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PBS Documentary Explores Lake Huron's Invasive SpeciesAgency: Natural Resources
April 15, 2010
As America prepares for another Earth Day celebration, public television stations across Michigan will telecast a documentary that shows how the Great Lakes are far different now than they were back before the idea of environmental protection took hold.
"Lake Invaders: The Fight for Lake Huron," was written and directed by John Schmit and produced by the Grand Valley State University Documentary Class of 2008. The film shows just how much the opening of Welland Canal, begun in the 1800s to by-pass Niagara Falls and open the Great Lakes to the St. Lawrence Seaway, impacted the ecology of the Great Lakes. The film takes a modern-day look at some environmental consequences that no one even thought of when the canal was first proposed.
The fact is, it took a while for the environmental impacts of the canal to be felt. Fast forward to the 21st century and it's apparent that the Great Lakes - perhaps best demonstrated by Lake Huron - are entirely different ecosystems than they once were.
The negative effects of by-passing Niagara Falls were first noted in the 1930s. By the mid 19th century, commercial fishing had grown to an industry that produced 150 million pounds of fish annually. Then the sea lamprey, a predacious, eel-like fish, arrived. Within a decade or so, the lake trout population in Lake Huron - the third largest freshwater lake in the world -- was virtually non-existent.
As documented by the film, the second alien invader of note, the alewife, had an entirely different effect. In the absence of predators, the population of the forage fish boomed and annual die-offs of alewives made stretches of beaches on the Great Lakes virtually unusable. But some viewed the presence of the fish an opportunity. Dr. Howard Tanner - who was a long-time director of the Michigan Department of Natural Resources - was one of them.
"The alewife problem wasn't really a problem, it was a wonderful food source," Tanner says in the documentary.
In the mid 1960s, Tanner gambled that the "wonderful food source" might support Pacific salmon. He was spot on. By the later 1960s, an outstanding new recreational fishery was created in Lake Michigan with the introduction of Coho salmon. It seemed like a miracle; the baitfish not only supported the Cohos, but the tons of dead alewives washing up on the beaches disappeared. The DNR introduced Chinook salmon to the Great Lakes as well. It seemed the problem was solved.
We now know it wasn't quite that simple.
The film quotes Tanner as saying it was starvation of the alewife population, which had overwhelmed its food source, that caused the die-offs to end so quickly.
"Coho didn't do it," Tanner said. "We might have said that for a minute or two and then said, 'Let's take credit for it.' "
Had the alien-species invasion ended there, the story might have had a happy ending. But the next chapter showed fish weren't the only concern. The arrival of zebra mussels, first found in Lake St, Clair in 1988, changed everything.
The exotic mussels didn't swim into the system, as the alien fish species did, but were what the film describes as an "invisible cargo" in the ballast water in ocean-going freighters, making it apparent that any number of species could find their way in the Great Lakes.
Although zebra mussels caused problems - they feed by filtering the water, impacting the food sources for the bait fish - they were only viable in relatively shallow water. The 1997 arrival of quagga mussels, which are capable of living at depths exceeding 300 feet, seemed to seal the deal. The quaggas removed so much plankton from Lake Huron's waters that the alewife population collapsed. By the early 21st century, adult alewives were virtually nonexistent.
What had been a thriving Chinook salmon fishery in Lake Huron collapsed with the alewives. Although the fishing was outstanding when the alewives began to disappear - the fish were simply hungry - the Chinooks soon outstripped their food source. Adult salmon and other predators began eating the newly stocked fish, leading to year-class failures. It was an economic catastrophe; marinas were empty and bait shops closed their doors. By 2005, the Chinooks had practically disappeared. In a six-year period, participation in the annual Brown Trout Festival in Alpena dropped from more than 1,400 anglers to fewer than 500.
Still, another exotic species figures into the equation. Gobies, which apparently arrived in ballast water as the mussels did, became established in the lakes. But there is at a least a silver lining to that cloud -- lake trout, which were almost forgotten by sport fishermen in their salmon frenzy, are able to utilize gobies as a food source. Lake trout populations have rebounded somewhat.
Walleye, too, responded to the absence of alewives. In this case, alewives were no longer competing with young walleye for food. Now feasting on gobies, walleye populations are nearing record abundance in Saginaw Bay. It's a happy turn of events.
The situation in Lake Huron, however, is far from ideal. As DNRE fisheries biologist Jim Johnson explains, the lake trout were surviving but they weren't growing much. And the survival rate of stocked lake trout had plummeted.
"Young of all species of fish weren't doing as well," Johnson says. "Without the buffer of alewives all the young fish - baby whitefish, baby lake trout, baby perch, young walleye - are being fed upon by the predators that are already out there."
Johnson offers that survival of stocked lake trout is probably now less than half of what it was when the alewife population was viable.
"Lake Invaders" tells this story with footage of everything from anglers enjoying a day on the lake to scientists in laboratories staring into microscopes. It shows men and women of the DNRE and federal agencies struggling to come to grips with the issue.
Lake Invaders has already been shown by several public television stations. The documentary will air April 18 at 5 p.m. on WGVU (Grand Valley State University), April 20 at 9 p.m. on WTVS (Detroit Public Television) and May 11 at 8 p.m. on WCMU (Central Michigan University). In addition, Delta College will host a 6:30 p.m. screening April 21, after which DNRE fisheries biologist Johnson and Fisheries Chief Kelley Smith will take questions from the audience. Schmit may attend, too.
Although "Lake Invaders" doesn't pretend to predict the ultimate impact of alien species in the Great Lakes, it's a crash course on what has happened so far and a wake-up call for what could happen in the future if we don't get a handle on invasive species.
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