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Unnatural Selection

Pollution, progress, and good intentions have caused drastic changes in the fish population of Lake Michigan over the years. It may be too late to restore it to its natural state, but should we try?

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Once there was a fishing hole in the upper midwest that fell on very hard times. Too many fishermen had taken too many fish out over the years, and then a newly installed culvert let some aggressive fish from other ponds in and they started taking over. Before long practically nothing was swimming in the old fishing hole but ugly foreign fish, some big and some little, and hardly anybody wanted to fish there.

The local conservation officers got together and decided that this was a shame and something would have to be done to entice the fishermen back. They found a poison that would get rid of the large nasty foreign fish and decided to temporarily stock big fish from elsewhere, hoping they would feast on the little junk fish infesting the pond and its beaches. Meanwhile the conservation officers would try to get the native fish reestablished so they could take over when the big, stocked fish had thinned out the invaders sufficiently. If all went according to plan, the fishing hole could end up back where it started, as a popular fishing spot full of healthy native fish.

A funny thing happened on the way to the balance of nature, though. It turned out that the fishermen were crazy about catching the big fish stocked to eat the nasty little fish. In fact, they were so enthusiastic about them that an entire new sportfishing industry sprang up, bringing huge numbers of people to the shore, generating new jobs, and reviving local waterfronts. Suddenly the conservation officials found themselves running what amounted to a highly successful "trout pond" (though the fish everybody wanted to catch weren't actually trout): the more big, exotic fish they stocked, the more people came to the pond to catch them (and the more money they deposited in the local economy). In fact, fishermen started worrying that there might be a shortage of the big fishes' food supply: those nasty little foreign fish the conservation officers had been trying to get rid of in the first place.

Nowadays the conservation officers find that their original idea--stocking the big fish temporarily--is, well, problematic. The anglers and the charter-boat captains ferrying them out into the pond naturally get upset about the idea that the stocking might not be permanent; after all, they say, the old fishing hole never attracted as many anglers in the old days as it does now. Other folks, though, want the original plan carried out: the pond, they say, should be restored as closely as possible to a natural balance of native species.

The conservation officers are caught in the middle. Can the old fishing hole ever get back to what it was? And if it can, should it? And if it should, how to do it? And is there any way that won't make a whole lot of folks unhappy?

This particular fishing hole means a lot to a great many people. You know it as Lake Michigan.

To understand how Lake Michigan got into this predicament we need to go back a ways. In the 19th century the lake teemed with fish of all sizes and descriptions and supported hundreds of commercial fishing boats that reeled in lake trout, whitefish, and perch by the ton. The supply of fish seemed inexhaustible, just as the great white pine forests surrounding the lake seemed to go on forever.

The fish weren't, and the forests didn't. By the early part of this century, the annual catch was steadily declining. Besides the rapacious fishing and the destruction of habitat through dam building and marsh draining, another factor started having a devastating effect on the lake trout and other larger fish: the sea lamprey. These parasitic beasts had made their way into the upper Great Lakes via the canal that was dug around Niagara Falls, and they found Lake Michigan trout easy prey.

Throw in the increasing pollution of the lake's shallower, warmer areas, and by the 1950s the entire ecosystem was in tatters. An opportunistic little saltwater fish called the alewife had followed the sea lamprey in and, with the trout and other top predators gone, found paradise. With no natural predators, and breeding more aggressively than the native perch and other smaller species, the alewives simply took over. By the mid-1960s, experts estimate, at least two-thirds of the fish in Lake Michigan by volume were alewives. In the late 60s, when the alewives had eaten and bred themselves into a state of overpopulation, they suffered a series of massive die-offs that made their small, silver carcasses familiar nuisances to beachgoers around the lake.

Back in the 1950s the states around the Great Lakes had established, with the blessing of the federal government, the Great Lakes Fishery Commission to try to find some answers. The commission's researchers soon found a weapon against the sea lamprey, a chemical that could kill their young in spawning streams without poisoning everything else in the water. Annual "lampricide" efforts began, and by the mid-1960s lamprey were on the decline.

The lake's food chain was so thoroughly out of whack by then, though, that it was apparent that just removing the lamprey wouldn't make the lake bounce back, at least not in the lifetime of anybody then thinking about it. Besides, the alewife situation made the headlines and the nightly news in the summer of 1967, when the die-offs forced the closing of Chicago and other beaches, and fast action was needed.

The interim solution, the states' conservation agencies decided, was salmon. Certain species of salmon native to the Pacific Northwest, notably coho and chinook, were closely related to the native lake trout and were known to enjoy alewife alfresco. Indeed, rainbow trout, also known as steelhead salmon, had been introduced in Lake Michigan in the 19th century and had survived in small numbers. Also, coho and chinook were popular sport fish, so the cost of stocking might be recouped by attracting sport fishermen to catch them after the salmon had fattened up on the alewives. Meanwhile, stocked lake trout would hopefully be able to reestablish themselves as the salmon cleared out the alewives. Similar plans were made and carried out in the other Great Lakes.

But as it turned out, the salmon--particularly the chinook--attracted more anglers than anyone foresaw. By 1985 the fishery commission estimated that sportfishing overall on the Great Lakes had become a $4-billion-a-year industry, with lakes Michigan, Erie, and Ontario generating the bulk of those revenues. By the early 1970s there were hundreds of charter boats on Lake Michigan operating from April through October; more than 200 were licensed in Illinois alone. The eager hordes of salmon fishermen "really kind of took the [state] agencies by surprise," says Terry Yonkers of Great Lakes United, a coalition of environmental activist groups around the lakes.

The sportfishing boom has in turn helped spark a boom in waterfront development around Lake Michigan: millions of dollars have been invested in new marinas and charter-boat docks. Groups such as the Great Lakes Sport Fishing Council, with chapters in every bordering state, now actively lobby for state spending on the stocking programs, and the agencies have responded: a fishery commission study put the states' spending on exotic salmon stocking around the Great Lakes at more than $75 million between 1966 and 1988.

While that may be "an awfully expensive way to run an ecosystem," as Illinois state aquatic biologist Ellen Marsdon has put it, sport fishermen argue that our tax dollars are being well spent, given all the economic activity inspired by the large "trophy" salmon. The states also get some of the money back directly: while the Illinois Department of Conservation spent $330,000 on salmon stocking in the fiscal year that ended June 30, it realized almost $200,000 in the Chicago area alone by selling special $2 "salmon stamps" on daily fishing licenses.

The long-range goal of the state, federal, and Canadian agencies managing the Great Lakes ecosystem, as codified in the official goals of the Great Lakes Fishery Commission, is re-creating "healthy aquatic ecosystems in the Great Lakes that are based on foundations of naturally reproducing fish populations."

That goal now seems distant at best. The most obvious reason is the great success of the salmon fishery, but there's another that may be just as important: the absence of a viable native alternative. Efforts to reestablish the lake trout--the next step in the grand plan to restore Lake Michigan to a natural balance--have so far failed, though other native species such as whitefish, yellow perch, and chub have made remarkable comebacks. Moreover not everybody is convinced it's worth the effort to bring back the lake trout.

The U.S. Fish & Wildlife Service (USFWS) has been raising and stocking lake trout in Lake Michigan since 1958, and the stocking "has produced a fishable population of adults," says Marsdon, who is director of the state's Lake Michigan Biological Station. "The missing link, though, is reproduction. Why aren't we getting it?" Researchers are now finding, Marsdon says, a few places where the lake trout are laying eggs, such as a breakwater off the Indiana shore. They have also found pregnant lake trout "full of eggs and ready to spawn" at such natural spawning sites as a reef 14 miles off Waukegan. But what they cannot find is evidence of "recruitment," growth from eggs to fingerlings.

This is all the more striking because some of the more exotic salmonid species, including rainbow trout and chinook salmon, are successfully reproducing in the lake. There are a number of theories about why the lake trout aren't:

Federal researchers have documented that toxic pollution kills some newly hatched trout fry. "But it's not clear that it's enough of a problem to be the problem," Marsdon says.

Competition from exotic species could be a factor: alewives eating hatchlings, for example, or competing for food with young lake trout.

"The [natural] spawning habitat may be too degraded," Marsdon notes, the natural reefs covered with silt from dredging or fouled by pollution. The recent discovery of spawning on the artificial breakwater tends to support that idea and give hope that the trout can adapt to altered conditions, she adds.

And one possibility, perhaps more likely than any other, Marsdon says, is that "there is no single major cause."

Some years ago the USFWS established several large lake trout refuges containing potential spawning reefs in the Great Lakes, including Lake Michigan, where the stocking has been concentrated and where fishing for lake trout is prohibited. Since trout take several years to reach sexual maturity, "We've all got our fingers crossed about seeing the first year-classes this year or next year," Marsdon says.

Restoring naturally reproducing lake trout is a high priority for those who believe the lake's ecosystem should be moving toward restoration. Terry Yonkers says, "We definitely would like nothing better than to see a sustaining population of lake trout. There are signs of movement that way, and it's critical." Only if the lake trout are on the way back, he adds, can we credibly talk about phasing out the exotic salmon stocking.

Curtis Sliwa, Illinos chapter president of Salmon Unlimited, a sport fishermen's group, has watched all these efforts with growing skepticism: "I don't think I'll see [naturally sustaining lake trout populations in Lake Michigan] in my lifetime." Ed Michael, regional vice president of Trout Unlimited, replies, "It took a long time to kill them off, and it will take a long time to bring them back," though he adds that he believes more lake trout reproduction is occurring than has so far been documented by researchers.

In any case, Sliwa says, when it comes to supporting a multibillion-dollar sport fishery, restored lake trout cannot replace stocked salmon: "It's just not a fighting fish the way a chinook salmon is. I caught a 22-pound lake trout recently, and it was like I had a tire on the end of the line. I don't think people are going to go to the trouble and expense to fish out there if lake trout is all they'd be going for." The fishery commission's Randy Eshenroder agrees: "The lake trout can't become the same kind of centerpiece of sportfishing the way the chinook is now, because of human expectations. At the moment, ecosystem importance is not as important as angler demand" in decisions by the states about managing the lakes.

Longtime Chicago charter-boat captain Jerry Pabst, waiting out stormy weather at Diversey Harbor one day in July, agreed with that assessment of the lake trout as a sport fish but added a qualifier: "Anglers do appreciate the lake trout, and it will fight like hell if you catch it near the surface, but that takes luck--they're normally a deep-water fish." If caught there lake trout won't fight much, but salmon are regularly found near the surface. Besides, Pabst says, lake trout can be hard to track down: they spend only the hot summer months concentrated in certain deep areas, and in spring and fall "they scatter all over the place and you can't target them." So if the other salmonids were absent, the charter-boat season would be shortened considerably.

Michael disagrees: "People have this notion that fishermen will only be interested in chinook salmon. I challenge that assertion--that's somebody with a vested interest talking." Yonkers points out that seeking salmon and trout from the deck of a charter boat isn't the only way to fish. "Maybe if we lose some of that deep-water fishery," he says, "we'd gain in the warm-water fishery," such as perch and bass fishing near shore.

Rich Hess of the Illinois Department of Conservation has doubts about lake trout on another score: "The million-dollar question is, could the lake trout by themselves do the job of controlling the alewives? I don't think so myself, because the alewife is such a widespread species. The lake trout prefer deep, cold water." So eliminating one exotic species--the salmon--might inspire a comeback by the more notorious one, the alewife. Or it might not: even if stocking were halted, the chinook and coho might survive in smaller numbers and help keep the alewives down.

No one involved with the Lake Michigan fishery has any illusions about the lake returning to a state of nature anytime soon, if ever. For one thing, chinook and coho salmon are now spawning in certain Michigan rivers (something fish managers thought impossible when stocking began), as are the rainbow trout and, in small numbers, pink salmon. The lamprey and alewives, though much reduced in numbers, are still present and being kept down mainly by artificial means (lampricide treatments and salmon stocking). "The ecosystem is changing, and we can't say into what," Yonkers says. "It won't be the state of nature, though."

"There are always more invaders," Michael points out. "Now there's the zebra mussel, and there's bythotrephes cedestroemi [unofficially known as the "spiny water flea"], and on and on. I do think we will cut down on invaders, now that more is known about how they get here, but there will always be exotic introductions one way or another." Marsdon agrees: "The goal is to emphasize native stocks. Total elimination of all exotics seems implausible." With all the foreign species, competing pressures from different interest groups, and ongoing toxic pollution, "I would say we're going to be managing this lake in perpetuity," Hess says. "It's hard to see how we could ever get back to the original conditions."

Environmental groups like the Lake Michigan Federation and Great Lakes United are increasingly pressing for the states to at least move away from the deliberate planting of exotic salmon, however. Michael says, "It's what the public is going to demand. More and more people are taking an interest--it has to do with the perception of beauty in systems."

But at the moment the idea of eliminating the stocking of exotic salmon seems far from the minds of the state officials who would make that decision: asked if any of the state agencies are moving toward a focus on sustainable populations of native species, Eshenroder says, "Not that I know of." Hess agrees: "I would say we're not [moving toward the end of salmon stocking]."

Charter-boat captains like Pabst are scornful of the idea. "Other than a few starry-eyed folks, I don't know who would support it," he says. "Not the states, or the towns, or the industry selling all the boats and tackle. The average customer going fishing isn't even aware of all this, especially since it's all theoretical anyway. What's the point of it? If [environmentalists] love lake trout, fine, we've got millions of 'em. Why would someone want to deprive the citizens of this great fishery just to satisfy some scientific utopia?"

Some experts, though, believe that a food chain dependent on stocked predators is inherently unstable over the long term. University of Wisconsin researcher James Kitchell explains that stocked fish populations inevitably contain less genetic diversity than wild populations, and so may be more vulnerable. "Stocked populations may be inherently less adaptable to natural variations," he says, like weather and disease. "This put-and-take fishery may be weakening the gene pool of our top predators," Yonkers says. Michael predicts, "We will find over time that the nonindigenous species are inherently less adaptable and less viable."

That point is still open to debate, however. Recent die-offs of chinook salmon could be due to farm-raised fish being less resistant to disease, "but we don't have enough data yet to tell," says Myrl Keller of the Michigan Department of Natural Resources. "We're studying that question now." Another possibility is that they've been weakened by lack of food.

It seems salmon stocking has "done exactly what it was supposed to do," Yonkers notes: reduced the alewives to a tiny fraction of their numbers 30 years ago. As Hess remarks, "No one in our wildest dreams imagined we might start running out of alewives." And yet from the salmon fisherman's perspective, that may be a problem. Starting around 1988, Lake Michigan chinook began dying in large numbers--some estimates put the dropoff in chinook catch in Michigan waters as high as 90 percent between 1988 and 1992. It turned out chinook started washing up dead on beaches because of bacterial kidney disease, or BKD. The more interesting question is, what caused the BKD outbreak?

Some experts, like Kitchell, argue that the disease spread through the state fish hatcheries because conditions there "are perfect for such a disease to spread quite rapidly." Indeed, a virus swept through federal lake trout hatcheries in 1988, wiping out an entire year-class of trout fry. And in 1991 the Michigan Department of Natural Resources destroyed its existing chinook hatchery stocks and started fresh with eggs from Lake Ontario, to purge BKD from its hatcheries.

Other researchers and state officials and many sportfishing groups, though, argue that the problem is an alewife shortage--a concept rife with irony for anyone who remembers Chicago bulldozers plowing up tons of dead fish on the city's beaches. Chinook salmon in Lake Michigan, they argue, have depended almost exclusively on alewives for food, and have been unable or unwilling to switch to other food sources as alewives have been replaced by perch and chub in the lake's food chain. BKD is a fairly common disease, they point out, that doesn't normally kill healthy adult fish; the sudden outbreak in Lake Michigan, this theory goes, is a symptom of the chinook being weakened by lack of food.

Pressure from sportfishing associations like Salmon Unlimited and the Great Lakes Sportfishing Council led Wisconsin in 1990 to place new limits on commercial fishing for alewives (which are used for cat food). And starting this year Wisconsin, Illinois, and Indiana have agreed to reduce their chinook stocking by 25 percent to let the "forage base" recover. Wisconsin Department of Natural Resources chief Lee Kernan says flatly, "I think we've overstocked the lake." Michigan officials, though, have questioned the forage-base theory, and starting in 1990 they sharply increased the number of chinook they stocked to replace those that were dying.

Keller argues that little systematic field research has yet been conducted on the feeding habits of the predator fish: "All the thinking before about the forage base and the salmonids [salmon and trout both] was sheer speculation. We need the knowledge so we can manage on biological fact." To that end, Michigan is conducting studies of the diet of chinook in the lake, and preliminary results are that in fact "they will eat chub, and quite regularly," Keller says. So, he asks, "was the stress [that sparked the BKD outbreaks] a lack of forage? I personally don't think so."

The long-term question of whether the world's largest salmon pond has reached the limits of its capacity remains open. Perhaps this year's and next year's catch, along with the results of Michigan's studies, will provide some answers.

If there is a practical middle course to the management of the Great Lakes, it may be the one envisioned by Ed Michael of Trout Unlimited, who describes his group as "ecology-minded fishermen interested in self-sustaining salmonid populations." Though he acknowledges that this ecosystem has been permanently removed from its original state, Michael says, "Our efforts should be directed towards providing ecosystem balance and ecosystem health. Ecosystems with foreign agents are dysfunctional" and, he argues, in the long term inherently less stable. "I believe we wasted a lot of years and money creating what is ultimately a nonsustainable fishery."

Some stocking may always be needed, Michael says, to keep native species from dying out, and he believes that sustainable nonnative species (such as rainbow trout and possibly chinook and coho) have their place. But "way down at the bottom of my list," he says, "is a put-and-take fishery. I'm not an advocate of stocking solely for fishermen to catch."

The Great Lakes Fishery Commission is now leading an effort by the states, the USFWS, and Ontario to develop a comprehensive long-term plan for the Great Lakes fisheries. Known as the SIMPLE process (for Sustainability of Intensively Managed Populations in Lake Ecosystems), this effort has included workshops around the lakes in which all sides have had their say. Depending on the results of that project, and on whether the governments agree to carry out their recommendations, Lake Michigan could be a very different kettle of fish a couple of decades from now.

Art accompanying story in printed newspaper (not available in this archive): illustration/Tony Griff.

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