Nicknamed “Colorful Colorado” because of its enchantingly diverse landscape, the Centennial State is chock-full of natural wonders. With expansive canyons, towering rock formations, vast cave systems, and breathtaking mountain ranges, this landlocked state is a haven for both wildlife and people. Of course, among its many terrestrial attractions, the varied landscape is shaped and enlivened by freshwater ecosystems.
Colorado is home to 200,000+ acres of pristine lakes and ponds. Many of these are drained into by stretches of mountain rivers, which collectively cover a total distance of about 90,000 miles. The bulk of spring-sourced fresh water originates from alpine environments, from which it streams downward, through plains and deserts, before meeting the river systems of neighboring states.
Local bodies of freshwater form unique wetland habitats that support the lives of both native and naturalized flora and fauna. While mining and overfishing have caused declines in the local populations of some native fish, many continue to thrive or are in recovery thanks to conservation efforts. Some of the most important sport fishing targets, forage fish, stocked species, and endemic fish are listed below.
Colorado Freshwater Fish Species
1) Cutthroat trout (Oncorhynchus clarkii)
Considered one of the most beautiful freshwater fish species by both seasoned and inexperienced anglers, the cutthroat trout is extremely popular as a gamefish. Distinguished by one or more red streaks along its lower jaws, this species has several geographically distinct populations, some of which are only found in the Rockies.
Colorado contains three official subspecies of O. clarkii. These include the greenback cutthroat (O. c. stomias), Colorado River cutthroat (O. c. pleuriticus), and Rio Grande cutthroat (O. c. virginalis). The first, which is officially listed as a threatened subspecies, is Colorado’s official state fish. It is largely restricted to the river systems along the eastern regions of the Rocky Mountains.
2) Rainbow trout (Oncorhynchus mykiss)
Now fairly common in Colorado’s mountain streams, lakes, and reservoirs, this eye-catching fish is one of the most frequently-fished species in the state. To meet demand from local anglers, it is regularly stocked into publicly shared freshwater systems. Not native to state waters, it was first introduced in the 1800s. It has since then become a dominant species in several river basins.
In the Rockies, rainbow trout begins to spawn in early spring. Its reproductive populations unfortunately threaten the survival of some endemic subpopulations of fish. Capable of growing faster than many other species in its family, this remarkably competitive trout can weigh as much as 20 pounds (9 kg) in adulthood. The state’s record specimen, which weighed 19 pounds (8.6 kg), was caught in Morrow Point Reservoir.
3) Kokanee salmon (Oncorhynchus nerka)
The landlocked or non-anadromous form of sockeye salmon, kokanee salmon are able to live out their entire life cycle in freshwater systems. This form likely separated from its ancestral, sea-going populations as far back as 15,000 years ago. Though they are not a native species of Colorado, they now have populations that spawn and thrive in several local lake systems and reservoirs.
Kokanee salmon typically grow to about 12 inches (30 cm) long, though they can easily surpass this length in optimal conditions. Their maximum size in local lakes is largely a function of population density and food availability, especially as their main food source is plankton. Their anadromous conspecifics, which can access more productive bodies of water, grow much larger on average. Regardless of their life history, all mature kokanees develop their distinctive red coloration prior to spawning.
4) Mountain whitefish (Prosopium williamsoni)
In Colorado, populations of this native fish can be found in the White, Roaring Fork, Yampa, and Cache la Poudre Rivers. It is indigenous only to the White and Yampa rivers, from which collected specimens were introduced elsewhere. Today, this freshwater species is notably common and is widely distributed throughout its native range.
The overall body shape of the mountain whitefish has a stark resemblance to that of carp and minnows. It has an even, silvery to subtly green coloration. Able to live up to 9 years in the wild, this fish feeds close to or along the benthos of cool streams, pools, and lakes. Its favorite prey types are macroinvertebrates, such as amphipods, crayfish, and mollusks.
5) Brown trout (Salmo trutta)
This non-native fish now has stable and self-replenishing populations through many of North America’s freshwater systems. It has landlocked subpopulations that come in the form of exclusively riverine or lacustrine ecotypes. In Colorado, where it was first introduced in the 1900s, it is now a well-established species. Healthy brown trout specimens occur almost all throughout local stream systems with elevations of at least 6,000 feet (1,800 meters).
A rich source of protein and a highly sought-after sportfish due to its energetic nature, the brown trout can grow to trophy sizes whenever its favored prey types are available. The state’s record catch for this species weighed 30 pounds and 8 ounces (13.8 kg)! Anglers suspect that this monster fish, which was caught close to a hatchery near Almont, likely swam upwards from the Blue Mesa Reservoir.
6) Lake trout (Salvelinus namaycush)
Considered the largest of all freshwater chars, the lake trout can weigh as much as 102 pounds (46 kg) and grow to about 50 inches (127 cm) long! This enormous fish has been heavily introduced into freshwater systems throughout the continent. It first made its appearance in Colorado in the 1890s. The state now has self-sustaining populations that regularly spawn in fall.
Like its close cousins, this trout tends to favor conditions in large reservoirs and lakes. The state record, which weighed 50.3 pounds (22.8 kg), was caught in Blue Mesa in 2017. Healthy individuals in productive systems can supposedly live for up to 20 – 60 years. They are late to mature, however, and are highly sensitive to acidification and overfishing.
7) Brook trout (Salvelinus fontinalis)
A remarkably prolific fish, the brook trout tends to outcompete its close cousins when it comes to spawning rates and successful reproduction. Also called squaretail, brook charr, and coaster trout, this fish favors cool and clear waters in productive streams and ponds. In freshwater bodies co-dominated by lake trout, brown trout, and arctic char, it can easily hybridize with its cousins.
Colorado’s largest-ever recorded brook trout was recently fished in Monarch Lake. This enormous brookie weighed 7.84 pounds (3.6 kg) and measured 23.25 inches (59 cm) long. It was beautifully and evenly dark in color and was generously speckled with a constellation of white-yellow spots. Ideal places to fish for more record-breaking specimens include beaver ponds, streams, and mountain lakes.
8) Green sunfish (Lepomis cyanellus)
This panfish is found in large expanses of wetlands stretching from the western Rocky Mountains to the eastern stretch of Appalachia. Outside of its indigenous range, its populations can easily become invasive due to their tolerance to pollution and their high fecundity rate. This fish can rapidly occupy gravelly or sandy lakes, ponds, and slow-moving backwaters in the absence of voracious predators.
Green sunfish tend to gravitate toward relatively shallow habitats with vertical cover. As omnivores, they feed on vegetation, insect larvae, snails, and pretty much anything organic that falls into the water and can fit into their small mouths. Named for their bluish-green coloration, they can easily be mistaken for their close cousin, the bluegill (L. macrochirus).
9) Orangespotted sunfish (Lepomis humilis)
The orangespotted sunfish has a competitive edge in poorly oxygenated waters. In the absence of predators, their tolerance for low dissolved oxygen allows them to quickly establish communities in shallow, slow-moving pools. Compared to other types of sunfish, this species is more likely to be found in Colorado’s turbid backwaters. They slowly expand their local distribution by venturing into these systems and forming new aggregations.
Able to grow up to 6 inches (15 cm) long, this attractive panfish can live for about 4 – 7 years on average. It is best searched for in June to July, when it moves closer to the shoreline to spawn. Its nesting areas tend to be close to those of other sunfish, increasing the chances of interspecies hybridization.
10) Black bullhead (Ameiurus melas)
A scaleless catfish, the black bullhead is distinguished by the presence of an adipose fin, the truncated shape of its tailfin, its deep-black barbels, and lighter pigmentation close to the base of its tail. Its ventral region is several degrees lighter than its black-to-brown dorsal region. Adults, which maintain a nocturnal feeding habit, can grow to a maximum length of about 24 inches (61 cm).
The black bullhead remains close to the substrate, above which it maintains a varied diet of aquatic insects, small crustaceans, small fish, fish eggs, and, occasionally, plants. In Colorado, its populations tend to be most successful in shallow and slow-moving streams and lakes, where it can tolerate suboptimal conditions. Its presence in these environments threatens humpback chub (Gila cypha) populations.
11) Colorado pikeminnow (Ptychocheilus lucius)
This warm-water fish is one of the largest minnows in all of North America. Its range was once fairly widespread, extending into neighboring states and further south into northern Mexico. Today, due to habitat conversion and the construction of dams, its extant populations are limited to the upper reaches of the Colorado drainage basin.
Once known as Colorado squawfish, this increasingly rare species favors channels and eddies with rich communities of its favored prey items – smaller minnows and suckers. Its young favor turbulent shorelines, where they feed on insect larvae and small crustaceans. Able to grow up to 6.5 feet (2 meters) long, this impressively-sized fish is officially listed as a vulnerable species (IUCN).
12) Razorback sucker (Xyrauchen texanus)
A member of the Catostomidae family, the razorback sucker is another species with an increasingly limited natural range. It was once found all throughout the Colorado River Basin. Today, its populations have unfortunately been reduced due to decades of habitat loss. As spawning adults are found in just a few sites, this species is now endangered and has been placed under federal protection.
The razorback sucker has a peculiar appearance. Along the anterior part of its dorsal region is a notably sharp-edged humpback. This feature is distinct enough to make this species unmistakable. Of course, it is even more prominent in larger individuals, which can measure up to 3 feet (0.9 meters) long! However, even in protected parts of its range, this long-lived fish rarely grows to more than 1.5 feet (46 cm).
13) Channel catfish (Ictalurus punctatus)
The hardy channel cat is one of the most widespread and economically important species throughout its native range. Targeted by anglers and cultured in dedicated farms in several states, it is a prolific omnivore with a knack for thriving in polluted waterbodies. This bony fish, which can easily weigh as much as 40 – 50 pounds (18 – 23 kg) at maturity, is comfortable in muddy to clear rivers, reservoirs, ponds, and lakes.
Spawning channel cats are known for digging nests, into which they release their eggs. In the freshwater systems that they dominate, the substrate can thus appear pockmarked. Mature specimens naturally remain close to the benthos as they can feed on other bottom-feeding fish and their prey items. In Colorado, giant channel cats are known for having thriving populations in many reservoirs.
14) Humpback chub (Gila cypha)
Like the razorback sucker, with which it shares a native range, the humpback chub has a prominent bulge along the anterior part of its dorsal region. Compared to that of the former, this species’ hump has a more oblique or less sharp curvature. It is also much smaller on average because it grows to a maximum length of just 20 inches (51 cm) at maturity. This species’ unique shape is believed to help it retain a pelagic position in the swift currents of the Colorado River.
Currently listed as an endangered species, the humpback chub favors the highly oxygenated water conditions of the most rugged and remote canyons. With individual specimens numbering in the low thousands, it has a few isolated groups that continue to persist. These are threatened by both natural factors and anthropogenic disturbances, such as water pollution and the introduction of non-native species.
15) Largemouth bass (Micropterus salmoides)
Known for being a voracious carnivore wherever it is found, the largemouth bass is a fantastic food and sport fish. Set apart by the impressive size of its gape, it is capable of eating a wide range of prey types. Although it favors forage fish, such as panfish and minnows, its largest specimens can consume its nonconventional fare, such as smaller reptiles, amphibians, and even waterfowl.
This species was introduced into Colorado’s waters in the 1870s. Since then, it has prospered and is now present in several self-sustaining populations in many of the state’s major river and lake systems. Note, however, that trophy bass sizes are not as common in the state as they are in this species’ native waters. Regardless, decent catches are regularly reported from reservoirs and ponds in western and eastern Colorado.
16) Northern pike (Esox lucius)
Northern pike is known for being a fantastic sport fish as it can grow to an impressive size and put up a memorable fight on the line. These aggressive, fresh to brackish water fish are set apart by their compressed and lengthy body shape. Anglers can easily spot them through the surface of clear water bodies due to their yellow speckles and bars, which contrast their olive-green coloration.
Colorado’s record catch for northern pike was a 30-pound, 11-ounce (14 kg) fish caught in Stagecoach State Park. Pike fishing opportunities are not hard to come by, especially as this fish has become naturalized in most major water systems. As it is a non-indigenous species in the state, it can be fished without daily catch limits.
17) Bonytail chub (Gila elegans)
Closely related to the humpback chub, with which it shares a critically endangered profile, the bonytail chub is one of Colorado’s indigenous freshwater species. Among all of the Colorado River’s large cyprinids, it is the most difficult to find. Its increasingly rare occurrence hinges on the release of hatchery-reared specimens. Wild populations are unfortunately considered “functionally extinct.”
The bonytail chub was once abundant in the warm backwaters and large tributaries of the Colorado River. Its distribution stretched further south into the southwestern states and northern Mexico. The construction of dams and the introduction of non-native fauna have greatly imperiled its natural populations.
18) Bluegill (Lepomis macrochirus)
One of the most popular and ecologically important species of panfish wherever it is found, the bluegill plays several important roles in the food web of freshwater systems. As a small to medium-sized perciform, it serves as a primary or secondary consumer. Its mature, omnivorous specimens are able to consume small fish and practically anything they can fit into their mouths. Juveniles feed on water fleas, rotifers, and small crustaceans.
Thriving populations of predatory species are necessary for maintaining the quality of bluegill populations. Bluegills form the backbone of many native species’ carnivorous diets. If their populations aren’t frequently foraged, they can quickly overpopulate enclosed systems. This prolific game and food fish tends to spawn all throughout summer and can exhibit stunted growth in high densities.
19) American gizzard shad (Dorosoma cepedianum)
The American gizzard shad plays a dominant role in many freshwater systems due to its heavy consumption of zooplankton and phytoplankton communities. Once its specimens reach a moderate size, they become a choice forage food for larger game fish. Adults can measure up to 18 inches (45.7 cm) long in cool, productive waters. The largest populations are found in calm lakes and reservoirs, though hardy individuals may also persist in rivers and streams.
In Colorado, gizzard shad is largely restricted to the reservoirs and river systems associated with South Platte and the Arkansas drainage. There, the most prolific adults spawn in a wide range of habitats with mild to warm water temperatures.
20) Mottled sculpin (Cottus bairdii)
Named for its uneven distribution of speckles and yellowish-brown bars, the mottled sculpin favors the relatively clear and highly oxygenated riffle areas of streams and rivers. In these cool zones of freely-flowing water, it feeds on aquatic macroinvertebrates. Its favorite prey items are insect larvae that feed on organic materials settling on bottom substrates.
A non-native fish in Colorado’s waters, the mottled sculpin was accidentally introduced into the state by Colorado’s own wildlife division. The exact distribution of sculpins in the area remains to be documented. Distinguished by its large pectoral fins, which allow it to prop up its head, this fish grows to a maximum length of just 6 inches (15 cm).
21) Common shiner (Luxilus cornutus)
The common shiner favors clear, highly-oxygenated conditions in pools, streams, and rivers. It can also be found in the shallow shorelines of ponds and lakes with temperatures that remain fairly mild throughout the year. In its microhabitats (e.g. riffle zones, rocky pools), it feeds on vegetation, small aquatic insects, and juvenile fish. Healthy adults rarely measure more than 6 inches (15 cm) long.
As suggested by its common name, the shiner is covered in silvery scales that glimmer under bright light. Sexually mature males are set apart by a light pink tinge over their bodies and fins. Breeding tubercles also appear on their heads prior to spawning.
22) Fathead minnow (Pimephales promelas)
The fathead minnow is another small fish with immense ecological value. Based on its feeding habits, it can be characterized as a filter feeder and an omnivore. To find food, it sifts through bottom substrates and through small particles found on the benthos. In more productive habitats, it feeds on bits of vegetation, zooplankton, and tiny macroinvertebrates.
Heavily introduced into many freshwater systems via its use as bait fish, this feeder fish is quite effective as a lure for larger game species. Its appeal as a forage fish in private bass ponds has also played a hand in its seemingly all-encompassing distribution. This stout yet small fish has definitely helped shape Colorado’s freshwater systems as it may very well be present in almost all of the state’s drainage systems.
