Spreading through the biggest intact temperate ecosystem on earth was an alien more hideous in this natural setting than any monster that ever slimed a Hollywood spaceship. But I still had three more days of blissful ignorance. It was July 27, 1994. My business in Mammoth, Wyoming, was finished. The sun was still high in the azure sky, and now, free as a June freshman, I was headed for my favorite place on the planet--Hayden Valley and the long, curling tail of the greatest inland cutthroat refuge in the world. "Hemingway," I noted in my fishing journal for that day, "had it right. Happiness is a trout stream all to yourself."

Well, not quite all to myself because Buffalo Ford gets lots of pressure. But I like to wade across the Yellowstone River and fish the east bank all the way to the falls at Sulphur Caldron. There's a little island halfway up where I can almost always be alone. The water is green and clean. You can see the big Yellowstone cutts cruising the shallows or sipping insects in the swirling eddies. At this time of year their gill plates and flanks are sunrise-red, but they have recovered from spawning and are in fine flesh--wild, robust fish mostly 17 inches and better. I know it sounds like a Jim Bridger tale, but sometimes the hatches here are so prolific the fish position themselves in the current with their heads slicing the surface and let the river fill them up. I've actually steered my fly into their open mouths. You have to see this place to believe how many fish there are. Scores of bird and mammal species depend on them.

This river, the 87,000-acre lake that feeds it, and the 59 trout-spawning streams that feed the lake comprise a vast ecosystem based on Yellowstone cutthroats--the interior West's analogue of the sockeye-based food chain of southwestern Alaska. The watershed and its evolving fauna have endured dredging by major hydrothermal explosions, damming and rerouting by earthquakes and volcanoes, the clutch and crumble of glaciers, and colossal fires that sweep out old growth on 200- to 400-year cycles. It's all a beautiful, complicated, self-mending machine, impervious to every insult in the universe save human tinkering.

Anyone who says Yellowstone cutts are not selective is wrong. Anyone who says they aren't as strong as rainbows is missing the point. My purpose is not to fight them but to join them, to watch their tail-waggling rise forms at the end of my cast or their rain-drop dimples as I fish down to them in the quiet coves, to feel them against a wisp of graphite, to cradle them in the coolness of their river while it piles against my ribs.

I come here to fish with my friends the otters and the minks, to be part of the energy flow that rises with the pungent steam of sulphur vents, cycles down around my shoulders with dancing caddises and falling spinners, rises again with the bald eagles and ospreys whose shadows sweep along the green and golden banks, recedes seaward with the migratory white pelicans who cruise stealthily through feeding trout with their heads tucked way back into their folded wings, gathers strength in the continent's biggest alpine lake, explodes into gravel redds and grizzly gullets high in the ragged Absarokas.

I come here also to watch the bison cross at dusk, the calves white-eyed and pumping hard to stay abreast of their mothers; to listen to the raucous shouts of Clark's nutcrackers and the discordant croaks of high, distant ravens; to hike in whiskey-jack silence through wildflowers and fragrant lodgepole forests new and old; to feel proud of being an American; to rejoice in the world's best example of wildlife management gone right.

On July 30 a lure fisherman, plying Yellowstone Lake just south of Stevenson Island, took a 17-inch, five-year-old lake trout. Knowing it didn't belong, the guide turned it over to park rangers. On August 5 another five-year-old lake trout of about the same size was taken between Breeze Point and Wolf Point. In September U.S. Fish and Wildlife Service gill nets turned up two smaller specimens, aged four years and two. Multiple year classes. Apparently these alien, highly piscivorous char were reproducing in the lake.

It wasn't an accident or an act of God. If the lake had been infected without human assistance, lake trout would have had to negotiate headwater streams (something they almost never do), swimming up the Snake River, crossing Two Ocean Pass, and dropping down the upper Yellowstone. Or these deep-water residents, rarely taken by avian predators, twice would have had to survive brutal, six-mile flights via osprey, eagle, or pelican from Shoshone, Lewis, or Heart Lakes where they had been unleashed in the 19th century when it was de rigueur for managers to play musical chairs with fish species. The Park Service has offered a $10,000 reward for information leading to arrest and conviction of the perpetrator(s) whose work it calls "an appalling act of environmental vandalism."

Such vandalism is "disgustingly simple," remarks fisheries biologist Robert Gresswell, formerly of the Park Service and now with Oregon State University. "We've had other illegal introductions in the park, and it happens in state waters all the time." In May 1985 Gresswell and his associates were doing routine spawning surveys in a Yellowstone Lake tributary called Arnica Creek when, to their horror, they encountered brook trout. That August the Park Service treated the stream with antimycin, a modern toxicant safer than rotenone and more effective in that fish can't smell it. As a precaution, treatment was repeated twelve months later.

IF EVER YOU GET AN URGE to thank the people who braved vicious opposition to show the nation what no-kill fishing can do for trout populations, who restored Yellowstone cutts from a state of collapse to main course in the greater Yellowstone food chain, I suggest you start with John Varley, the park's head resource manager. Varley is a professional conservator of wildness, a new-order biologist who never accepted the conventional wisdom that passionate advocacy of nature is somehow unscientific. Hanging from his office wall is a watercolor of a human index finger metamorphosing into an exquisitely-rendered Yellowstone cutthroat. Once, when there was room, it was on his desk pointing at him. He created it as a name plate with the idea of showing instead of spelling who he was and what he did. But I think the Park Service should commission him to paint it bigger and on the ceiling of the administration building.

To me the painting symbolizes the finger of enlightened, let-it-be management transferring the spark of life to an ecosystem killed by tinkers. When I look at it I see Superintendent Jack Anderson--unintimidated by a frenzied mob of concessionaires, politicians, and dump-stadia gogglers--daring to make a real bear of Yogi by weaning him from garbage to cutthroats, carrion, and whitebark pine seeds. I see Superintendent Robert Barbee defending natural-fire policy to chanting followers of Guru Smokey--"Barbecue Bob," the sagebrush rebels and know-nothing press called him. I see Park Service director Bill Mott standing up to an ignorant, superstitious Reagan White House in defense of wolf recovery and habitat acquisition. And I see John Varley defending his beloved cutts against incensed minions of fillet-and-release and brainwashed fish literati who kept saying "you can't stockpile harvestable surpluses."

When Varley heard about the first lake trout he was physically ill. He didn't throw up, but it was close. The day before--July 29--he'd been briefing the new superintendent on resource issues. "We were in the backcountry, overlooking Yellowstone Lake," Varley told me, "and, man, I was giving him the business about how well we had protected this ecosystem and how pleased we should be. 'We've got a lot of problems; but there's something that's museum pure.' And 24 hours later I hear about the lake trout. I just can't think of worse news. They could have said brook trout--well, that's bad news, but we can get around that. They could have said brown trout; they could have said almost anything, but not lake trout."

THE FACT THAT LAKE TROUT now exist in Yellowstone Lake has been widely reported, but not what that fact means for our first-born national park, a global treasure designated by the United Nations Educational, Social, and Cultural Organization as both a Biosphere Reserve and a World Heritage Site.

The lake sustains 80 percent of all remaining Yellowstone cutthroats (Oncorhynchus clarki bouvieri), and 90 percent of the park's river fish winter there. For their first several years of life the juveniles can't be found, and because they haven't shown up anywhere else, it's assumed they go out and down--precisely where the lake trout will lurk. The question is not what lake trout will do to the natives, but when. Wherever the species has been superimposed on wild cutthroat populations it has virtually eliminated them. There don't seem to be any exceptions.

For example, in 2,200-acre Heart Lake, tucked between West Thumb and South Arm on the other side of the continental divide, lake trout have about done in a large, piscivorous strain of cutthroat that evolved with six other indigenous fish.

Yellowstone cutthroats are smaller and even more defenseless. During their time in Yellowstone Lake they graze on scuds, chironomids, and plankton; they evolved only with longnose dace which inhabit the shallow, weedy bays and which they generally ignore. Longnose suckers, redside shiners, and lake chubs--none of which are major cutthroat competitors--were introduced long ago by bait fishermen or possibly by professional tinkers in an authorized effort to establish trout forage.

"If we don't do anything, everybody agrees that there's going to be a horrendous collapse," declares the park's resource naturalist Paul Schullery. "Within 20 years the cutthroats probably will be reduced 50 to 80 percent; and somewhere out beyond that they will be essentially gone. The ripples just go on and on. There's this big subset of the grizzly population that keys in on these trout. When the Craighead brothers were studying grizzlies in the 1960s they never once saw a bear take a fish." By 1975, when the effect of catch-and-release started kicking in, bear activity was being observed on 17 of 59 cutthroat spawning streams. Now bears work at least 55, and one research team observed a sow with cubs averaging 100 fish a day for 10 days. It's the only known situation where bears get significant nourishment from salmonids that aren't programmed to die after spawning.

While in the park, white pelicans get almost all their nourishment from cutthroats, consuming an estimated 300,000 pounds a season. In 1924 the tinkers looked upon these huge, ungainly birds and saw that they were bad. Not only did they eat trout, they served as vectors for trout tapeworms. So for the next eight years the Park Service squashed pelican eggs at the nesting colony on the Molly Islands. In a 1931 experiment to ascertain if trout tapeworms could be transferred to a mammalian host, a dedicated scientist named Lowell Woodbury swallowed 14 live ones; the study subjects perished in his digestive tract. Today the tapeworms still prefer pelicans and trout, and now the pelicans have rebounded along with the cutthroats which control their abundance rather than vice versa.

Ospreys underwent a similar resurgence after the tinkers quit using pesticides, after the conservators of wildness banned camping within a kilometer of active nests, and after the cutthroat population increased by a factor of 10. In 1988 there were 66 nesting pairs in the park; last year there were 100.

The park's bald eagles have fledged an average of 10 young a season for the past 12 years, with 17 in 1993 and 13 in 1994.

Since 1988, when I started fishing the Yellowstone River in the park, I've noticed that the trout have been getting bigger. When I first brought this to Varley's attention (before the lake trout showed up) he said: "As great as that fishery is now, recovery is still underway; we don't know where it's going." In 1973--the year Varley and his colleagues required that most trout caught in the park be released--they predicted the population shakedown would occur over the next seven years and that the effects of catch-and-release fishing would then be evident. They were wrong! Data collected on the Yellowstone River during the 1994 season revealed that the average size and the average age was still increasing.

But now, if the Park Service doesn't declare all-out war on lake trout, Varley knows very well where cutthroat recovery is going--down the tube. Even if it does declare war, neither the cutthroat population nor the trout-based ecosystem can ever attain their natural potentials. Lake trout are there to stay.

Might the lake trout be the progeny of fish unleashed in the golden age of tinkering that have just percolated along ever since? After all, unsuccessful introductions of rainbows and Atlantic salmon were made back then, and while there aren't any records of lake trout stocking, record keeping in those days was a notoriously casual business. Fishers of the lake--generally novices who don't excel at species identification--constantly report catching things like hornpout and bluegills, and park officials have been conditioned to just nod politely.

Maybe the tourists were right when they said they'd caught lake trout 20, 30, 40 years ago and more. It's a cheery thought, because it would mean that something is holding the invaders back, but I fear it's also wishful thinking. When I put my dream hypothesis to Behnke, he said: "No, I don't think so. When I used to work for the Fish and Wildlife Service in the late sixties we'd set gill nets all over that lake, some very deep. And we only got cutthroats. I think they've been in there 20 years max."

The most likely scenario is that some ecological illiterate who worshipped lake trout or someone who hated let-it-be managers (and there are plenty of both) caught some fish in Lewis Lake, popped them in a cooler, and drove the 30-minute trip to West Thumb. The lake trout planted more than a century ago in Lewis and Shoshone lakes came from Lake Michigan, and when lake-trout restoration got underway there, managers came to the park to collect eggs of the native stock. In the mid-1980s--just about the time biologists think the introduction was made--lake trout eggs were being stripped, fertilized, and shipped back to Michigan. Maybe somebody borrowed a few.

Solving the case is going to be tough. One wag fisheries advisor to the Park Service has suggested that it host a Lake Trout Derby/Celebration, then arrest the first two guys who show up. Investigators are analyzing tissue samples from the fish caught last summer to compare DNA fingerprints with specimens from hatcheries and regional lakes. And Gresswell is hoping to do some chemical analysis of the otoliths to see if he can find a sudden shift in ratios of oxygen isotopes. If he does, it will indicate that their owners switched environments, something you wouldn't expect lake trout to do on their own. If, on the other hand, he fails to detect such a shift, it would indicate what most biologists expect and fear--that the fish hatched in the lake.

During my research I came across a fictional account of illegal lake-trout introduction in Yellowstone Lake published in the Summer 1991 issue of Gray's Sporting Journal. A ranger drowns, and a maintenance crew at Grant Village helps look for his body with sonar. (This happened in real life, too.) During the search, big 30-pound-plus targets show up way down. They can't be cutts. Out comes the deep-sea tackle. Eventually, there's a hook-up and a prodigious tug of war until the head maintenance guy whips out a knife and lances the line. He then confesses that 28 years earlier he and the ranger had transplanted them: "'A bucket plumb full of little ones, two buckets of six inchers, and eight or ten monsters. Took canoes up to Heart Lake, and we stayed for three days. Used nets╔We wanted some lake trout out the back door, don't you see?'" For some reason these noble beasts are not reproducing, and the boss wants them left alone.

The more I dug, the more I was convinced I was onto something. Gray's had only the author's old address, and his last name, "Parks," struck me as fishy. The post office in his former town didn't have a forwarding address, and such a person was unknown to local guides, tackle dealers, newspapers, hook-and-bullet magazines, even an outdoor writer who lived on his old street. Finally, an insurance agent gave me the current address from a policy he had written on a boat--registered on Yellowstone Lake. Alas, Mr. Parks turned out to be a real, 37- year-old English professor who had guided for a concessionaire at Grant Village from 1979 through 1985, who hadn't heard about last summer's horrible news, and who never once tripped my sensitive BS alarm. "Did you ever hear anyone saying they had put lake trout in Yellowstone Lake?" I asked him.

After a long pause, Parks said: "I have to think about that. Something makes me want to say yes. No, I don't think so in Yellowstone Lake." Still, he allowed that he might have heard some talk, nothing too specific. He seemed genuinely upset about the threat to the ecosystem and eager to help in the investigation. He said he'd check with friends and get back to me.

HOW MIGHT AN ALL-OUT WAR on lake trout be waged? Some of the nation's best fish scientists, convening in a voluntary, emergency workshop, have kicked around ideas. There was talk about stocking triploid (sterile) sea lampreys which in fertile, diploid form invaded the Great Lakes and proved so effective in ridding them of their native lake trout stocks. You make triploid fish by shocking their eggs with chemicals, thereby giving them three sets of chromosomes rather than the normal two; but technology for mass-producing triploids and achieving a 100 percent success rate doesn't exist. All you need is two mistakes and you've got double trouble. Moreover, workshop chairman Jack McIntyre of Boise, Idaho, says he's not sure lampreys would concentrate on lake trout. "When we used to go electro-fishing in New York State I remember they'd even grab onto us."

"Did they drill you with their raspers?" I asked.

"No," he said, "we never gave them a chance."

Another interesting suggestion was to run bottom sediments through a big boat-mounted pump, spreading them over spawning beds. It takes just a dusting of silt to smother the eggs. The trouble is, there's not much lake bottom that doesn't look like super spawning habitat.

Workshop member Robert Behnke of Colorado State University thinks angling might be the most effective control. "Lake trout," he says, "are pretty vulnerable. If you can radio-tag a few and find where they congregate, you can put fishermen on them. Fishing pressure on [desired] lake trout populations is a big problem in places like Flaming Gorge Reservoir. Fishermen with fish locators really slaughter them. Gill nets would work well, too."

Chemical reclamation is out of the question. Antimycin is ruinously expensive, and there isn't enough rotenone on the planet. Five years ago the Utah Division of Wildlife Resources exhausted the world's supply of rotenone when it cleansed 13,000- acre Strawberry Reservoir of trout mongrels and exotic rough fish in order to make way for Bonneville cutthroats--the then-rare, salmon-sized survivors of an extinct, 50,170-square-mile glacial lake. (See "When Fish Managers Watch and Learn," Fly Rod & Reel, May-June 1992.) Not only is Yellowstone Lake much deeper than Strawberry Reservoir, it has a surface area nearly seven times as large.

The Great Lakes contingent of the workshop knew a lot about knocking the bejesus out of lake trout because they'd seen how the Indians do it. The good news is that they feel confident that the Park Service can keep ahead of the aliens, saving perhaps 80 percent of the cutthroat population, if it commits to expensive, labor-intensive "industrial-strength gillnetting." Gresswell, a member of the workshop, says this: "I think you can overfish any species, and if you put in a concerted effort on lake trout, you can keep those numbers way low. We have a good chance of maintaining the ecosystem at a level that will allow most of the processes to continue pretty much like they are now."

The big problem will be money. "You can only go to the trough so often," says John Varley. If the cutthroat population is allowed to collapse, all the magical places like Buffalo Ford just become cold, sterile scenery bereft of fishermen and fish-eating wildlife. Park visitation even by nonanglers will plummet. The new lake-trout fishery won't recover five cents on the dollar, and the torrent of money that sustains local tackle shops, motels, restaurants, and guide services, that built Jackson Hole and West Yellowstone, is going to dry up like tobacco juice on a stoked wood stove.

The biologists don't need any convincing, but the politicians do. On the Great Lakes even the dullest legislator could see what the alien lampreys were going to do to the native lake trout, but the resource had to collapse before the states would shake loose funds for serious action.

As Varley says, it's pretty hard to think of worse park news than lake trout among the cutts. But even as he was telling me the gory details, he was reporting the best park news that he or I could ever have imagined. Wolves were on the ground in Yellowstone; they'd be released in 72 hours. It had taken the conservators of wildness 20 years to pull this off, and no other initiative--not even no-kill trout fishing--had been more contentious. If Varley and his ilk can restore what the tinkers worked so hard to eliminate, what Teddy Roosevelt called "the beast of waste and desolation," what former Montana Congressman Ron Marlenee called "cockroaches in [our] attic," they certainly can prevail in a perpetual campaign of lake-trout suppression.

Yellowstone may have a few extra and therefore ugly parts; but at least now it has all its original ones. You can't say that about any other sub-Alaskan area of the United States. Returning wolves to America's oldest and best-loved park is "a profoundly symbolic act," to borrow the words of Renee Askins of The Wolf Fund--a private, single-mission group whose doors closed March 21, 1995, the instant the wolf-release-pen doors swung open. Despite the constant background noise from tinkers, wolf restoration means that the nation is now behind let-it-be management, that the conservators of wildness have finally prevailed. And if there could be better news for native trout than that, I can't guess what.

Author and Editor's Note:

Funds for lake trout suppression in Yellowstone Lake are desperately needed. If you would like to be part of saving the cutthroat-based ecosystem of greater Yellowstone, please make out a check to Yellowstone Fisheries Fund, enclose a note ear-marking it for lake-trout suppression, and send it to: Fisheries, Box 117, Yellowstone National Park, Wyoming 82190. If you have any information that might aid the Park Service's investigation of the illegal introduction of lake trout into Yellowstone Lake, please contact Pat Ozmont, Law Enforcement, Box 585, Yellowstone National Park, Wyoming 82190; 307-344-2120. Remember, there is a $10,000 reward for information leading to the arrest and conviction of the perpetrator(s).