As a young boy, John Janssen remembers his ears perking up in science class when his teacher talked about the lake trout’s disappearance. “The idea that things disappeared in the present,” Janssen recalls, “was really kind of stunning.”
For thousands of years, lake trout were the top predator in Lake Michigan. Then they disappeared. Overfishing, pollution and the introduction of non-native species such as sea lamprey and alewives wiped out the trout. By the mid-1950s, they were little more than a memory. In response, federal and state fish and wildlife management teams began stocking lake trout (and later added brown and rainbow trout), but while this provided action for fishing fans, the lake trout could not create a sustainable population.
Enter professor Janssen, now a senior scientist at UW-Milwaukee’s Great Lakes WATER Institute and heavily involved with efforts to restore the lake trout he discovered as a child. He came here with a background in submersible research – using underwater, remote-controlled vehicles to explore inaccessible areas – as the perfect man to lead an expedition to the offshore reef believed to be a trout spawning ground.
Janssen’s first trip to the Mid-Lake Reef Complex, located 40 miles east of Sheboygan in about 170 feet of water, was in 2001. He returned with the first evidence of lake trout spawning in Lake Michigan in more than 50 years.
Using a small, remote-operated vehicle equipped with a video camera and a suction tube, Janssen’s team collected numerous lake trout eggs and babies. Although they’ve mapped only a fraction of the 2,859-square-kilometer reef, they have already identified two major spawning sites. “Odds are,” Janssen says, “we haven’t found the best site yet.”
Lake trout, he adds, “are very particular about where they lay their eggs.” The rocky reef offers some protection from the invasive species that threaten trout survival and is home to a multitude of tiny shrimp-like creatures that are the young trout’s favorite food.
But others have their eyes on the reef, too. No fewer than three developers have approached state environmental regulators about constructing an offshore wind farm at the Mid-Lake Reef Complex. Developers like the fact that the reef is relatively shallow and hope that an offshore wind farm will face less opposition than land-based development.
But the belief that the reef is a great location “because nothing lives out there,” is a myth, Janssen says. “Fact is, it’s the only place in Lake Michigan where baby lake trout are being produced.”
Ironically, because of his extensive knowledge of the underwater topography of the area, Janssen has also become a go-to guy for energy consultants. “I figure my job is to give the best information possible,” Janssen says. He hopes any future plan for a wind farm includes a trial structure and assessment of its effect on the underwater ecosystem before proceeding to build.
Janssen believes lake trout are an integral part of the Great Lakes and worries about losing the first chance in 50 years for trout to begin reproducing in significant numbers.“Something is going on in the deep water of the Great Lakes that we don’t yet understand,” Janssen says. “If they’re down there, they’re doing something.” And if the trout are scared away or removed from the reef? “You’re likely going to end up with a mess.”
