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 plans to announce Thursday that it will recommend reclassifying the ancient and odd-looking razorback sucker from endangered to threatened, meaning it is still at risk of extinction, but 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. By the 1980s they had dwindled to about 100. Researchers blame non-native predator fish that attacked and ate the razorbacks and dams that disrupted their habitat.
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.
Wildlife officials began reining in non-native predator fish with nets and screens to keep them from escaping reservoirs, or removing them by electrofishing — stunning them with electricity and euthanizing them with an overdose of anesthetic.
The Fish and Wildlife Service began working with dam operators to time water releases to help razorbacks spawn and restore flood plains for them to mature. Some dams were modified to help razorbacks to get by.
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.
The razorback sucker’s name comes from a sharp-edge, keel-like ridge along its back behind its head.