Fish Facts: 11 Things You Didn’t Know About Colorado’s Fisheries

With more than 9,000 miles of rivers, 2,000 natural lakes and streams, it's as if Mother Nature had fishing in mind when she created Colorado.
 cutthroat trout
A cutthroat trout. Photo by Kevin Rogers/CPW.

Colorado is truly an angler’s paradise. Home to more than 9,000 miles of rivers, 2,000 natural lakes and hundreds of gin-clear streams, it’s as if Mother Nature had fishing in mind when she created this beautiful state. And with waters generously dispersed from the high mountains all the way to the Eastern Plains, Colorado’s fishing opportunities are as diverse as the Rocky Mountain landscape.

Yet, in spite of the variety of fishable waters and abundance of natural habitat, it’s only because of the dedicated conservation work of Colorado Parks and Wildlife’s (CPW) aquatic biologists and hatchery technicians that Colorado boasts some of the best fishing in the nation.

Whether you’re an avid angler or just someone who enjoys the occasional weekend fishing trip, here are 11 “Fish Facts” that you should know about Colorado’s fisheries: 

1. Aerial Stocking

If you’ve ever fished one of Colorado’s magnificent alpine lakes, you were probably captivated by the postcard scenery and by the beauty of our native cutthroat trout. But, did you know that those remarkable fish were likely stocked there by airplane?

With a fleet of four, single-engine Cessna’s, CPW stocks around 350,000 trout annually into more than 500 backcountry lakes. Each specially modified plane carries nine storage tubes that hold around 2,000 fish and four gallons of water. With a carefully-plotted flight plan, one Cessna can stock as many as nine different waters in a single voyage. The trout, called fingerlings, are less than an inch long, allowing pilots to carry more fish per trip. The reduced mass of the tiny fish also ensures a high survival rate. The dense water that encases the fish takes the brunt of the landing and, amazingly, more than 90 percent of the fingerlings survive their aerial descent.

Using a “bomb” button on the flight yoke, the pilot can drop the fish at just the right location, airspeed and altitude. The ideal drop-zone is approximately 150 feet off the water with an airspeed of around 90 mph. Flying this low and slow in a small plane can be a dangerous undertaking, particularly in Colorado’s high mountains where unpredictable weather and rugged terrain can challenge even the most skilled pilots. As such, most of these missions are flown early in the morning and in late summer/fall when thunderstorms and high winds are less likely.

2. Fish Hatcheries and Stocking Trucks

With so many waters scattered throughout the state, you may have wondered how it’s even possible to keep all of the different locations stocked with fish. To accomplish this ambitious feat, CPW manages 18 different fish hatcheries that raise some 35 species of cold- and warm-water fish. Using a fleet of 80 specially designed pickup and semi trucks, CPW stocks around 90 million fish annually. Each semi truck can carry up to 6,000 pounds of fish. The stocking trucks are one of the most recognizable vehicles on the road, always attracting excited onlookers as they deliver their precious cargo across the state. To see which waters were recently stocked, check out CPW’s weekly fish-stocking reports.

3. Spawn Collection

To ensure that there are enough fish to stock every year, CPW sets up spawn-collection sites at lakes and reservoirs across the state. Here, biologists net spawning fish and then collect roe (eggs) from the females and milt (sperm) from the males. The roe and milt are carefully combined by hand and then the fertilized eggs are transported to state fish hatcheries. CPW collects around 140 million eggs annually. Walleye, kokanee, brown trout and cutthroat trout are just a few of the species that provide eggs each year. The video above, “Panning for Gold,” provides an intimate look at one of CPW’s cutthroat trout spawning operations in southwest Colorado.

4. The Egg Trade

fish eggs
Fish eggs. Photo courtesy of US Army Corps of Engineers. 

In addition to collecting fish eggs for Colorado’s hatcheries, CPW trades both eggs and fish with more than 10 different states, as well as the United States Fish and Wildlife Service (USFWS). Based on supply and demand, CPW works with other state and federal hatcheries to ensure there’s enough of each species to meet angler demand and annual stocking requirements. CPW recently traded walleye eggs and sauger milt to Texas and Kansas and, in return, received 4.5 million wiper fry. The wipers were stocked into Lake Pueblo this spring.

5. Hybrid Vigor

Wipers are one of the most popular hybrid species among Colorado anglers. Photo by Tyler Baskfield/CPW.

6. Native Cutthroat Trout Restoration

 native cutthroat trout
Icy water glazes a native cutthroat trout. Photo by Kevin Rogers/CPW.

Beautiful and vibrant, the native cutthroat trout is a favorite among Colorado anglers. Colorado is home to three subspecies of cutthroat: the Rio Grande, Colorado River and the renowned greenback, which was designated the state fish in 1994. But, despite its iconic stature, the plight of the cutthroat has been both challenging and uncertain. For decades, cutthroat trout populations have declined throughout the western United States. Working with a consortium of state and federal wildlife agencies, Trout Unlimited and other conservation groups, CPW has developed an aggressive conservation strategy to help restore native cutthroat populations. Key components include CPW’s egg-collection, hatchery and stocking programs. Fishery biologists are hopeful that these ambitious efforts will help to establish self-sustaining cutthroat populations throughout Colorado.

7. Never Stop Growing

 state-record grass carp
Carpe diem! Assistant Chief of Hatcheries Jim McKissick weighs and measures the state-record grass carp. Photo by Wayne Lewis/CPW.

Did you know that fish are indiscriminate growers? This means that fish continue to grow throughout their entire life span. In Colorado’s more fertile lakes and reservoirs, fish can grow up to 1 inch per month. To see just how big some species get in Colorado, check out CPW’s State Fishing Records and Master Angler programs. The largest fish ever landed in Colorado, a 58-pound grass carp, was caught in 2013 at Cottonwood Park Lake in Jefferson County.

8. Put and Take

A boy's smile hides behind a rainbow trout at Steamboat Lake State Park
A boy’s smile hides behind a rainbow trout at Steamboat Lake State Park. Photo by Wayne Lewis/CPW.

Despite Colorado’s abundant fish populations, most fish cannot successfully reproduce in the wild. And, of those species that are able to reproduce naturally, recruitment (the number of juvenile fish that actually survive to be added to a population) is too low to support a fishable population. Because of this, CPW manages most of Colorado’s lakes and reservoirs as “put-and-take” fisheries. This means that fish are stocked with the expectation that most anglers will keep their bag and possession limits. Although Colorado has a number of wild trout streams that support self-sustaining populations, the vast majority of the state’s waters are stocked with fish that were raised in hatcheries.

9. Gold Medal Waters

bruiser brown trout
Angler Caryn Feil shows off a bruiser brown trout that she caught at a Gold Medal water.

Gold Medal waters are rivers and lakes that offer anglers exceptional opportunities to catch large trout. CPW’s biologists define Gold Medal waters as any location that produces 60 pounds of trout per acre, and at least 12 14-inch or larger trout per acre. This esteemed designation is given out sparingly to only those waters that provide ideal aquatic habitat and outstanding fishing. In fact, only 322 of Colorado’s 9,000 miles of trout streams and three lakes have achieved Gold Medal status. CPW typically implements special restrictions to manage fishing pressure and to protect the quality of these fisheries. Be sure to check the Colorado Fishing Regulations brochure before fishing any Gold Medal waters.

10. Protecting Native Species

Biologist Mark Haver displays a bonytail chub
CPW Aquatic Biologist Mark Haver displays a bonytail chub at the NASRF. Photo by Theo Smith/CPW.

In addition to stocking fish for recreational angling, CPW’s J. W. Mumma Native Aquatic Species Restoration Facility (NASRF) is dedicated to protecting and restoring threatened and endangered fish species native to Colorado. The state-of-the-art hatchery, located near Alamosa, currently raises 12 species of threatened and endangered fish, including the federally endangered bonytail chub and other state species of concern. Since its inception in 2000, the NASRF has protected 16 different fish species and has stocked more than 2.1 million fish in rivers, streams and lakes throughout Colorado. The NASRF is the only hatchery of its kind in North America.

11. Hunters and Anglers Support Colorado’s Fisheries

Angler and a bull elk share a stream in RMNP
Angler Iolanthe Culjack and a bull elk share a stream in Rocky Mountain National Park. Photo by Jerry Neal/CPW.

Did you know that sportsmen pay for all fishery management in Colorado? Because CPW does not receive general tax dollars to fund its fish hatcheries and conservation programs, these efforts are paid for, almost exclusively, by hunters and anglers through Habitat Stamp purchases and license sales. Proceeds from Great Outdoors Colorado (GOCO) also help to support Colorado’s fishing resources.

To learn more about CPW’s financial sustainability and conservation programs, and to see how you can contribute, visit CPW’s website.

Written by Jerry Neal. Neal is a media specialist for Colorado Parks and Wildlife and is the editor for CPW’s blog, Colorado Outdoors Online. 

4 Responses

      1. Photos are great thanks for the scenery and fish photos. I love to fish. Thanks again!! 😊

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