Endangered Razorback Sucker Returns to Grand Canyon Waters

Background

The Razorback Sucker, Xyrauchen texanus, was once one of the most common big river fish endemic to the Colorado River Basin.  Characterized by a muscular predorsal keel, small eyes embedded in a depressed head, and thick, leathery skin, the razorback has a prehistoric appearance that is highly adapted to the extreme stresses of irregular flow and high sediment load in the historically free-flowing Colorado river.  A combination of dam construction resulting in habitat loss as well as predation from invasive species have led to a significant decline in Razorback populations and the sucker’s subsequent listing as endangered in 1991.  Until its recent discovery in the Grand Canyon, the razorback had long been considered extirpated from large portions of the mainstem river, leading wildlife officials to speculate on the significance of their recent discovery.

Significance of the Razorback’s Return

Researchers had good reason to be surprised by the lone Razorback’s appearance during a recent electric sampling of fish stock in the Grand Canyon section of the Colorado River.  The sucker, which researchers had not seen in the canyon for more than twenty years, is the subject of extensive State and Federal conservation and recovery efforts.  When the federal government listed the Razorback as an endangered species in 1991, they also designated critical habitat in the Colorado Basin and implemented a federal recovery program.  Biologists suspect that the individual discovered in the Grand Canyon may have migrated nearly fifty miles upstream from Lake Mead, where mandated recovery efforts protected a self-sustaining population of 250-500 adult razorbacks for the past twelve years.  Similar recovery efforts, notably in Lake Mohave, have been hampered by high predation rates from non-native species such as striped bass, sunfish, and channel catfish.  While the discovery of a razorback so far from the nearest known self-sustaining population raises the question of whether Razorback suckers might someday re-populate the Grand Canyon, the impacts of the Glen Canyon Dam on Razorback habitat in the Canyon represent a major hurdle to the species’ return.

Completion of the Glen Canyon Dam in 1963 transformed the Colorado River as it runs through the Grand Canyon.  Where flows once peaked with the late spring runoff, demands for hydroelectric production now dictate flow rates that peak in late summer and winter months.  Water that historically varied from 35-85 degrees Fahrenheit between summer and winter months now emerges from the depths of Lake Powell (the reservoir behind Glen Canyon Dam) and enters the Canyon at a near constant 48 degrees.  Heavy sediment loads that once scoured channels and reinforced sandbars throughout the Canyon are now deposited behind the dam. Such drastic changes in river conditions following dam construction have played a major roll in the decline of native Colorado River Basin fish species.  Along with the Razorback Sucker, three other species (Bonytail, Colorado Pikeminnow, and Humpback Chub) endemic to the Colorado River Basin are listed as endangered.

Conclusion

The appearance of a Razorback Sucker in the Grand Canyon has raised the question of whether endemic species extirpated by Glen Canyon dam may someday re-establish populations in their native habitat.  While the implications of the Razorback’s return remain unclear, the discovery serves as a potent symbol of the complex history of the west’s most litigated river.


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