Of the 55 species of native fish in Colorado, there are four notably large endemic fish species. They are peculiar-looking fishes known to live exceptionally long lives. Due to their size, they live in large waterways and prefer various habitats, ranging from the main channel to backwaters and floodplains. Not only are they known for their enormous size, but they are threatened or endangered species on both state and federal levels. If you accidentally catch one of them, it must be returned unharmed to the water because it is considered illegal to catch any of these protected species. Join us to discover the four largest fish in the Colorado River.
Humpback chub (Gila cypha)
The humpback chub is a big, odd-looking fish originally found in the fast waters of the Colorado River system in the United States. Its name was derived from the prominent hump between the head and dorsal fin, which is thought to help this species direct the flow of water and maintain body position in the swift currents of the Colorado River. These fish have recorded lengths of about 1.2 feet (38cm) to 20 inches (50.8cm), making them one of the largest known fish in the Colorado River. For identification, look out for its back which is a light olive-gray coloration with a white belly and silver on the sides. The body of the humpback chub is almost entirely scaleless. Feeding at all levels from the bottom to the surface of the river, it mostly eats invertebrates and, sometimes, other fish. Typically found in Yampa River Canyon and Black Rocks Canyon of the Colorado River, the humpback chub’s population in the Colorado River has been reduced dramatically over the years. It is federally protected and listed as an endangered species in the IUCN red list. The fish’s status as an endangered species has been attributed to habitat loss, especially due to the construction of Glen Canyon Dam.
Razorback sucker (Xyrauchen texanus)
Another large fish in the Colorado River is the razorback sucker, which used to inhabit much of the Colorado River Basin. Adult razorback suckers grow up to an average length of 1.6 ft (50 cm), and some may even grow to reach 3 feet (91cm) in length and weigh about 6 kg or 15 pounds (13.2 lb). The large fish has an olivaceous to brown-black color dorsally and a lighter yellow below. Razorback suckers are easily distinguishable from other suckers by the predorsal keel (or sharp-edged bulge) on the anterior part of their back, between the head and dorsal fin – giving rise to its name. Razorback suckers can live as long as 40 years. This species has also suffered great population declines due to river damming, commercial fishing, predation by non-native fishes, and habitat loss. Found in the Colorado Rivers, Upper Green, and Yampa. Also a threatened species, its range is now limited to the Colorado River upstream of the Grand Canyon and to four reservoirs; Lake Mohave, Lake Mead, Lake Powell, and Lake Havasu. The razorback sucker has been a federally protected fish since 1991, and it is rated as “critically endangered” by the IUCN.
Bonytail chub (Gila elegans)
A freshwater fish native to the Colorado River basin, the bonytail chub is a big fish that grows up to approximately 22 inches to 2 ft (62 cm) long. Like many other desert fishes, its coloration appears dark dorsally and lighter ventrally, serving as camouflage. However, in very clear waters, it looks almost entirely black. They have a long, thin bony tail that tapers down distinctly from their larger body – from which their name was derived. Adult bonytail chubs feed mostly on small fish, plant debris, algae, and terrestrial insects, whereas the young primarily eat aquatic plants. Bonytail chubs have a long life span and can survive up to 50 years. Once abundant and widespread in the basin, it is now the rarest of the endemic big-river fishes of the Colorado River. The numbers and range of bonytail chub species have declined to the point where it has been listed as endangered. In fact, a self-sustaining wild population no longer exists, meaning the species is functionally extinct. Biologists are working on restoring the population in the Upper Colorado River Basin.
Colorado pikeminnow (Ptychocheilus lucius)
Native to the Colorado River Basin of the southwestern United States and adjacent to Mexico, the Colorado pikeminnow is the largest cyprinid fish in North America and one of the largest in the world. With reports of individuals growing up to 6 ft (1.8 m) long and weighing over 80 pounds (36 kg), no other fish in the Colorado River comes close! Like other species of pikeminnows, it has an elongated body, and its head is also elongated, cone-shaped, and flattened, forming nearly a quarter of its body length. The Colorado pikeminnow feeds on species like the humpback chub and other smaller fish species found throughout the basin. An interesting thing about this species is that they travel long distances for their spawning runs (sometimes more than 200 miles). Also called ‘squawfish’ or ‘white salmon’ by early settlers, they have been known to live up to 40 years. Pikeminnows are typically found in Colorado, Upper Green, Yampa, Gunnison, Dolores, San Juan, and White Rivers. This species used to be abundant and widespread in the Colorado basin but is currently listed as ‘Vulnerable’ by the IUCN. The Colorado pikeminnow’s population has declined to the point where it has been eradicated from the Mexican part of its range. It was listed as endangered in the US in 1967 – a fate shared by the three other big-bodied Colorado Basin endemic fish species: humpback chub, bonytail chub, and razorback sucker.
