Role Reversal on the Colorado

For about 210 miles in Arizona, the Colorado River below Glen Canyon Dam is infested with alien fish that threaten natives. So, to control the aliens and thereby test the feasibility of recovering the natives, the US Department of Interior has approved a two-year experiment that will be well underway by the time you read this. At Glen Canyon Dam the Bureau of Reclamation (BuRec) will fluctuate flows in order to expose redds and kill eggs. In a 9.4-mile stretch above and below the mouth of the Little Colorado River (which enters the mainstem 76 miles downstream of the dam) the US Geological Survey's Grand Canyon Monitoring and Research Center (GCMRC) will lead an effort to remove the aliens with electro-fishing gear, euthanize them with an anesthetic, then hand out the carcasses to local Indians to use as fertilizer. At Bright Angel Creek, 103 miles below the dam, the National Park Service installed a weir on November 18, 2002 that has been interdicting aliens as they enter what is believed to be their most important spawning tributary.

The aliens are wild, self-sustaining trout—virtually all rainbows in the 15 miles below the dam known as the Lees Ferry reach, virtually all browns at Bright Angel Creek and a mix, top-heavy with rainbows, near the Little Colorado River. The natives are chubs; you know, the "trash fish" your grandfather taught you to squeeze and toss into the bushes—in this case "humpback chubs," federally listed as endangered. The feds weren't always so protective of humpbacks. For example, 40 years ago, above what is now Lake Powell, they tried to eradicate them (along with bonytail chubs, razorback suckers and Colorado squawfish—all currently endangered) by applying 20,000 gallons of emulsified rotenone to 445 miles of the Green River and its tributaries. As one angler later told the Fish and Wildlife Service: "Everybody was tickled to death. There was so much chub and trash fish, [but] there was no trout."

Trout control on the Colorado outrages some sportsmen. "We cannot go back to the Garden of Eden," writes Mike Miller of the Colorado Fishing Federation in an action alert entitled Endangered Species Threaten Sportfishing. "You can poison all of the sportfish in the basin, and the evidence suggests it would have very little impact on recovery of the endangered species. . . . Millions of sportsmen's dollars are used on endangered species protection. This is a fact short-sighted, narrow-minded environmentalists never seem to consider. In the end, the alienation and disenfranchising of anglers will have a much greater negative impact on endangered species protection."

A more thoughtful and dispassionate analysis is offered by Terry Gunn, a dedicated conservationist entering his 21st year guiding fly fishermen at Lees Ferry and one of the best guides I've fished with. Not that Gunn is happy about the plan.

"I really have to question the science," he told me. "It's a shot in the dark, a supposition at best. I think the [rainbow] trout are getting a bad rap here; the predation rate on humpbacks is only .07 percent [of trout stomachs checked]. And there are so many other things affecting the humpback chub. Now they've got an Asian tapeworm."

Dave Foster, another highly respected Lees Ferry guide and conservationist, has worked here since 1988, fished here since 1966. Like Gunn, Foster does his homework and never shoots from the hip. "We're mixing our science," he declares. "We've got a flow regime aimed at reducing spawning trout and at the same time a very expensive program to eradicate trout at the mouth of the Little Colorado River. A few years down the road you're not going to be able to tease out which was the most effective method. I've always felt that what's good for the trout is good for the chubs." He agrees with Gunn that the fluctuations aren't going to hurt the trout at Lees Ferry, but that doesn't mean they won't hurt the fishing. "Anglers will do great in the morning," he says. "But then when the water rises in the afternoon [during peak demand] they'll be standing up to their nipples and casting to gravel bars that were dry the day before."

There are a few humpback populations above Lake Powell, but only about 2,000 adults survive in the lower basin, mostly in the Little Colorado River. Like the other seven native fish species once abundant in the 277-mile Grand Canyon stretch of the main Colorado, the humpback is a big-river fish adapted to flows that could vary between 2,000 and 200,000 cubic feet per second. Large fins allow it to sail through fierce currents. Small eyes protect it from swirling silt. So adept is it at sensing vibrations that it can pick off floating insects in water turbid enough to obscure your rod tip an inch below the surface. It has silver flanks, a long snout, a pencil-thin "wrist" before the tail, and the hump of a male pink salmon in spawning condition. When humpback fry, sweeping down from the Little Colorado, hit their traditional habitat in the dam-chilled mainstream they go into thermal shock and are easy pickings for predators. About 10 percent of brown-trout stomachs checked contain humpbacks; and, while humpbacks are found in the stomachs of only half to one percent of rainbow trout, there are so many rainbows that this could mean between 125,000 and 250,000 rainbows.

The Colorado squawfish (or "pikeminnow"), the bonytail chub, the razorback sucker and the roundtail chub have been extirpated from the park (though they still occur above Lake Powell). If trout predation continues at its current rate, the US Interior Dept. reckons the population of adult humpbacks could fall to 500 within the decade. Extirpation would likely follow shortly thereafter.

"I backed Babbitt's [1996] flood to restore beaches," says Gauvin, "and I got nasty mail from TU members, proclaiming that I wouldn't be happy 'til every trout in the Colorado was flushed into the Sea of Cortez. If we fight this, what will we say to Walleyes Unlimited when they complain about some coho recovery program in Oregon? Let's grow up. This is a problem we have to live with in these altered habitats where trout are a mitigation species. If the science is good, what business have we to be complaining about efforts to save a native species?"

Critics, including Gunn, Foster and a large element of the environmental community, say the science is bad. But the science hasn't happened yet. What is underway on the Colorado is called "adaptive management"—you try something, collect and analyze data, then see if you got results; if you didn't get results, you try something else. Basically, you do the best you can with the information you have. In 1991 adaptive management called for the stabilization of flows. This, reasoned managers, would be good for trout and chubs. Unfortunately, it was good for neither. According to best estimates, it quadrupled the number of trout (which is not the same as benefiting them). Concurrently, the humpback population started to fall off. Before 1991 - when flows fluctuated wildly - the trout fishery at Lees Ferry depended on stocking. Now it's self-sustaining.