“One went south, we went north, one went straight out and we all hammered them. You used to come back with a cooler full of fish and it was just beautiful.”

Back in the day? That was 2002.

These days, the Sandy-B is the only charter boat still working in Harrisville. Beyer took her out 10 times last year, down from the usual 35-40 and barely enough to cover his fuel and dockage costs. Oscoda, which once had 12 charter boats, is down to two. Seven captains have closed down in the Port Austin-Grindstone City area. It's the same story up and down Michigan 's sunrise coast. Tawas. Presque Isle. Harbor Beach . Officials estimate that each Lake Huron port has lost more than $1 million in annual revenue from salmon fishing.

There are still some salmon being caught in the northern reaches of the lake, near the straits of Mackinac and in Canada 's Georgian Bay and North Channel . But for the most part, the salmon fishing days of Lake Huron 's main basin are gone.

That's because the prey species salmon and other predators depended upon – the alewife – collapsed. The big schools of fatty silver alewives simply weren't there any more, likely victims of invasive zebra and quagga mussels that scoured the lake's open water of critical nutrients, and the salmon themselves.

Their disappearance has upended Lake Huron 's food web and created an entirely new ecosystem, virtually overnight by biological standards. Less than a decade ago, Lake Huron was an artificial system where virtually all the key players from chinooks to lake trout to walleye were heavily stocked, prey species waxed and waned accordingly, and fisheries managers made little tweaks to keep everything humming. Now, Lake Huron 's open water – the pelagic zone -- is virtually devoid of life because the mussels have sequestered all the nutrients on the bottom and around the edges.

Deep-water dwellers like lake trout and near-shore species like yellow perch are reproducing with renewed vigor. Walleye, another near-shore species, have gone off the charts with one record year class after another. Unlike chinook salmon and alewives, all three are native to the Great Lakes .

“Whether this is a good thing or a bad thing depends on your personal view of what Lake Huron should be like,” said Jeff Schaeffer, a research biologist with the United States Geological Survey's Great Lakes Research office in Ann Arbor, Mich. “If you're a person who believes in ecological restoration and native species, you probably think this is really cool. If you're a walleye fisherman, this is something you've been waiting for your whole life …. If you are a chinook angler these changes have been devastating.”

Scientists from the surveys that use sound waves to determine fish populations to bottom trawling and creel surveys. Here is what they think: Changes at the bottom of the food web doomed the alewife, a Great Lakes intruder that became the main food source for salmon and a number of other predators. The demise of the alewife touched off a series of other changes that are still playing out, including the collapse of chinook salmon and the explosion of walleye in Saginaw Bay . In its simplest form, the story began more than 100 years ago, when alewives swam from the Atlantic Ocean into the Great Lakes in the late 1800s and eventually came through the Welland Canal , which bypasses Niagara Falls . They reached Lake Huron in mid-century, and by the 1950s they became so abundant in the Great Lakes that massive die-offs turned beaches into vast swaths of stinking fish carcasses. Salmon were introduced in the 1960s to control them, which they managed to do for nearly 40 years.

Angler Scott Draves shows off a pair of nice Saginaw Bay walleye he caught in April 2009. (Courtesy Photo)

But along the way, invasive species, native species and stocked species began to interact in ways no one predicted. In the late 1980s, zebra mussels first appeared in the Great Lakes , followed a decade later by quagga mussels, which colonize deeper waters. Both are thought to have arrived in ballast water from ocean-going ships. From there:

•  Zebra mussels trapped nutrients near shore and quagga mussels spread into the deep center of Lake Huron . Quaggas cleared the deep water by filtering out the small particles of plant and animal matter.

•  Those small particles were the food source for small shrimp-like crustaceans called daphnia, misis and diporeia, which rise off the bottom and feed by night in open water, then settle back to the bottom by day. Fish like alewives, whitefish and baby lake trout would feed on them when they migrated upward into open water.

•  Without food, diporeia and misis died off. That eliminated the mechanism for spreading nutrients up into the lake where alewives feed, thus trapping nutrients at the bottom.

•  Without the migrating crustaceans, alewives had little to eat in the pelagic zone.

•  In the 1990s, the millions of salmon that had been stocked in Lake Huron by Michigan and Ontario began to spontaneously reproduce, mainly in undammed Canadian tributaries, creating a much larger Chinook salmon population than anyone realized.

•  All those salmon devoured alewives, which were already struggling from a diminished food supply.

•  Hard winters in 2002-04 took a further toll on what was left of the struggling alewives. “What we know is that those three things together were an absolute slate-wiper for alewife and none of them are mutually exclusive,” Schaeffer said.

Without alewives, many chinooks moved on to more fruitful waters of Lake Michigan and Georgian Bay , while others grew emaciated and presumably died off. The 1.5 million chinooks Michigan 's DNR still stocks in Lake Huron each spring don't fare much better. The young fish don't head for open water until September, according to Jim Johnson, a Michigan DNR fisheries biologist in Alpena. In the meantime they hang around near shore looking an awful lot like alewives. In other words, they're food.

“We think most of the fish we stock are becoming prey to the things inshore that are looking for fish to eat – walleye, lake trout, cormorants. Their life history is all wrong for this new ecosystem.”

Michigan DNR biologist Ji He weighs a lake trout as part of a survey to determine lake trout abundance.

But the absence of alewives appears to be beneficial to several native species, namely walleye, yellow perch and lake trout. Walleye are reproducing at record levels and turning Saginaw Bay into an outstanding fishery that, for now, has better walleye catch rates than world-famous Lake Erie . Dave Fielder, a Michigan DNR biologist who helped write Michigan 's Lake Huron walleye recovery plan, had identified alewives as an impediment to walleye populations, suspecting that alewives preyed upon walleye fry. So the long-term plan involved heavy walleye stocking designed to beat back adult alewives and give the baby walleyes a chance to grow. Then the alewives were gone. Walleye numbers exploded and scientists realized just how profound an effect alewives were having on the native species. “It's very exciting to see the enormous magnitude of reproductive success in Saginaw Bay for walleye and yellow perch,” Fielder said. “What we hoped to achieve, I thought maybe in my lifetime or by the end of my career … happened in the food web almost overnight.” The 2007 class of walleye young was the biggest ever, Fielder said. The same was said of 2003, 2004 and 2005. Trawling surveys showeda 25-fold increase in walleye yearlings; for perch it was

closer to a 200-fold increase. Walleye anglers enjoyed the change, too: They caught seven times as many fish in 2006 as they did in 2002, according to the DNR, and walleye stocking has ceased entirely. Those are all wild fish.

“It's been going great guns this spring,” said Terry Walsh, a charter boat captain in Au Gres who once fished for salmon but now concentrates exclusively on walleye. “It's not hard to catch a limit of fish out there.”

Lake trout also seem to have benefited from the demise of alewives, at least in part because of an enzyme called thiaminase. Alewives are rich in thiaminase, and thiaminase causes fertility problems in lake trout. Without it, lake trout appear to be reproducing well.

“It all fits,” Fielder said. “Alewives are suddenly out of the picture, and the natives are benefitting. Things are really taking off.”

Dave Reid, the Lake Huron Management Supervisor for the Ontario Ministry of Natural Resources, said fisheries managers are beginning to realize that it may not be possible to sustain both a chinook-based fishery and one based on native species.

“Our job is to create as diverse a fishery out there as we can,” he said. “We are starting to realize we can't have everything ... It doesn't appear that chinook and some of those native species are compatible, because to have Chinook you need alewife as a prey base, but you can't have walleye and some of those other things when you have alewife.

“Previous fish community objectives did try to be everything to everybody, but I think we are coming to realize that we can't sustain a fishery with those native species and non-natives living in harmony. We really haven't come to grips with that. “

Many questions remain unanswered, and scientists will continue to monitor populations in an effort to understand a lake that seems to be imposing its own will.

Lake trout seem to be reproducing better, but they're smaller. Yellow perch are reproducing in huge numbers, but having difficulty reaching maturity because predators have turned to them for food. Prey species were expected to rebound when alewives crashed, but many haven't and there's still a possibility the alewives will return. Fisheries managers are re-evaluating stocking efforts and trying to see if there are better ways to do things in the face of shrinking budgets.

“Part of the problem is that things are a moving target,” Reid said. “Everything is shifting and we don't know what to expect out of the lake at this point.”

Part II: Lake Huron: Seeking new balance
Part III: Lake Michigan: Another shifting food web