SOS for alewives!
Written by Chicago Tribune   
Sunday, 22 January 2006 10:05

With a series of new studies confirming the worst, Lake Michigan fishery managers have begun a drastic plan to save the fish species whose absence they believe would crash the lake's ecosystem. The alewife.

There was a time when Lake Michigan was stuffed to the gills with the Atlantic invader, which washed up on beaches by the smelly ton. As strange as it may sound, fishery managers now fear a downturn last year has left the lake with too few.

Biologists blame the change on the Chinook salmon of the Pacific Northwest. The most voracious fish in the lake. The fish that feeds in the same water level as alewives. The very fish they've stocked since 1967 to hold the alewives in check.

Alarmed their decades-long plan may suddenly be working too well and believing the Chinook have taken to breeding on their own, fishery managers said they'll stock 1 million fewer in their annual release this spring.

"The system is compensating at such a quick rate," said research biologist Randy Claramunt of the Michigan Department of Natural Resources, "and not in a way that we particularly want it to."

Much about life in the lakes is a mystery, fishery experts said. And though neither the alewife nor Chinook is native to Lake Michigan, their presence represents its new reality, in which stocked fish are pitted against invasive species to battle in the fish tank that was once a vibrant Great Lake.

At the heart of this new ecosystem is the Chinook salmon.

A $4 billion commercial and sport fishery has grown up around the Chinook and other big fish that eat alewives.

So the alewife must be saved.

It's arresting to realize, when you really grasp it, that most fish in our inland sea aren't from here and that nobody fully understands how they interact with one another.

Lake Michigan once had a food chain so simple a 5th-grader might draw it. (Lake trout eat forage fish that eat tiny things that eat plankton.)

Ecologists said the lake's ecosystem has morphed into a complex web involving a dizzying cast of scaly immigrants, natives of waters from Latvia to Afghanistan, plus a smattering of game fish from elsewhere brought in for good measure.

Among the relative newcomers are Chinook and Coho salmon and brown and rainbow trout.

The trout were introduced first for sport fishing in the late-1800s. The Coho and Chinook were bred with hopes of curbing alewives, and the Chinook at least fulfilled fish managers' wildest dreams.

Local fish--trout, chubs, whitefish and the like--have been reduced to despairing lives in far-flung pockets of the lake, perhaps to be rehabilitated later, maybe.

But the alewives and Chinook are fighting terrifically to stay.

The alewives came first, blundering up the St. Lawrence River in the 1940s. Their only plausible native threat on arrival were lake trout, big, ancient, deepwater fish, which by then were dying off thanks to invading lampreys and a thiamin deficiency.

Natives of Newfoundland, the alewives since their arrival have wandered the lake in great shimmering assemblies, looking for a smidgen to eat and settling in comfortably. Grasping opportunity in their troutless new world, they multiplied, overate and then themselves died--in shocking abundance and all over pricey lakefront real estate.

Keen to control this, fish managers started pouring in Chinook, reasoning they might provide a few nice days of fishing in a lake that only years earlier had been a wasteland of lampreys.

Chinook make nice-nice

It was learned at once that the big fish were hungry. More recently they've given hints at being amorous as well, the dim beasts mistaking a few chilly Michigan streams for rivers in British Columbia where they've begun to spawn, it is believed.

Prior to the introduction of salmon in the 1960s, alewives made up 90 percent of Lake Michigan's biomass, scientists estimated.

If the system was out of balance before, it is little better now.

After a favorable season in 1998, the amount of alewives in Lake Michigan weighed 132 million pounds--this for a fish weighing four ounces. In 2005, their cumulative bulk was more than halved to 55 million pounds, while the number of Lake Michigan Chinook marched ever higher.

A decade before this reversal, in the early-1990s, alewives had measured in the 220-million-pound range.

"These are wild fluctuations," Claramunt pointed out.

During measurements in the lake last summer, scientists found reduced numbers of alewives, and those they caught were scrawny. Even the populous Chinooks have been trimming down by eating them, ecologists said.

And it's not as though the lake would return to its earlier balance if the alewives and Chinook died off, Claramunt said, conceding that this was a point of some disagreement before delving into highly technical reasoning that included the phrases "social constructions," "assumptions" and "never return."

"Can we ever get rid of alewives in the Great Lakes?" he asked rhetorically. "Probably not."

Ecologists suspect there are a host of other fish on the sidelines, scoping for an advantage in the outcome of the salmon-alewife duel.

"I can't say what would happen, but I am confident that outcome would be undesirable," Claramunt said.

The management goal is to prevent any new dominance from developing.

Alewife decline mystery

No one is sure why the alewives are disappearing. It may be a lakewide drop further down the food chain of a shrimp-like critter called Diporeia. It could be that the alewives fared poorly last winter. Despite their North Atlantic heritage, alewives are fussy about temperature fluctuations. But lake scientists do know that fewer predators in the lake would make their lives simpler.

"Easiest to fix is reducing the predators," said Tom Trudeau, Lake Michigan program coordinator for the Illinois DNR. "Chinook is the target species because Chinook is the one species most dependent on alewives."

So until a resurgence of forage fish materializes, the greedy Chinook will be pared back, solving the problem for now but prolonging the lake's enduring love-hate relationship with the alewife.

Under a cooperative plan among Lake Michigan states, Illinois will stock 250,000 Chinook this year instead of the 300,000 last year. Wisconsin will reduce its annual restocking of 1.4 million by 300,000, and Indiana its annual 250,000 by 30,000, state managers said.

Michigan to cut most

Michigan will cut deepest, from 2.3 million in 2005 to 1.6 million this year, both because it stocks the most salmon and because spawning now occurs there naturally, managers said.

And while the alewives declined in 2005, it's not as if the Chinook, or king salmon, are yet following suit, even if they are a bit trimmer, fishery managers and Lake Michigan anglers said.

"They were more bountiful. Probably last year was the most bountiful king fishery in recent years," said Les Wood, captain of the D-BAIT-OR II in Waukegan harbor. "In the later part of the year, I noticed they were slimmed down a bit, but nothing to write home to mom about."

This year's fingerlings, still small enough that several would fit in a sardine tin, will be released in May, to wriggle off from rivers, harbors and shores into deeper waters and gluttonous prosperity.

They've already hatched in places like the Jake Wolf Memorial Fish Hatchery in Manito, Ill., where they swarm and fidget in a dozen fish tanks the size of canoes.

When large enough in early spring, they'll be transferred to larger pens outside (where local birds will marvel at their good fortune) and then be hauled to their ultimate freedom.

After that, Lake Michigan's stewards said, the future of the lake depends on how the Chinook interact with other lake life. But that's later.

"Everything looks real good right now," said Tom Hays, the assistant hatchery manager in Manito.

You need to login or register to post comments.