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Fish Species Identification
Fish Species Identification

​​​​​​​​Rainbow Trout ​​

Rainbow Trout, © Joseph R. Tomelleri  ​

These fish were introduced in the 1880s and have become both the angler’s favorite and the mainstay of Colorado’s hatchery system (millions of catchable and subcatchable sized fish are stocked annually). Rainbows can be found in most mountain lakes and streams, as well as many plains reservoirs. Physical characteristics that can help distinguish rainbow trout include dark spots on a light body, continuous spotting throughout the body, and often a “rainbow” horizontal reddish stripe. Rainbow trout may be caught with a variety of flies, baits, and lures.
Cutthroat (Native) Trout

Cutthroat Trout  © Joseph R. Tomelleri

Several subspecies of cutthroat trout are found in Colorado, of which three are native – the gree​​​nback, the Rio Grande and the Colorado. The range of these fish has decreased due to a variety of habitat factors, and extensive recovery efforts are underway by the Colorado Parks and Wildlife. Cutthroat trout can be distinguished from rainbows by heavier spotting toward the tail and the presence of a red slash on their “throat.” Anglers may find these trout in high lakes and streams.
Brown Trout

Brown Trout © Joseph R. Tomelleri 

The brown trout was first brought into this state in the 1890s and is now abundant from high mountain streams to broad rivers flowing onto the plains. These fish can be difficult to catch, but many anglers have good success during their fall spawning runs. A large dark spotting pattern and reddish dots can help anglers distinguish these fish from rainbows and cutthroats.
Brook Trout

Brook Trout © Joseph R. Tomelleri 

An entry to Colorado in the late 1800s, the brook trout feeds on aquatic and terrestrial insects and will rise to a large range of small lures, baits and flies. Brook trout have white spots (worm-shaped on top) on a dark background with tri-colored outlined fins (orange, black and white). This prolific fish often becomes overpopulated and can out-compete other trout. They are typically found in higher elevation lakes, beaver dams and streams.
Lake Trout

Lake Trout © Joseph R. Tomelleri 

Lake trout, also known as Mackinaw, are the largest trout in North America. Mackinaws have white spots on a dark background with a deep fork in their tail. As the name suggests, these fish are found in mountain lakes and are usually in deeper water. Anglers also enjoy success with this species during the fall and spring in shallower areas and when ice-fishing.
Kokanee Salmon

Kokanee Salmon © Joseph R. Tomelleri 

Kokanee (land-locked Pacific sockeye salmon) are suited to the large, fluctuating mountain reservoirs of Colorado. These silver fish with black spots on the upper half of their bodies can be found  swimming in compact schools feeding on zooplankton, a food source unaffected by the drawing down of reservoirs. They turn reddish in color and males develop a “hook jaw” during the fall spawning season. Trolling with cowbells at medium depths provides angling success. Special snagging seasons are offered on some areas during spawning runs, and provide much of the catch for these delicious salmon. Kokanee die after spawning.
Mountain Whitefish

Mountain Whitefish © Joseph R. Tomelleri 

A native to Colorado in the Yampa and White rivers, whitefish have also been introduced in the Colorado River and Cache la Poudre drainages. These fish have larger scales than trout and still possess an adipose fin (small flap of skin on their back toward the tail). A weak mouth means delicate hooking and handling is required to land this fish. Smoked whitefish are considered a delicacy in many parts of the country.

Splake © Joseph R. Tomelleri 

Splake are a hybrid species of lake and brook trout with the best features of both fish. They can be difficult to distinguish as they hold characteristics from both parents. Splake have tri-colored pelvic fins like brook trout and their tails are slightly forked. Splake are found in high mountains lakes and have been used since the 1980s to thin out stunted brook trout populations. Anglers relish their large sizes (up to 18 pounds) and find success with flies, lures and bait during the summer.

Grayling © Joseph R. Tomelleri 

These arctic imports provide some additional excitement to mountainous lakes. A large sail-like dorsal fin extending over their silver bodies make them easy to identify. Grayling have extremely small mouths and can usually only be caught on small flies or lures. Even though grayling are relatively small in stature (usually less then 12 inches), they can be a nice challenge to anglers, not to mention a great photo opportunity.

Wiper © Joseph R. Tomelleri 

Introduced into eastern Colorado lakes in the early 1980s, this fish is a hybrid between white bass and striped bass. Wiper have become a very popular sportfish because of their hard fighting. Wiper are a schooling fish that can be found “busting” prey fish on the surface during the summer. Casting shad imitations or various lures at the “busting” prey and holding on tight is a fun method for catching wiper. Trolling can also be effective.

Walleye © Joseph R. Tomelleri 

Since their introduction in 1949, walleye have been placed in most large warm- and cool-water reservoirs. You can identify walleye by looking for their two separate dorsal fins and a white tipped tail. Adults feed entirely on other fish and are most often caught by slowly cranking jigs and spinners over bottom structures. Walleye are one of Colorado’s tastiest fish and they have been caught in excess of 18 pounds.

Saugeye © Joseph R. Tomelleri 

This hybrid of walleye and sauger has been stocked into reservoirs throughout the eastern plains of Colorado since the 1980s. Saugeye can be distinguished from walleyes by black mottling marks on their bodies, tails that do not have a white tip and black pigmentation in between dorsal spines. Saugeye don’t grow as big as walleye, but are just as tasty. Anglers have luck catching saugeye by trolling live bait or slowly retrieving jigs over bottom humps and points.
Yellow Perch

Yellow Perch © Joseph R. Tomelleri 

Another long ago introduced species, the yellow perch may be Colorado’s most abundant game fish and one of the most table worthy. Yellow perch have two separate dorsal fins with large vertical dark stripes on their yellowish sides. These fish can be found in large schools and are caught by using bait or small spinners. Yellow perch are usually less than one pound, but can be found over two pounds in some waters.
Channel Catfish

Channel Catfish © Joseph R. Tomelleri 

Channel cats are native to eastern Colorado and have been stocked in warmer rivers and reservoirs throughout the state. These fish are easily identified by their barbels (whiskers), forked tail and sporadic black spotting. Night fishing with live bait, chicken innards, flavored dough balls, or any other smelly concoction provides the best angling success. Cats larger than 30 pounds have been caught in Colorado, and for those willing to take the effort, they make a tasty dinner.
Smallmouth Bass

Smallmouth Bass © Joseph R. Tomelleri 

Introduced to Colorado in 1951, small-mouth have been stocked in warm- and cool-water reservoirs and lakes in many parts of the state. The best way to distinguish the smallmouth from its cousin, the largemouth bass, is by the “smallies” jaws that does not extend beyond the eye. They maintain broken vertical lines on their sides and many have a reddish eye. Smallies are frequently caught along rip-rap shorelines with small jigs or crayfish imitations, and can be a great fish for impatient kids who may need a lot of action.
Largemouth Bass

Largemouth Bass © Joseph R. Tomelleri 

Among the first species of fish introduced into Colorado was the largemouth bass in 1878. As the name suggests this fish has a very big mouth and its jaw extends past the eye. You can also distinguish them as the bass with the horizontal stripe on their body. Largemouth have exceeded 10 pounds in Colorado and are renowned for their aggressive predatory behavior. Casting lures and plugs during dawn and dusk hours around cattails and sunken logs will give you the best chance to land one of the lunkers.
Tiger Muskie

Tiger Muskie © Joseph R. Tomelleri  
The tiger muskie is a hybrid of northern pike and muskie. These fish were introduced into Colorado in the 1980s for the purpose of biologically controlling suckers and carp and providing a trophy-sized fish .The biggest fish ever caught in Colorado was a tiger muskie. Their long snout filled with teeth and dark tiger striped sides on a light body make them easy to identify. Many anglers relish the trophy fishing opportunities provided by these denizens of the deep, that in Colorado may reach over 40 pounds. The best opportunity to catch a tiger muskie would be by throwing large lures over vegetation during the summer. Northern pike look like tiger muskie, but have whitish irregular chain markings on a dark body.
Black Crappie

Black Crappie © Joseph R. Tomelleri 

Introduced in 1882, crappie are now abundant in eastern Colorado waters. Crappie are a pan-shaped fish with black splotches on a silver background, whose dorsal spines and rays get longer as they approach the tail. Crappie are a schooling fish that often congregate around vertical structures. Anglers have the most success for crappies jigging by structure in the early spring. Typically, crappie weigh 1/2 to 3/4 pounds, but specimens in excess of four pounds have been caught.

Blue Gill  © Joseph R. Tomelleri 

This sunfish has a short and deep body. As with all sunfish, the dorsal (top) fin is not split. The bluegill has a small mouth on a short head and a dark gill flap with no trim. There are parallel vertical bars on the side with long, pointed pectoral (side) fins. A male bluegill in breeding colors has brilliant blue fins and a red-orange stomach. The female bluegill is dark on the back with vertical stripes on the body. Bluegills are best caught in the morning or evening using small tackle ranging from a bobber and worm to delicate dry flies. Once one bluegill is located, others will be nearby. Bluegill spawn in colonies from late spring to August, building nests on gravel, sand, mud, leaves, or sticks in 1-4 feet of water. As summer heat becomes extreme, these fish move to deeper water and the shade of weed beds.
Green Sunfish

Green Sunfish © Joseph R. Tomelleri 

This fish is similar in appearance to the bluegill, but has a larger mouth and is olive in color with short, rounded pectoral fins and yellow trim on the fins. This stocky fish is found in both streams and impoundments and spawns in shallow areas from June to mid-August. Like most sunfish, this sporty panfish can be taken with crickets, worms, and other bait rigged under a bobber, or with small lures, jigs, and flies.

Protected Fish i​​n Colorado

Shown here are three specie​​s of fish that anglers might possibly catch if fishing in the Colorado River drainage. If caught, the fish should be returned to the water unharmed as quickly as possible. Other protected fish in Colorado are the greenback cutthroat trout, the bonytail chub and the Arkansas darter.

Colorado Pikeminnow Colorado Pikeminnow © Joseph R. Tomelleri

Humpback Chub Humpback Chub © Joseph R. Tomelleri

Razorback Sucker Razorback Sucker © Joseph R. Tomelleri

All fish illustrations on this page by © Joseph R. Tomelleri