Four "Big-River" Endangered Fishes

This post will explore a series of endangered species that reside along the Colorado River. I will investigate four fish species in particular, the Colorado pikeminnow, razorback sucker, humpback chub, and the bonytail chub, all of which are federally endangered.

Due to both the climatology of the Southwest and the increasing demands for Colorado River water for human purposes, many species have suffered the consequences.  Historically, the Colorado River Basin was home to 30 species found no where else.  Today, four of these 30 species are extinct and 16 are listed as threatened or endangered under the Endangered Species Act.

Photo courtesy of lh4.googleusercontent.com

A Brief Synopsis of the Endangered Species Act

According to the Endangered Species Act (ESA), a species listed as “endangered” means a species is in danger of extinction throughout all or a significant portion of its range. “Threatened” means a species is likely to become endangered within the foreseeable future. Once a species is listed, both the species and their habitat is protected by prohibiting the “taking” of listed species. “Taking” is defined by the ESA as “to harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect or attempt to engage in any such conduct.” Prohibited actions may also include “significant habitat modification of degradation where it actually kills or injures wildlife by significantly impairing essential behavioral patterns, including breeding, feeding, or sheltering.”

Four “Big-River” Fishes

Photo courtesy of www.mountainijournals.com

Four fish species along the Colorado River who are currently listed as endangered by the ESA are the Colorado pikeminnow, razorback sucker, humpback chub, and the bonytail chub.  These four fishes are unique in that they are only found in the Colorado River Basin.  All four are large, long-lived, warm-water species that are thought to have evolved three to five million years ago.

Colorado Pikeminnow
Photo courtesy of http://www.natgeocreative.com

Colorado Pikeminnow

The Colorado pikeminnow is noted for being the largest species in the minnow family in North America. Records show individuals of this species growing to a length of 6 feet long and weighing over 100 pounds.  Today, the Colorado pike minnow generally grows to a length of two and a half feet weighing between 5 and ten pounds.

Razorback Sucker

Razorback sucker
Photo courtesy of dnr.state.co.us

The razorback sucker is another big fish characterized by its sharp, bony, “razorback” hump. This species can grow up to lengths of three and a half feet and weigh up to 15 pounds.  This species once thrived throughout most of the medium and large sized rivers of the Colorado River Basin, but its range has dwindled to only the Colorado River above the Grand Canyon, and various big lakes on the lower Colorado River.

Humpback Chub

Humpback Chub
Photo courtesy of mediad.publicbroadcasting.net

Humpback chub are distinguished by the abrupt, fleshy hump behind their head. This species can grow to lengths of three and a half feet and has a body that is almost entirely scaleless.  This fish thrives is deep, swift-water habitats and usually is found in smaller populations. Historically, the humpback chub ranged on the Colorado River from below present-day Hoover Dam upstream into Colorado, aswell as in portions of many of the Colorado River tributaries in Arizona, Utah, Colorado, and Wyoming.  Today, there are only seven population centers of the humpback chub.

The location of the humpback chub population centers in the Colorado River Basin.
Photo courtesy of www.utexas.edu

Bonytail Chub

Bonytail Chub
Photo courtesy of www.coloradoriverrecovery.org

The bonytail chub is the rarest of the four fish species discussed.  This species can grow to over two feet long.  Once found in a number of states, including Arizona, California, New Mexico, Utah, and Wyoming, this fish species has since experienced the most abrupt decline of any of the long-lived fishes native to the main-stems of the Colorado River system and, because no young individuals have been found in recent years, has been called functionally extinct.

Reason for the Decline in “Big-River” Fishes

Hoover Dam
Photo courtesy of 4.bp.blogspot.com

The reasons for becoming listed vary for each of the four species but collectively, the construction and management of dams and diversions has effected these populations the most.  The combination of regulated flows, decrease in sedimentation and change in pH levels downstream due to dams has degraded the ecosystems and habitats of the “big-river” fishes.  For the humpback chub, a threat to its species has been competitive non-native predators as well as the spread of parasites and diseases.  Lastly, with the increase in demand for Colorado River water, a conflict between consumers and the ESA arose over the appropriate use of water.

Recovery Programs and Their Effectiveness

Currently, there are two main recovery programs that the U.S. Fish and Wildlife Service is working on along side with other state and federal agencies, water and power organizations, and tribes in order to recover the four “big-river” fish species. The first program is the Upper Colorado River Endangered Fish Recovery Program established in 1988, which includes the Colorado River upstream of Glen Canyon dam.  The second project is the San Juan River Basin Recovery Implementation Program created in 1992, which includes the entire San Juan River, a significant tributary of the Colorado River.

Photo courtesy of image.slidesharecdn.com

There are a number of key elements within these two programs to aid in recovering the four fish species. Below are a few of the main areas of emphasis.

• Improving river flows and habitats through modification of dam operations and cooperative agreements to enhance flows
• Construction of five fish passages around dams and diversions to link more then 375 river miles of designated critical habitat
• Instillation of fish screens to prevent fish from getting caught in irrigation canals
• Restoration of 3,000 acres of floodplain habitat
• Raising endangered fish in hatcheries and stocking them to reestablish naturally self-sustaining populations

It is important to note that these projects would not be possible without the cooperation of multiple parties working to recover endangered fish while water development proceeds in accordance with federal and state laws and interstate compacts. Today, with its demonstrated success, the Upper Colorado River Endangered Fish Recovery Program has become a model to protect other endangered species.  Its biggest success thus far has been in creating stable populations for the Colorado pikeminnow who is on track to be delisted within the next few years.

In my next post, I will discover the complexities surrounding the Colorado River Delta, its ecological importance, issues that impact it and what is being done internationally to preserve and enhance its existence.