What do you see when you close your eyes and picture the Grand Canyon? Your answer, most likely, is rock—limestone walls glowing rose at sunset, sandstone layered like parchment, ancient schist gleaming black along the banks of the Colorado River. Geology is the canyon’s main event, the attraction that in 2016 lured more than 6 million visitors. Ecology, for most, is an afterthought.
That’s a shame, because the Grand Canyon contains one of North America’s quirkiest ecosystems—and the best action is underwater, in the latte-colored churn of the Colorado. Although the Colorado River possesses North America’s lowest native fish diversity, it has the highest ratio of endemic species, fishes that are found nowhere else on Earth. In this warm, turbulent, geographically isolated watershed, ecological niches that might be filled by trout in other rivers are instead occupied by tough-as-nails minnows and suckers. The Grand Canyon was long ruled by evolutionary oddities like the humpback chub (Gila cypha), a silvery omnivore endowed with a distinguished ridge just behind its head, and the Colorado pikeminnow (Ptychocheilus lucius), the predatory king of the Cyprinidae, the minnow family, which can grow as long as a human. Early anglers caught the mammoth carnivore—yes, really, a six-foot-long minnow—on hooks baited with small rabbits.
Glen Canyon Dam, a concrete wall twice as tall as the Statue of Liberty, changed the canyon’s ecosystem forever. To the Bureau of Reclamation, the federal agency that completed the titanic barrier in 1963, the dam was a technological triumph: It yoked the capricious Colorado, transformed inhospitable desert into fertile farmland, and powered the Southwest’s metastasizing cities. To the canyon’s aquatic inhabitants, it was an existential crisis. The dam blocked spawning grounds, stifled the deposition of habitat-building sediment, and created prime conditions for non-native rainbow trout that had been stocked for anglers. The pikeminnow, the roundtail chub, and the bonytail soon vanished from Grand Canyon National Park. The reign of the canyon’s native fishes had seemingly come to an end.
Lately, however, one species has launched a comeback. The razorback sucker (Xyrauchen texanus), a homely bottom-dweller listed as endangered since 1991, has resumed spawning in the canyon after a decades-long absence. Razorbacks are stout fish, sized and shaped like a block of firewood, with creamy yellow bellies and flanks the greenish-bronze of a dull penny. A bony prow, like the keel of a ship, rises from its back, earning it the nickname “buffalo fish.” (Scientists think the hump may help to keep the fish stable in raging floodwaters.) What razorbacks lack in loveliness, they make up in longevity: They can live more than 40 years. There may be suckers swimming in the Colorado River that are as old as the Endangered Species Act itself.
The sucker’s renaissance has delighted and confounded scientists. “The fact that they’re hanging on in places that we never expected to find them is really encouraging,” says Scott Durst, a U.S. Fish and Wildlife Service biologist. “It shows that recovery is an attainable goal. These are tough, resilient fish.” And the sucker’s success isn’t just a feel-good story. If biologists can figure out why razorbacks are bouncing back, and how to aid their return, they might be able to guide the Colorado River’s management to benefit all its species. But can Glen Canyon Dam, the Southwest’s most controversial piece of infrastructure, ever coexist with a healthy assemblage of native fishes?
To find out, I hiked down to the sandy floor of the Grand Canyon one diabolically hot morning this past June. A mile below the rim, I rendezvoused with a blue rubber raft as long as a minke whale, stocked with mesh seine nets, sonar-detecting headsets, and bottles of chemical preservatives. A spiderweb of straps cinched a heap of dry-bags tight to the frame, rigging that would soon be tested by monstrous rapids. I clambered aboard and settled atop a metal crate, inadvertently sitting on eight days’ worth of granola bars and beef jerky. “You may not wanna cover that snack box,” the pilot, Carolyn Alvord, called as she motored us into the current. “That wouldn’t be a popular move.”
The precious snacks would fortify Alvord and five fish biologists as they scoured more than 200 miles of rapids, eddies, and backwaters in search of larval razorback suckers. Adult razorbacks are returning to the canyon to spawn, yes—but where, when, and how successfully remains something of a mystery, one that the crew hoped to crack. Yet finding scarce razorback larvae—translucent newborns no larger than a sliver of fingernail—in the mighty Colorado seemed a hopelessly quixotic mission. It was like searching for needles in a haystack, if the needles moved constantly and the haystack was a surging, muddy, muscular river often interrupted by deadly whitewater.
The crew seemed undaunted. “You’ve gotta be an optimist to be a native fish biologist. These animals have a lot of cards stacked against them,” boomed Brandon Albrecht, a biologist with the burly physique and bonhomie of a high school football coach. “I always root for an underdog.”
As I soon learned, the challenge of catching larval razorbacks is less technical than ontological. You have no idea whether you are, in fact, catching larval razorbacks.
Within five minutes of embarking, Alvord grounded the raft on a narrow beach, and the week’s fieldwork began. Adam Barkalow and Eliza Gilbert, biologists with American Southwest Ichthyological Researchers (ASIR), took me under their wing. (Although the research trip was led by the federal government, four of the five scientists were contracted from ASIR or BIO-WEST, Albrecht’s consulting firm.) The duo unfurled a seine net—a curtain of fine mesh suspended between wooden handles, like a giant scroll. Slogging chest-deep through the frigid Colorado, they gathered a school of squirming, transparent larval fish into their net. With a few adept swipes, Barkalow flicked the larvae into a clear plastic bag, as though they were county-fair goldfish. I squinted at the freshly hatched creatures, which lacked tails, fins, or discernible internal organs. They were merely, as Barkalow put it, “squiggles with eyes.”
Back at the raft, Gilbert squirted a few drops of formalin into the bag to preserve the fish for later identification, then stowed the catch in a steel case. When the fish are this tiny, she said, the only way to discern razorbacks from more common bluehead and flannelmouth suckers is through a microscope, using subtle diagnostics like the density of back speckles and muscle fibers. If these squiggles with eyes were razorbacks, it would give the team valuable clues about where and when the fish were spawning, and the conditions favored by their larvae. But we wouldn’t know whether we’d caught even a single razorback until months after we’d departed the canyon. I tried to suppress my sense of anticlimax.
A decade ago, capturing any razorback larvae in the Grand Canyon would likely have been impossible. A century of Southwestern dam-building—15 large dams on the mainstem Colorado, and dozens more on its tributaries—had left razorbacks diminished and scattered, forcing scientists to supplement most remaining populations with fish grown in hatcheries. Today, the largest wild population dwells in Lake Mead, the branching reservoir, formed by Hoover Dam, that laps at the Grand Canyon’s terminus. Although the lake is chockablock with striped bass and other hungry invaders, it supports as many as 500 spawning adult razorbacks. Yet no survey had detected them moving into the canyon itself since the early 1990s, and biologists considered them locally extinct.
In 2010, though, scientists began hearing pings from radio-tagged suckers at the Colorado’s junction with Lake Mead, suggesting the fish might be traveling upriver into the Grand. Two years later, biologists with the Arizona Game & Fish Department caught a wild razorback in the canyon, fifty miles above the reservoir. Surveys in 2014 and 2015 netted a handful of larvae, proving that razorbacks weren’t just vacationing within Grand Canyon National Park, but spawning there. At a time when most of the Colorado’s native fish were hanging on for dear life, razorbacks were somehow expanding their range.
But the razorback’s return may be part mirage. Scientists have captured both adults and larvae in the canyon, but they haven’t yet turned up any juveniles or sub-adults. Decades-old fish appear to be moving up from Lake Mead to spawn, yet their offspring are struggling to survive. Our mission, then, was two-fold—in addition to seining larvae, we also hoped to net ourselves a juvenile. “Those one-year-olds are the Holy Grail for this species,” Gilbert told me.
Every grail needs its crusader, and the Indiana Jones on our expedition was Brian Healy, lead fish biologist for Grand Canyon National Park. Healy, a grizzled Wisconsin native who wears his gray hair pulled back in a ponytail, is something of a renaissance man: At home, he arises at 5 am to play Pearl Jam and Red Hot Chili Peppers riffs on his electric guitar to relax before the daily grind. As we drifted downriver, he rattled off Grand Canyon trivia: There was Havasu Creek, where the Park Service has translocated hundreds of humpback chub; there was an outcropping of Vishnu schist, some of the world’s oldest exposed rock; there was the cave where foolhardy entrepreneurs had set up an ill-fated bat guano mine. He often rhapsodized about the canyon’s bizarre native fish, defending them against the complaints of anglers who’d prefer to see the place given over to rainbow trout.
“You always get that one guy who says, ‘Well, can you eat ‘em? No? Then what good are they?’” Healy groused as he tore open a packet of jerky. “Well, they’re part of the canyon, like the river and the rocks.”
Healy has a theory about why razorback larvae aren’t reaching adulthood, one that he shares with many biologists. The Glen Canyon Dam made the Colorado River simultaneously more stable, by eliminating massive spring floods, and more volatile, by instituting tides. Yes, tides. In the morning, as millions of people in Phoenix and other cities flick on their lights and air conditioners, dam managers crank up flows through Glen Canyon’s turbines to meet power demand. At night, while the Southwest slumbers, they dial the river back. While we were in the canyon, the river’s flow ranged from 10,000 to 17,000 cubic feet per second. The fluctuations, called hydropeaking, cause the river to rise and fall by several feet each day. Incautious rafters will sometimes awake to find their vessels stranded in the sand at high tideline.
No one’s certain what these artificial tides have meant for fish, but it’s likely nothing good. In 2012, Ted Kennedy, a research ecologist at the U.S. Geological Survey, recruited raft guides to serve as citizen scientists, paying them $15 per sample to deploy insect-attracting fluorescent light traps each evening when they made camp. When Kennedy analyzed the guides’ catches, he found that the canyon was almost completely bereft of mayflies, stoneflies, and caddisflies, river-edge specialists whose eggs are most likely to be exposed and desiccated by hydropeaking. Tiny blackflies, which lay eggs in open water, are relatively unfazed by tides, but, Kennedy told me, they don’t compensate fish for the loss of more nourishing prey. Scarce food, more than perhaps any other factor, is holding native fishes back.
During our second day on the river, we pulled over to run our seines along a cobble bar. Nothing. Healy knelt to inspect the lifeless rocks. “In every other river, that cobble would be covered with caddis and mayflies and all kinds of algae,” he said glumly. “Here you don’t see anything because these huge tidal fluctuations leave it dry half the time.”
Even in the pre-dam era, Healy added, the Grand Canyon’s tight confines would have challenged larval razorbacks, which prefer to grow up in wide, shallow floodplains. What little habitat the canyon had once afforded, hydropeaking now erodes and dries out. “Razorbacks need warm, stable habitats full of food to get out of that larval stage,” Healy said. “They’re not getting that here.”
The Colorado River, as befitting a watercourse that runs through a desert, was historically a warm river. Sometimes its flows climbed to a bathtub-like 84 degrees. After the Glen Canyon Dam’s construction, the once sunlit river emerged instead from the dark, frigid depths of Lake Powell, the reservoir that formed behind the wall. The Colorado’s temperature fell to around 46 degrees—roughly as cold as the Atlantic Ocean off the coast of Maine in December. The icy waters devastated native fish, particularly the humpback chub, whose juveniles require warm temperatures to grow large enough to escape predators.
In the last decade, however, Lake Powell has drained to less than half its capacity, as declining snowpack has lagged behind thirsty agriculture. As Powell has shrunk, the river has climbed to around 50 degrees—still chilly, but balmy enough in places to encourage the growth of native fish. Sure enough, our seine hauls netted the most juveniles in hot, stagnant backwaters where the temperature hovered around 80 degrees. These are some of the only fish in North America that stand to profit from drought.
The river’s rising temperature is, in fact, a double-edged sword. “Did you notice that there aren’t any invasives in these samples?” Albrecht said after one especially productive seine pull. “Where else in the country are you gonna see a river like that?” As the canyon warms, however, scientists fear that it could become more hospitable to hungry, warmth-tolerant intruders like smallmouth bass and sunfish. Cold flows have stunted native fishes’ growth, but they’ve also served as a bouncer, preventing undesirables from crashing the party.
The Colorado’s native fish have also gotten some help from Glen Canyon Dam’s managers. In 1996, the Bureau of Reclamation unleashed the first in a series of “high flow experiments”: artificial, sediment-bearing floods designed to replenish the sandbars and side-channels that native fish rely on to spawn and shelter. The experiments have a mixed record—a faux flood in 2008 accidentally triggered an explosion of trout—but as the feds have refined the timing and volume of the pulses, they’ve succeeded in temporarily rebuilding sandbars, a boon for fish and rafters alike. In 2012, the government declared that it would release high flows whenever conditions were favorable, an announcement that dismayed power providers and cheered conservationists. The most recent ersatz flood tore through the Grand in November 2016, when managers unchained 36,000 cubic feet per second for four straight days.
All this meddling is intended to help one fish in particular: the humpback chub, listed as endangered since 1967. “The chub is the queen of the canyon—it drives management, and it’s one of the most studied fish in the world,” Mark McKinstry, a Reclamation biologist, told me. The razorback, meanwhile, has been mostly ignored, for the simple reason that no one even realized it still dwelled in the canyon. The government’s newest plan for managing the dam’s flows, published this past October, references the humpback chub 36 times. Razorbacks only merit four mentions. “We still don’t know how best to manage for their recruitment,” McKinstry acknowledged.
One change that would surely help razorbacks, and all the canyon’s native fish, is ending the daily tides that wipe out aquatic insects and destabilize the Colorado’s food base. But replacing hydropeaking with steady flows is anathema to power distributors, which lean on the dam’s 4.5 billion kilowatt-hours annually—the equivalent of 2.5 million tons of coal, or 11 million barrels of oil—to keep the lights on in seven states. The government’s plan, which will dictate Glen Canyon’s management for the next 20 years, proposes something of a compromise: low, steady flows on summer weekends, when power demand hits its nadir.
“You give these insects favorable egg-laying conditions two days a week, and that might be enough to overcome the bottleneck while still allowing for hydropower production,” said the USGS’s Ted Kennedy. “That’s what’s exciting, that we can maybe have our cake and eat it too.”
But environmentalists aren’t yet reaching for their forks. George Washington Hayduke, the swashbuckling protagonist of Edward Abbey’s ecoterrorism paean The Monkeywrench Gang, once strove to blow the dam to smithereens. Although the opposition today is more genteel, it’s no less vehement. Lake Powell’s shrinkage has given new ammunition to the “Fill Mead First” plan, a proposal to open Glen Canyon’s gates and consolidate its impounded water with Lake Mead, 300 miles downriver. “Climate change, and the impacts that it will have on hydrology throughout the whole basin, requires us to think outside the box,” said David Wegner, a former Bureau of Reclamation fish biologist. The new plan, Wegner added, doesn’t go “nearly far enough.”
The paradox of the Grand Canyon is that it is one of the wildest landscapes in the country, and one of the most heavily managed. The Colorado wends hundreds of miles from urban centers, yet its every drop travels at the whim of an engineer in a control room. Reconciling ecological integrity with the demands of hungry, thirsty cities is a precarious balancing act, and the scales are still tipped toward civilization. In the Northwest, it is easy to argue for conserving salmon, a fish that sustains Native peoples and multi-million dollar commercial fisheries. In the Southwest, it is considerably harder to make the case for the humpback chub and razorback sucker, species that support no industry, provide no tangible ecosystem services, and are effectively invisible to the overwhelming majority of park visitors.
“Whenever I’m sitting on an airplane, someone will ask me what I do, and I’ll tell them I study endangered fish. They’ll say, ‘Um, why?’ I have yet to come up with an answer that would satisfy someone who doesn’t share my values,” Eliza Gilbert confessed one afternoon on the river. “You just have to care.”
The final day of our float carried us into the canyon’s most infernal reach, the uppermost tendril of Lake Mead. The river, once frisky and foaming, slowed into a wide, sluggish canal, and the canyon walls drew back to expose us to the merciless sun—the death orb, Healy called it. The thermometer read 118 degrees Fahrenheit; my skin cracked and peeled like baked mud in a dry arroyo. Even the rattlesnakes we encountered during our seining forays seemed too heat-struck to budge.
The further we drifted, the more parched the land became. The same drought that had diminished Powell had shrunk Lake Mead to just 37 percent of its volume. The lake’s surface had plummeted so far that the river had chewed through sediment that had been accumulating on Mead’s floor since 1935. In 2000, our raft would have floated atop the equivalent of a 12-story building; now it was as though we’d descended into the basement. Every few minutes a car-sized wedge of riverbank—nearly a century of built-up lake floor, now baking in the sun—sloughed into the river in a puff of dust.
The evaporation of Lake Mead has panicked human consumers, from Las Vegas casinos to Imperial Valley farmers. For the river’s biological community, however, it seemed a blessing. Reemergent side channels writhed with red-spotted toad tadpoles (Anaxyrus punctatus), and warblers and flycatchers flitted through new willows. “It’s pretty cool, how quickly the river regains its course,” Barkalow marveled.