled up by larger fish!
