The Rare Native Fishes of the Colorado River Basin

 

The four ESA listed species represent more than a quarter of all native species in the Colorado River basin and are essential indicators of ecosystem health. All Colorado River fishes evolved 3-5 million years ago in flashy, desert rivers.

If you encounter any of these fish please return them unharmed to the river.

U.S. Fish and Wildlife Service  biologist holds captured endangered bonytail

Bonytail (Gila elegans)
Bonytail is the rarest of the native fish of the Colorado River, with large fins and a streamlined body that is pencil-thin near its tail. Bonytail are members of the “chub” group of minnows and typically have gray or olive-colored backs, silver sides, and white bellies.

Bonytail can grow to 22 inches or more and have been known to live up to 50 years. As the rarest of the four species, little is known about what environmental conditions bonytail prefer. Recent findings indicate that they may need similar habitats to razorback sucker to reproduce: floodplain wetlands separated from the river or muddy inflows of large reservoirs. Bonytail are thought to spawn at 2 to 3 years of age during late June and early July and eat insects, plankton, and plant matter.

Colorado pikeminnow (Ptychocheilus lucius)
The Colorado pikeminnow is the largest minnow in North America. Called the “white salmon” by early settlers, the Colorado pikeminnow has a torpedo-shaped body which allows for long migrations of more than 200 miles in late spring and early summer to reach spawning grounds.

Colorado pikeminnow can live as long as 40 years and were historically known to grow to nearly 6 feet long and weigh 80 pounds. Today, researchers see adult Colorado pikeminnow up to 4 feet in length. Young Colorado pikeminnow feed on insects and plankton, whereas adults feed mostly on fish.

The Colorado pikeminnow was a valued food source by early settlers. It is the only native predator in the Colorado River basin and has been known to take anglers’ bait in the form of mice, birds, and even small rabbits, despite it’s “teeth” being on a bony, circular structure located deep in its throat. 

A photo of a humpback chub

Humpback chub (Gila cypha)
The humpback chub has a pronounced muscular hump behind its head, giving this fish a striking, unusual appearance. Unlike the other three species, humpback chub stay in deep canyon habitat for their entire lives. The hump that gives this fish its name acts as a stabilizer that helps it maintain position in whitewater conditions. The humpback chub uses its large fins to “glide” through slow-moving areas, feeding on insects that become trapped in water pockets.

Humpback chub has an olive-colored back, silver sides, a white belly, small eyes and a long snout that overhangs its jaw. Like the Colorado pikeminnow and bonytail, the humpback chub is a member of the minnow family. The humpback chub is a relatively small fish by most standards –only growing to
about 20 inches and 2.5 pounds. Humpback chub can survive more than 30 years and typically spawn as young as 2 to 3 years of age during the March through July spawning season.

A fish biologist holds a razorback sucker showing of its keel

Razorback sucker (Xyrauchen texanus)
Three to 5 million years ago, a unique-looking fish with a sharp-edged keel “razorback” behind its head swam the Colorado River and its tributaries. The razorback sucker is most closely related to “lake suckers” and is the only member of the genus Xyrauchen. One of the largest suckers in North America,
the razorback sucker can grow to 3 feet in length and can live for more than 40 years. Razorback sucker eat insects, plankton, and plant matter on the bottom of the river using their soft sucker mouth.

Spawning occurs at age 2-3 during high spring flows when razorback sucker migrate to cobble bars to lay their eggs. Larvae drift from the spawning areas and enter backwaters or floodplain wetlands that provide a nursery environment with quiet, warm, and shallow water. These protected environments allow young razorback sucker to grow beyond fingerling size, dramatically increasing their chance for survival. As they mature, razorback sucker leave the wetlands in search of deep eddies and backwaters where they remain relatively sedentary, staying mostly in quiet water near the shore. In the spring, razorback sucker commonly swim long distances to return to where they were spawned.

Rare Native Fish are a Living Example of the History and Heritage of the Upper Colorado River Basin

For generations, these unique native fish have played an important role throughout the region. They were a valuable food resource for many early settlers moving west, as well as a plethora of terrestrial animals living alongside the river.  They are an important part of the heritage of the desert southwest. Above are photos of large Colorado pikeminnow captured in the early 1900’s on the Colorado and Green Rivers.