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"Humpback Haven," by Julie Hammonds
This article was published in the September–October 2009
issue of Arizona Wildlife Views magazine. Support Arizona's award-winning wildlife magazine — order online.
Unique fishes survive and even thrive in the warm, turbid waters of the Little Colorado River.
Northeast of Flagstaff, the high chaparral plains curve like an overturned clay bowl beneath the sky, creating a parched landscape of sage and tumbleweed that shows more signs of geological activity than human presence.
The planet’s bones break the surface here, only to be carved and worked by erosion and rainfall, wind and flowing water (in those rare places where water can be found). Ridges rise above the plains, and canyons fall away into the earth. One of these is the most famous canyon in the world — the Grand Canyon of the Colorado. A less famous river carves another canyon and goes by two nicknames: the LCR or the Little C. On official maps, it’s called the Little Colorado River.
The Little C is a spring-fed travertine stream. Filled with calcium carbonate that gives it the color of sky-blue chalk (when silty runoff isn’t turning the water chocolate brown), the river shimmers in sunlight between steep canyon walls. The Little C is 315 miles long, from its source near Mt. Baldy in the White Mountains to the confluence where it flows into the icy green waters of the Colorado. Dry much of the year where U.S. Highway 89 crosses it at Cameron, Ariz., the Little C is revived at Blue Springs, some
13 miles above its confluence with
Hidden in these silky cerulean waters, miracles: desert fishes, superheroes of survival. How do they live, find food, spawn successfully, in this turbid water with its seasonal floods? How do they endure the heat and glare of high summer, when water temperatures may exceed 70 degrees?
Biologists have been studying the fishes in the lower 1,200 meters of this remarkable river since 1987, amassing a treasure chest of data about how native fishes have adapted to this strange environment. Their work is helping scientists back at the lab anticipate what may happen in the future. Because it is the best guess of people who have studied desert fishes for decades that time is running out; even for these superior survivors, extinction in the wild is not a distant possibility, but a reasonably foreseeable outcome.
All in a Day’s Work
Biologist Brian Clark is kneeling at a measuring board, holding a wriggling humpback chub. Before setting this fish on the board, he splashed water onto the wooden surface to cool it down. It’s May, and the air temperature is climbing toward the high 90s. “Can’t be too careful,” he says.
Clark’s duty post today is a flat rock beside a glowing blue river; instead of office walls, his view is a golden canyon beneath a northern Arizona sky the color of turquoise. On such a day, it’s easy to envy a field biologist. But this is not a cushy line of employment. It’s common for workdays to start before dawn or end after midnight (or both). Camps provide few of the comforts of home. Field seasons can mean weeks spent far from family. But Clark enjoys
this part of his job. “It can be trying,”
he says. “But what isn’t, that’s worth doing?”
Working quickly, the Arizona Game and Fish Department biologist bends over the fish, his nose nearly touching its shining green scales. He calls out the fish’s measurements to his assistant, Luke Avery, a volunteer from Flagstaff who is finishing a master’s degree in fisheries. When the fish flaps its tail, Clark murmurs to it, encouraging the fish to stay calm.
Lifting it in water-cooled hands, Clark calls out the fish’s sex and looks to see whether it has parasites. (It doesn’t.) After taking a reading to test whether the fish has been tagged before, Clark reaches for the tool he will use to slide a Passive Integrated Transponder tag the size of a grain of rice through the shining white skin into the fish’s pelvic cavity. For the rest of its life, this fish will be known and followed, sharing its movements and life history with a group of people who care very much about the welfare of its species.
Clark is the principal investigator on the “Little Colorado River Lower 1,200 Meter Hoop Net Monitoring Project.” Ongoing since 1987, the project provides an index of all the fish species present in the Little C, yielding data about how abundance of native species is changing over time. Natives found in the Little C include flannelmouth sucker, bluehead sucker and speckled dace, in addition to humpback chub.
The project uses 13 nets constructed from a fabric of coarse, sturdy mesh stretched over a framework of circular hoops. These particular nets — each one measuring 16 feet long and more than 3 feet across — have seven hoops. When waterlogged, the nets are so heavy it takes two people to pull one from the chalky water and set it down on shore.
For this project, nets are pulled once a day for 25–30 days in the spring. With the exception of a break in 2000–01, biologists have been setting the same type of nets in the same locations every year for the past 22 years. A timeline like that yields a mother lode of data scientists can work with all year long, summarizing how one year’s data compares with information from previous years; confirming trends observed in other projects (see sidebar, “A Cooperative Effort”); even feeding and calibrating computer models developed by the U.S. Geological Survey as part of the Glen Canyon Dam Adaptive Management Program — all in an effort to support these precious populations of native desert fishes.
The Humpback of the Little C
The humpback chub, that Quasimodo-like species, is the primary focus of all this effort. Its distinguishing characteristic, a large hump behind the head, is a puzzle. Scientists used to think it acted as a barrier to passing water, forcing the fish’s head downward toward the bottom of the stream in a natural feeding position for picking up algae. Now there’s speculation the hump is a defense against attacking herons or ravens, but nobody really knows.
These fish are strong swimmers with large, powerful fins, marvelously adapted to turbid, fast-flowing waters. One thing biologists have discovered during the Lower 1,200 Meter Project is that if these native fish make it to adulthood, they can live a remarkably long time. With fish first tagged 22 years ago still being caught, it’s estimated humpback chub can live as long as 30 or 40 years.
On the federal list of endangered species since 1967, this fish is found in only one place in Arizona: on the Little C, and in adjacent portions of the Colorado River. Populations also still exist in Utah and Colorado, but for a fish once common along the entire length of the Colorado River, the current, limited range supports numbers far below historical levels.
It wasn’t always this way. Until dams tamed the Colorado in the last century, this was a big, sun-warmed Western river. But the dams release clear, cold water. Under these conditions, nonnative fishes such as rainbow trout thrive. But native fishes adapted to free-flowing, wild Southwestern rivers can’t tolerate the clear, chilly waters.
On the other hand, “The LCR is a refuge for rearing young humpback chub,” says Andy Makinster, who is Clark’s supervisor on the Lower 1,200 Meter Project. He explains these fish require warm water to spawn, incubate eggs and perform the other steps necessary to complete their life cycle. “The only water temperatures that are suitable are in
Native desert fishes face a variety of challenges in addition to dams and their effect on water clarity and temperature. One of these challenges is competition with, and predation by, nonnative fish. Along with native fishes, the hoop nets along the Little C also regularly yield fathead minnow, channel catfish, black bullhead, red shiner and common carp, showing a minimal but possibly important presence of these nonnatives. Some of these species prey on the native fishes.
In 2008, nonnatives species made up less than 3 percent of the total catch during the project. Still, biologists are keeping close watch on these intruders. So far, they think conditions in the Little C, including high turbidity and salt levels plus cyclical flooding, are keeping a lid on these fish, which are adapted to more stable water conditions.
And how are humpback chub doing in the Little C? According to data provided by the project, Makinster says from 1987 through the early 1990s, numbers of humpback chub declined. But over the past few years, that trend has turned. The U.S. Geological Survey reported a 50 percent increase in the number of humpback chub from 2001 to 2008.
Several reasons for this improvement are possible. A drought has warmed waters released from Glen Canyon Dam, creating more favorable conditions in the Colorado River. Also, a department project to remove nonnative trout from the Colorado around its confluence with the Little C may be having an effect.
The ability to accurately gauge how endangered humpback chub are doing is one reason the Lower 1,200 Meter Project is so valuable, according to Makinster. “It’s so long-term that when you see increase or decrease on a two- or three-year basis, you feel confident the numbers might be real,” he explains. “Because the effort has remained similar — sampling protocols are unchanged throughout the entire term of the project — your decision-making confidence increases.”
What Does the Future Hold?
As technology evolves, scientists are exploring new ways to track the fishes in the Little C. One promising possibility is the use of stationary PIT tag antennas. Affixed into the riverbed, these don’t need a human operator to read the tags of fish that swim within a few inches of the antenna. Batteries charged by solar panels power electronic tag readers that are connected to the antennas. The entire system can run day-to-day without human assistance. Eventually, data collected by the tag readers may be transmitted up onto the canyon rim and thus to Flagstaff, allowing scientists to track fish from their desks.
No matter how the technology evolves, Makinster and others consider the Lower 1,200 Meter Project important to the long-term survival of humpback chub. “The better we get at understanding humpback chub and their environment and what improves things for them, the better their chances are,” he says. “We’re still learning things. The more we know about them, the more we can do for chub and other native species.”
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