The latest stage of the rescue operation began on a crisp morning last October, hours before sunrise. In the predawn darkness, a small army of biologists piled into pickup trucks and drove deep into central Arizona’s canyon country, halting finally at the lip of a rose-hued chasm deep enough to swallow the Empire State Building twice over. The crew clambered into a Bell 407 helicopter, which promptly rolled off the gorge’s lip, skimmed along its striated walls, and deposited the team, along with 10 days’ worth of gear and food, in a scrubby patch of mesquite alongside the Little Colorado River. The six-person group—scientists, seasoned volunteers, and one out-of-place journalist—was now alone in the desert, with little more than a week to complete its mission: to find, capture, and relocate 300 of the strangest-looking fish in the Southwest.
The Little Colorado River, or LCR, is one of the last strongholds of the humpback chub, a creature whose numbers have been decimated over the past half century by dams in the Colorado River Basin. The foot-long fish sports a Quasimodo-ish bulge that rises from its back like the prow of flesh between a bison’s shoulders. Though the protuberance resembles a body-length tumor, it’s actually an exquisite adaptation, a stabilizer that helped the fish navigate the roiling waters that once tore through the Colorado River Valley. Steadied by its hump, Gila cypha has traveled this watershed for up to five million years, roughly as long as the Grand Canyon has existed. One 19th-century prospector reported schools of chub “so thick that you can lean over the water’s edge and pull them out by the tail two at a time.”
Today, however, a paltry 10,000 adult chub persist in the canyon. Around three quarters of the survivors hang on in the Little Colorado, an undammed 340-mile tributary of the Colorado. For two decades, government scientists have monitored and nurtured this population in hopes that it will disperse throughout the watershed. “The LCR is the best of what’s left,” said Mike Pillow, a sandy-haired U.S. Fish and Wildlife Service biologist, as he sorted coolers of steaks and beers in the shallow cave that the team uses each year as a makeshift camp.
Though Pillow and his colleagues net and track chub several times a year, this trip had an additional purpose: relocating 300 baby chub upstream to prime habitat above a waterfall. Upstream of the falls, insect prey is abundant, while invasive predators like trout are scarce. Years of such translocations have incrementally expanded the species’s range, buffering it against extinction. “We want them to imprint on the water up there when they’re in these smaller life stages,” Pillow said. “If they get flushed out, they should go right back up.” (The stepwise falls aren’t too steep for the fish to climb.)
No sooner had the biologists landed, however, than they realized their task would be much harder than anticipated. Torrential rains had swollen the Little Colorado and churned the usually turquoise waters into chocolate milk. Pillow feared the fish would hunker down and be less likely to swim into the scientists’ nets. Sure enough, the first three days of the expedition were a bust: Each morning the crew waded into the sludgy flow, wrestled their cylindrical nets to the surface, and brought up only mud. At night they gloomily tossed sticks into the campfire.
Where, they wondered, were the chub?
* * *
The humpback chub’s decline began in 1963, when the newly completed Glen Canyon Dam began impounding the Colorado River. The 710-foot-high wall was controversial from the get-go. To proponents it represented a technological triumph that would supply power and water to western states. Detractors mourned the inundation of Glen Canyon, a sublime chasm submerged beneath the new reservoir of Lake Powell. “All dams are ugly,” claimed Edward Abbey, whose 1975 novel, The Monkey Wrench Gang, revolves around eco-terrorists striving to blow up the despised concrete edifice. “But the Glen Canyon Dam is sinful ugly.”
The structure also had grim consequences for the Colorado River’s native fish. Historically, some 60 million tons of sediment washed through the Colorado Basin each year, building sandbars and backwaters as it settled—ideal sheltering grounds for young fish. As Glen Canyon Dam prevented sediment from drifting downriver, that prime habitat soon degraded. Moreover, humpback chub require warm water—at least 61 degrees Fahrenheit—to spawn and grow. The dam, however, releases its pulses from Lake Powell’s frigid depths, where temperatures hover around 46 degrees. Under those conditions, the fish grow slowly—and smaller chub are easier prey for invasive predators. Deprived of habitat and warm water, humpback chub were listed as endangered in 1967. Two of their cousins, bonytail and roundtail chub, vanished from the lower river altogether.
Though humpback chub remain rare, it’s not for lack of experimentation. In 1996, 2004, and 2008, the U.S. Bureau of Reclamation tried to replicate historical floods, releasing huge surges of water from the Glen Canyon Dam. The ersatz floods temporarily rebuilt some of the Colorado’s sandbars, yet the chub didn’t rebound. In fact, the 2008 event may have made things harder for chub: In the aftermath, exotic rainbow trout exploded, perhaps crowding out native fish. Since then, managers have tweaked the timing and volume of the man-made floods. Unleashing high flows in the fall, rather than the spring, has prevented further trout booms. And in 2012, the U.S. Department of the Interior announced that the dam would release high flows more frequently, a decision then-secretary Ken Salazar called “a milestone in the history of the Colorado River.”
Still, if the river isn’t warm enough to stimulate spawning and growth, the floods won’t provide much help. That’s where climate change might actually give humpback chub a boost. Years of drought have lowered Lake Powell’s surface and heated its depths, and the temperature of water passing through the dam has climbed two degrees in two decades. (Of course, warmer waters are projected to spell disaster for native fish just about everywhere else.)
But humpback chub aren’t the only fish that might thrive as conditions change—predators could benefit, too. Last summer surveyors found thousands of green sunfish, an eastern native stocked by anglers in the early 1900s, thriving below Glen Canyon Dam, where they’d never before been reported in significant numbers. In light of the discovery, the river’s managers elected to skip a planned flood for fear it would wash the invaders downriver.
Put it together, and there’s no easy path forward on the Colorado River: When the river runs cold, the fish don’t spawn; as it warms, new enemies gain a fin-hold. “The more we learn, the more complicated we realize it is,” said Ted Melis, deputy director of the U.S. Geological Survey’s Southwest Biological Science Center. “If you’re a resource manager, you’re left scratching your head.”
Conditions in the Little Colorado, by contrast, are far friendlier. In the searing desert summer, water temperatures in the undammed tributary can exceed 75 degrees: hot enough to deter trout, and just right for humpback chub. Any comeback for the odd-looking fish, therefore, likely has to begin in the muddy depths of the Little Colorado—which is why Mike Pillow and his team were so desperate to find their fish.
* * *
After three chub-free days, Pillow’s crew changed tactics. Instead of setting nets and waiting for chub to come to them, the scientists would go to the chub. The team pulled out seine nets—mesh curtains bookended by wooden poles, like giant scrolls — and dragged them over the muddy bottom, scooping up fish as they trudged along. Shoes were sucked into the mud. Knees collided with boulders. Even the vegetation seemed determined to hinder the chub chasers: Phragmites reeds sliced skin, prickly pear jabbed feet, tamarisk branches whacked faces.
The crew, now finally catching their quarry, hardly minded the hardships. The chub army awoke to the trills of canyon wrens, ate dinner beneath swarms of pinwheeling bats, slept under a moon luminous enough to read by. “Let’s just hit that spot over there,” Pillow said, time and again, his soaked khaki shirt clinging to his skin, as he nodded toward a promising pool. “They’ve got to be holed up somewhere.”
Slowly the makeshift aquarium—a garbage can standing upright in the river, perforated with small holes to allow circulation—filled with baby chub, silvery, finger-length fry that hadn’t yet developed their trademark humps. On the fifth afternoon of hauling the seines through the river, the biologists netted their 300th captive. The team exchanged a few tired handshakes, relieved to have completed their mission.
Moments later, however, nature once again threatened to sabotage their efforts. The sliver of sky visible through the canyon’s frame darkened with rain clouds, and the crew raced for shelter in a shallow cave. No sooner had they ducked inside than the storm exploded, hurling lightning at rock ramparts overhead and flinging thousand-foot waterfalls off cliffs. Boulders rolled from their perches and detonated in the sand. The scientists squatted in their refuge, agonizing over the 300 chub sloshing in the floating tank.
The fish survived (as did the biologists), and two days later the helicopter returned to transport the chub upriver. As the chopper whumped into the canyon, crew member Jim Walters, a Fish and Wildlife Service technician, assumed his role as translocation commander-in-chief.
“Fill this bucket!”
“Tie down that rope.”
“Buckle this strap!”
Under his capable instruction, the crew transferred the chub into the 55-gallon steel drum. Soon the chopper would airlift the drum and its precious cargo above the waterfall. Though the jury-rigged setup was a far cry from the engineering feat of the Glen Canyon Dam, both served as testaments to human ingenuity—and to the contradictions inherent in our interactions with the natural world. We destroy and we preserve, often in the same watershed.
“Go, go, go!” Walters called as the helicopter wobbled nearer, flattening the mesquite with its rotor wash. He hooked the dangling tow rope to the drum and flashed the pilot a thumbs-up. The aircraft rose, several hundred pounds of steel and water and fish and hope suspended beneath its belly, and 300 humpback chub disappeared into the sun rising up the canyon, bound for their new home.
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