DENVER – Another rare Colorado River fish has been pulled back from the brink of extinction, the second comeback this year for a species unique to the Southwestern U.S.
The U.S. Fish and Wildlife Service is recommending reclassifying the ancient and odd-looking razorback sucker from endangered to threatened, meaning the danger is no longer immediate.
Hundreds of thousands of razorbacks once thrived in the Colorado River and its tributaries, which flow across seven states and Mexico. They include the San Juan River through northwestern New Mexico.
By the 1980s, razorback sucker numbers had dwindled to about 100. Researchers blame non-native predator fish that attacked and ate the razorbacks, and dams that disrupted their habitat.
Their numbers have bounced back to between 54,000 and 59,000 today, thanks to a multimillion-dollar effort that enlisted the help of hatcheries, dam operators, landowners, Native American tribes, and state and federal agencies.
“It’s a work in progress,” said Tom Chart, director of the Upper Colorado River Endangered Fish Recovery Program. “We get more fish out in the system, they’re showing up in more places, they’re spawning in more locations.”
The razorback sucker’s name comes from a sharp-edge, keel-like ridge along its back behind its head. Chart thinks the ridge may have evolved to help the fish stay stable in the turbulent waters of the Colorado. It can grow up to 3 feet long and live up to 40 years.
Razorbacks have been around for between 3 million and 5 million years, but trouble arrived as the population expanded in the Southwest. State and federal agencies began introducing game fish into the Colorado without realizing they would devour the native fish, Chart said. A spurt of dam-building was a boon to cities and farms, but interrupted the natural springtime surge of melting snow, which in turn shrank the floodplains that provided a safe nursery for young razorbacks.
Dams also made parts of the rivers too cold for razorbacks, because they release water from the chilly depths of reservoirs. And they blocked the natural migration of the fish.
By the late 1980s, most of the wild razorbacks were old, an ominous sign they were no longer reproducing, Chart said. The Fish and Wildlife Service began capturing the remaining wild razorbacks and moving them to hatcheries to begin rebuilding the population.
The agency designated razorbacks an endangered species in 1991. Biologists began restocking rivers with hatchery-raised razorbacks in 1995. Now, about 55,000 are released into the Colorado and its tributaries annually.