Fish

Of all the fish species native to the Colorado River Basin, the bonytail experienced the most abrupt decline. Today, it is extremely rare to find.

NPS

Fish populations in the Green and Yampa rivers have undergone significant changes in the last century. Today, more than 50 fish species can be found in these rivers, but fewer than one-third of those are native to the Green and Yampa. Of the 14 native fish species found in the monument, three are endangered and one is threatened. Other native species are in decline.

For a complete list of fish species found in the monument, use the NPS Species tool below.

 

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Species Attribute Definitions

Definitions

Occurrence

Occurrence values are defined below. One or more Occurrence Tags may be associated with each Occurrence value.

Present: Species occurs in park; current, reliable evidence available.

Probably Present: High confidence species occurs in park but current, verified evidence needed.

Unconfirmed: Species is attributed to park but evidence is weak or absent.

Not In Park: Species is not known to occur in park.

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Occurrence Tags

Adjacent: Species is known to occur in areas near to or contiguous with park boundaries.

False Report: Species was reported to occur within the park, but current evidence indicates the report was based on misidentification, a taxonomic concept no longer accepted, or other similar problem of error or interpretation.

Historical: Species' historical occurrence in park is documented. Assigned based on judgment as opposed to determination based on age of the most recent evidence.

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Abundance

Abundant:

• Animals: May be seen daily, in suitable habitat and season, and counted in relatively large numbers.
• Plants: Large number of individuals; wide ecological amplitude or occurring in habitats covering a large portion of the park.

Common:

• Animals: May be seen daily, in suitable habitat and season, but not in large numbers.
• Plants: Large numbers of individuals predictably occurring in commonly encountered habitats but not those covering a large portion of the park.

Uncommon:

• Animals: Likely to be seen monthly in appropriate habitat and season. May be locally common.
• Plants: Few to moderate numbers of individuals; occurring either sporadically in commonly encountered habitats or in uncommon habitats.

Rare:

• Animals: Present, but usually seen only a few times each year.
• Plants: Few individuals, usually restricted to small areas of rare habitat.

Occasional:

• Animals: Occurs in the park at least once every few years, varying in numbers, but not necessarily every year.
• Plants: Abundance variable from year to year (e.g., desert plants).

Unknown: Abundance unknown

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Nativeness

Native: Species naturally occurs in park or region.

Non-native: Species occurs on park lands as a result of deliberate or accidental human activities.

Unknown: Nativeness status is unknown or ambiguous.

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List Differences

The Checklist contains only those species that are designated as "present" or "probably present" in the park.

The Full List includes all the checklist species in addition to species that are unconfirmed, historically detected, or incorrectly reported as being found in the park. The full list also contains species that are "in review" because their status in the park hasn't been fully determined. Additional details about the status of each species is included in the full list.

The checklist will almost always contain fewer species than the full list.

Select a Park:

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Species attribute definitions

Search results will be displayed here.

Visit NPSpecies for more comprehensive information and advanced search capability. Have a suggestion or comment on this list? Let us know.

 

Native Endangered and Threatened Fish

Bonytail (Gila elegans) Endangered
Colorado Pikeminnow (Ptychocheilus lucius) Endangered
Razorback Sucker (Xyrauchen texanus) Endangered
Humpback Chub (Gila cypha) Threatened

 

Bonytail (Gila elegans)

NPS / Dinosaur National Monument

Bonytail (Gila elegans)
Endangered
This the rarest of the endangered native fish of the Colorado River Basin. Following the construction of the Hoover dam, bonytail quickly disappeared from the lower Colorado River Basin. The bonytail is a member of the chub group of minnows. It's species name, elegans, refers to the elegant manner in which the fish swims. They have large eyes and body that tapers to a pencil-thin point just before its tail. They can reach lengths of up to 22 inches (56 cm) long.

 

Colorado Pikeminnow (Ptychocheilus lucius)

NPS / Dinosaur National Monument

Colorado Pikeminnow (Ptychocheilus lucius)
Endangered
This is the largest minnow in North America. Historical accounts record pikeminnows up to 6 feet (2 meters) long and up to 80 lbs (36 kg). In the early 1900s, the Colorado pikeminnow was the top fish predator in the Colorado River Basin. It was considered an easily-caught "sport" fish. They're known for long-distance spawning migrations of up to 200 miles (322 km). Dinosaur preserves some important spawning bars for pikeminnow.

 

Razorback Sucker (Xyrauchen texanus) 

NPS / Dinosaur National Monument

Razorback Sucker (Xyrauchen texanus)
Endangered
This is one of the largest suckers in North America, and the only remaining member of the genus, Xyrauchen. Historically, they were widespread and abundant throughout the Colorado River Basin, but their population has declined. The Green River within and around the monument preserves important spawning bars, habitat for juveniles, and overwintering areas for adults. They can grow up to 3 feet (1 meter) long and live for over 40 years.

 

Humpback Chub (Gila cypha)

NPS / Dinosaur National Monument

Humpback Chub (Gila cypha)
Threatened
Like the Colorado pikeminnow and bonytail, the humpback chub is a member of the minnow family. It is easily recognized by the pronounced hump behind its head. It also appears to have an overbite. While the humpback chub was downlisted to a "threatened" species in 2021, this fish is still rare in Dinosaur National Monument. However, larger populations are known to exist in the Desolation and Gray canyons of the Green River.

 

Flaming Gorge Dam

U.S. Bureau of Reclamation

History & Conservation

Historic Green and Yampa Rivers
Fish native to the Green and Yampa evolved in natural-flowing rivers. High spring flows fed by snow melt brought in dirt, silt, and other sediments from the surrounding countryside, making the rivers naturally cloudy. Water temperatures could range from near freezing in winter to almost 70°F (21°C) in summer. Native species were well-adapted to these natural conditions, and thrived in them.

The Green River After Flaming Gorge Dam

In 1962, with the construction of the Flaming Gorge Dam, these conditions largely disappeared from the Green River. Spring flows, temperature fluctuation, and turbitity (the cloudiness of the water) were all reduced. The Green River downstream from the dam became a much clearer, cooler, and calmer river. These changes reduced the number and distribution of several native fish, all of whom were adapted to the rugged conditons of the undammed Green River. Many of these changes in the river system also created more favorable conditions for non-native fishes. Today, three species native to the Green and Yampa rivers are listed as endangered: the razorback sucker (Xyrauchen texanus), Colorado pikeminnow (Ptychocheilus lucius), and bonytail (Gila elegans). The humpback chub (Gila cypha) was removed from the endangered species list and reclassified as threatened in 2021.

 

Smallmouth bass (Micropterus dolomieu) at Buffalo National River in Arkansas. This species is non-native to the Green and Yampa Rivers, and is illegal to re-release in Utah.

NPS / R. Stokes

Nonnative Fish
Even before Flaming Gorge Dam, human activity had begun to affect fish populations in the Green and Yampa rivers. Over the last century, a number of species have been added to the Upper Colorado River Basin. Some of these non-native fish were introduced by state and federal agencies to meet sportfishing demand that existed at the time. Other species were unintentionally introduced when they escaped from ponds and reservoirs into the river system. Non-native fishes, now common in the Green and Yampa rivers, compete for resources including food, space, cover, and phsycial habitat. Some are known to prey on native fishes.

 

This sandbar on the Yampa River serves as vital spawning ground for endangered razorback suckers.

NPS / Dinosaur National Monument

The Yampa River's Role in Conservation
The Yampa River is the largest unregulated tributary remaining in the Colorado River system. As such, it as played a vital role in sustaining native fish species. Thanks to the Yampa's near-natural annual flows, Dinosaur National Monument provides some of the last known spawning and nursery habitat for several of these big river species. Because its naturalistic flow mitigates the effects of Flaming Gorge Dam, the Yampa River improves the ecological integrity of the Green River after the two rivers join at Echo Park.

 

Endangered Fish Recovery Program

The National Park Service is a partner in the Upper Colorado River Endangered Fish Recovery Program, a multi-stakeholder effort to recover the four endangered fish species while allowing water development to continue. Learn more about the endangered fish and the recovery program at the Colorado River Recovery website.