GO! FISH.

By terry greene sterling photographs by tom bean

It's September. Slate-gray monsoon clouds hunch over Northern Arizona's Vermilion Cliffs, bruising the red bluffs with their shadows. In the valley below, a strange convoy roars down a narrow road that blades through sand and rock toward the Colorado River.

The four-vehicle convoy consists of a passenger car, a pickup towing a small Osprey motorboat, and two large stake-bed hauling trucks. One stake-bed carries a second Osprey motorboat in a metal cage. Both stake-beds haul long trailers. Latched onto each trailer is an inflated white-and-black rubber raft measuring more than 30 feet long. Each raft has a yawning belly lined with metal war-surplus ammo cans, set like crooked teeth.

The vehicles brake to a halt near historic Lees Ferry, where 19th and early 20th century settlers once ferried across the Colorado River. Clad in sandals and loose-fitting clothing, several men and women jump out of the convoy and expertly ease the two large rafts into the river. Ten people — four fisheries biologists, two volunteers and four technically savvy boat pilots — are assigned to this expedition, which is overseen by the U.S. Geological Survey (USGS) Grand Canyon Monitoring and Research Center in Flagstaff and the U.S. Fish and Wildlife Service. The expedition is tasked with documenting the effects of Glen Canyon Dam on the river knifing through the Grand Canyon by monitoring populations of the humpback chub, an endangered fish species as old as the Grand Canyon itself.

Humpback chubs are found only in the Colorado River Basin, and mostly in the Grand Canyon. For four days, photographer Tom Bean and I will join the expedition as it studies this species. We'll be dropped off downstream near Phantom Ranch, and hike out via the Bright Angel Trail.

Today, the Colorado River at Lees Ferry is the color of Chinese jade, slightly redolent of algae, and very cold. When early settlers ferried across here, the river was warmer, more temperamental and scented by the silt thickening its waters. What changed? The Glen Canyon Dam, about 15 miles upstream, was completed in 1963. The dam plugged the Colorado River, creating Lake Powell, a reservoir that now provides drinking water to 25 million people and banks water for droughts in compliance with multistate water pacts. Glen Canyon Dam churns out 5 billion kilowatt-hours of hydroelectric power each year as it hurls the Colorado River back into its downstream channel. Colder, clearer water released in unnatural sequences from the depths of thereservoir now feeds the river, altering downriver plant and animal habitats.

The science produced by this expedition will help inform the U.S. Department of the Interior as it comes up with a plan in the next two years on how best to manage water releases from the dam over the next two decades.

In deciding how to release water from the dam in the next 20 years, the department must consider how to account for the needs of dozens of Native American tribes, seven thirsty Colorado River Basin states, trout anglers, farmers, river-rafting companies and hydroelectric power users, as well as honor the Grand Canyon Protection Act, which protects the Grand Canyon and the threatened and endangered creatures that live there like the humpback chub.

The “Law of the River” dictates that water will be delivered from the dam. But Congress requires that the entirety of “resources” in the Grand Canyon — including the river and the creatures that rely on it — be protected, restored and improved by the way in which the water is released from the dam.

The Grand Canyon Trust, a conservation group that aims to protect and restore the Colorado Plateau, recently responded to an environmental impact statement that will help guide the department. The flows must be changed, the Trust writes, because under current dam releases, “cultural sites have lost much of their foundations; beaches have shrunk; many native plants and animals have been reduced in number; and 10,000 endangered humpback chubs compete for limited food with over 1 million trout.” Loss of sediment under “current dam operations” has “resulted in fewer and smaller beaches.” It has also “eliminated significant critical habitat for native fish. Sediment deposits create complex shorelines and underwater features that are used by native fish for spawning and rearing.”

The Trust wants the federal government to require two types of releases from the dam in the future: “regular high flows” to restore beaches and “seasonally adjusted steady flows” based on the natural rhythms of the pre-dam river, which would preserve beaches, protect native fish habitat and stabilize centuries-old cultural sites. Reconfiguring dam flows can be expensive, though, and hydroelectric power users prefer to keep costs low. In deciding how to regulate dam flows, the department will rely on a growing body of science, such as the findings soon to be produced by this raft expedition at Lees Ferry.

The crew checks on the rafts, now tethered to metal pounded into the buff-colored sandy beach. The crew lashes a long pontoon onto each side of each raft and inflates each pontoon with air. The two small Osprey motorboats bob in the river, tied to the rafts.

Carolyn Alvord, a former racehorse jockey from Connecticut and longtime Colorado River boat pilot, jumps on the kitchen raft. Short, sturdy and strong-minded, she checks the cargo of cast-iron pots, portable stoves, grills, soap, condiments, coffee, Turtles candy, knives, forks, spoons, cups, ice, 14 filled 5-gallon water jugs and enough food to sustain 12 people for nearly three weeks. Alvord will pilot the kitchen raft and command the kitchen.

cast-iron pots, portable stoves, grills, soap, condiments, coffee, Turtles candy, knives, forks, spoons, cups, ice, 14 filled 5-gallon water jugs and enough food to sustain 12 people for nearly three weeks. Alvord will pilot the kitchen raft and command the kitchen.

Shane Murphy is a 65-year-old mustachioed guidebook writer and biographer of Grand Canyon pioneer and storyteller John Hance. Murphy has piloted 128 trips down the river, explaining its wonders to tourists. After a stint guiding tourists in the Antarctic, he returned to Arizona, and the river. Now he's in charge of the large, awkward science raft, which can buck dangerously in rapids. Among other things, the science raft carries buckets, a giant winch for boat repairs, dozens of heavy nets (seine, trammel and hoop), notebooks, maps, a large bag of Aqua Mix fish-food pellets, half-inch-long “pit tags” containing microchips to be injected into fish for monitoring purposes, scanner wands to detect and read tags in fish that have already been injected, fish-measuring boards, a well-equipped first-aid kit, a plastic bladder of red wine, bright-yellow waterproof “dry bags,” camping equipment, folding chairs, a sun-and-rain shelter, extra Honda boat motors and two guitars.

food pellets, half-inch-long “pit tags” containing microchips to be injected into fish for monitoring purposes, scanner wands to detect and read tags in fish that have already been injected, fish-measuring boards, a well-equipped first-aid kit, a plastic bladder of red wine, bright-yellow waterproof “dry bags,” camping equipment, folding chairs, a sun-and-rain shelter, extra Honda boat motors and two guitars.

It's midmorning, and as we float downstream the sky is so clear I can see the moon overhead. The green river darkens in cliff shadows. Two big rafts follow the two noisy Ospreys, making good time in a 30-foot-deep river that travels into the Grand Canyon at about 4 miles per hour. The water is released from the dam today at about 8,000 cubic feet per second, a relatively slow flow that makes for a pleasant ride.

On the science raft, Randy Van Haverbeke takes in sights as familiar to him as breathing: the crimson cliffs; the seep willow, saltbush and snakeweed clinging to small sandy beaches; the lone blue heron fishing in shallows; the driftwood on cliffs high above the river, signaling a raging pre-dam flood. Van Haverbeke is 58 years old, a man of average height and build who wears aviator glasses and tucks his wavy gray-blond ponytail through the back slot of his ever-present baseball cap. He's a Copenhagen-dipping jokester who appreciates human company, but he's also a loner, and likes to let a big landscape swallow him. As a teenager, he began exploring the Grand Canyon, and he respects its power. As a committed fisheries biolo-gist, he's traveled the river or its tributaries more than 150 times, studying humpback chubs.

Geologists figure the Colorado River began creating the Grand Canyon between 5 and 6 million years ago. Fossils suggest hump-back chubs lived in the Colorado River Basin at least 5 million years ago, according to the 2008 book Late Cenozoic Drainage History of the Southwestern Great Basin and Lower Colorado River Region: Geo-logic and Biotic Perspectives.

This species could be as old as the canyon it evolved in. For millions of years, these silvery minnows, which can live to be 40 years old and can grow to be more than a foot long, survived floods and drought that ravaged the Colorado River Basin. Their namesake hump, which grows as the fish ages, remains a mystery. It might have evolved to help the fish balance and navigate in the fast water. Or it might have developed to prevent the fish from being swallowed by other giant minnows that once populated the Colorado River Basin.No one knows how many humpback chubs existed in the Colorado River Basin prior to the construction of Glen Canyon Dam, but scientists estimate that the species now occupies about 68 percent of its original habitat. Cold dam water and introduced predators like trout have decreased their numbers.

Today, scientists estimate there may be 10,000 to 11,000 adult humpback chubs in the entire Colorado River Basin. (About 2,000 to 3,000 live in the Upper Colorado Basin, upriver of Glen Canyon Dam. Another 7,650 or so live in the Colorado River and its tributaries downstream from the dam.) The Grand Canyon, according to USGS supervisory biologist Scott VanderKooi, is a "stronghold" for the species.

In 1989, scientists estimated that between 11,000 and 12,000 humpback chubs lived in the Grand Canyon; by the year 2000, their numbers had fallen to 5,000 to 6,000.Then, in 2009, the Grand Canyon populations made a modest comeback up to about 7,650 or so. That's still lower than the 1989 estimate, but scientists say the species continues to make modest gains in the Grand Canyon.

Van Haverbeke figures the population uptick was probably caused by several factors. Humpback chubs need to live in water of at least 61 degrees Fahrenheit or higher in order to spawn and grow normally. Dam-released Colorado River water usually registers 46 to 54 degrees Fahrenheit too cold for the fish to thrive.

But in 2000, a low release from the dam warmed the Colorado to about 56 degrees. In other years, the waters released from a shallower Lake Powell were warmed even more by drought. What's more, the humpback chubs' predators, like trout, declined throughout the river for unknown reasons between 2000 and 2007. And for three years, from 2003 to 2006, authorities removed close to 80 percent of the trout hoping to make a meal out of baby humpback chubs near a critical spawning area — the warm Little Colorado River, which spirals into the Colorado River in the Grand Canyon.

This expedition will monitor known populations of hump-back chubs, which explains why, in the late afternoon, we tie up at our first campsite — an uncomfortable rocky beach near loud rapids. Here, small pockets of the river are warmed by springs with bathtub-temperature water. The warm water attracts humpback chubs. One tiny population has spawned here.

Thirty hoop nets and eight trammel nets are loaded into the Ospreys. Hoop nets are meshed collapsible cylinders about the size of a garbage can. Attached to long cords tied onto boulders or branches, the submerged hoop nets contain bait that lure fish into their cavities. Once in, the fish seldom escape. The large trammel nets are more problematic. They traverse wide stretches of river and can stress fish trapped in their web. For fish safety, trammels must be checked three times this evening and removed at 11 p.m.

Boatmen Peter Weiss and Scott Perry, both technically trained in data collection, pilot the boats. Van Haverbeke; Robin Osterhoudt, an Arizona Game and Fish Department Colorado River researcher; and Mike Pillow, a fisheries biologist with the U.S. Fish and Wildlife Service, join Anya Fayfer, a Museum of Northern Arizona field and lab technician who has volunteered her time to the expedition on the Ospreys. This team will set the trammel nets, and throughout the night they will check for fish, measuring those caught in the trammel nets before releasing them into the black water. They catch three adult humpback chubs in the trammel net.

In the darkness, Osprey motors whine as they push through loud, roiling waters. In the morning, it's time to check and collect the hoop nets. By a warm spring seeping from fragrant, fern-laced umber-hued limestone, there's a very small humpback chub spawning area. This little population seems to be holding on.

After the nets and gear are stowed, we glide downriver, passing a bank of mauve-tinted limestone. We tie up at a large sandbar, about 80 yards long. The tan sand has the consistency of brown sugar, and a recent nameless visitor scrawled FREEDOM RUNNERS across a narrow part of the sandbar. Between the sandbar and the bank of gray boulders interspersed with sandy expanses of grass, Van Haverbeke and expedition co-leader Bill Persons, a fisheries biologist for the USGS, drag a seine net to see if they can find baby humpback chubs in the backwater.

Persons, 61, is a longtime fisheries biologist who has always loved rivers. He's a tall, even-tempered scientist with a tidy beard. On river trips, he wears a wide-brimmed straw hat that shades his shoulders. He wears it as he wades into the backwater carrying one end of the net and sinks to just above his shoulders, struggling for footing in deep muck. Brown silt billows up from the bottom, staining the green water. Persons balances himself, then drags the net with Van Haverbeke, who holds the other end and stands on the sandbar in his canary-yellow life jacket. They catch about 20 fish, mostly trout. No humpback chubs. They repeat the sequence, with Van Haverbeke in the muck this time. Pillow carefully helps pluck fish out of the net. Still no baby humpback chubs. The water is too cold.

"It's cold," I say when I gently lay my index finger on a humpback chub for the first time. We're about 2.5 miles upstream from the Little Colorado River spawning grounds now. In the two days we camp here, at the confluence of Awatubi Creek and the Colorado River, the crew nets, measures and documents the presence of more than 100 adult humpback chubs. The fish I touch is a big silver female, perhaps 25 years old, with graceful fins and a strong tail. Her small head extends quizzically from beneath her large hump. She has circular eyes that don't see very well, but well-developed senses of vibration and smell help her survive in silty waters. Her well-defined nares, or nostrils, sit on top of her dome-shaped snout. She has a large mouth. And no teeth.

She doesn't resist human handling when her eyes are covered with a cupped hand (Pillow's technique) or her belly is gently stroked (Van Haverbeke's technique). And when she slides back into the Colorado River, her silver body disappears in sun-silvered water.

"A really cool fish," Weiss later says of the entire species. "They developed in this place, they're part of it."

So is Weiss. At 58, he's spent most of his life as a boatman. First, he piloted tourist rafts. Now, he mans science-expedition boats. He's a quiet man who understands the river, and knows exactly where to find humpback chubs. "They like quiet places," he says. "Maybe we should all like quiet places."

exactly where to find humpback chubs. "They like quiet places," he says. "Maybe we should all like quiet places."

Thunder tumbles through the Little Colorado River canyon and into the Grand Canyon. The rain-swollen Little Colorado races toward the Colorado River, depositing Colorado Plateau souvenirs - rocks, logs, silt, fragments of petrified wood - on its banks and in the Colorado River. From our camp on the Colorado River, Ed Janik and Bill Persons take an Osprey down to the Little Colorado River confluence, where muddy water stains the mother river a chocolate brown. An experienced expedition volunteer who lives in Phoenix and works at a high-tech company, Janik helps Persons check fish-monitoring equipment. The Little Colorado is the richest known spawning area for humpback chubs, and scientists often helicopter down here to monitor the fish at one of several Little Colorado "fish camps." In the summer, state and federal scientists net juvenile hump-back chubs here and gently transport them in barrels via helicopter to the top of the plateau. From there, they're chauffeured to a New Mexico fish hatchery, where they're kept in warm water and fed for a year. The next summer, the tagged fish are chauffeured back to Arizona and released in Shinumo and Havasu creeks, two warm tributaries of the Colorado River in the Grand Canyon. Since the program began in 2008, about 1,400 fish have been "translocated," with a nearly 100 percent success rate, thanks to gentle handling, Van Haverbeke says.

Tom Bean, Van Haverbeke, volunteer Anya Fayfer and I hike up the Little Colorado to take Persons and Janik sandwiches and cookies. As they eat, the Little Colorado's banks begin to swell with silty water. Thunder's basso profundo warns us of a serious storm. Avoiding quicksand, we hike past layered sandstone rich with salt. Downstream on the Colorado River, rain washes over sacred, centuries-old Native American salt mines. In the evening, a giant boulder calves off a canyon cliff and careens into the Colorado River.

A few hours later, boatman Perry navigates the Osprey through roiling holes in the swelling river. Van Haverbeke checks the trammel net, and Perry steers the boat back toward camp. The fog is so thick, Perry's light is useless, so he navigates the rapid in the dark. In the blind, fog-thickened night, he avoids the deadly boulder and returns safely to camp.

The Little Colorado is running at 8,000 cubic feet per second now, doubling the flow of the big Colorado River and washing countless young humpback chubs downstream to an uncertain future.

As the Colorado River swells with muddy water, it threatens to wash away the expedition's kitchen on the beach. In the rain, we take the kitchen apart and relay pots, pans, tarps, food, tables, chairs and dishes to safer, higher ground. Van Haverbeke and Osterhoudt, a former medical secretary who changed her life to become a river biologist, dash into Perry's Osprey and quickly dismantle the trammel net in seething dark water.

In the morning, the sky is blue and the colorado river is the color of dutch cocoa. after hours of hoop-net collecting and fish monitoring, the science expedition drops us off near phantom ranch, then floats downriver.

As I hike out of the grand canyon, i take one last look at the colorado river. i think back to an earlier conversation with dave uberuaga, the superintendent of grand canyon national park. he described humpback chubs as part of the grand can-yon itself. but how do you explain the plight of a creature hidden in waters at the bottom of the canyon to the millions of people at the top of the canyon?

A canyon wren sings. i'm standing on a sandy ledge, and the river is so far below me i can't hear its roar. down there, i know, the scientists are setting their nets, looking for humpback chubs in the quiet places.

POSTSCRIPT

Seventeen days after it left lees ferry, the scientific expedition ended at pearce ferry, near lake mead. The crew had captured and monitored hundreds of humpback chubs, including 42 young fish that had traveled to and from the new mexico fish hatchery and were thriving in their new homes.

As i write these words, the scientists have yet to complete the input-ting and crunching of the data that will reveal insights into the condition of the grand canyon humpback chub populations.

Randy van haverbeke offers an educated hunch: the populations, for now, are stable. The species remains on the endangered list, though, and its long-term future is uncertain.

For more information about humpback chubs and the scientific studies that will help inform the u.s. department of the interior as it decides on future water releases from glen canyon dam, visit the websites of the grand canyon monitoring and research center at www.gcmrc.gov and the glen canyon dam long-term experimental and management plan environmental impact statement at http://ltempeis.anl.gov.