Erudite number-crunching and computer modeling by Wisconsin Sea Grant researchers will provide information for upcoming state-tribal fishing agreement renegotiations in Lake Superior. At issue is the effectiveness of the Gull Island Shoal lake trout refuge in the Apostle Islands National Lakeshore. Like Marine Protected Areas found across the world, fish refuges are designed to conserve the natural resources within them by limiting human activities. In the case of Gull Island Shoal, the refuge is closed year-round to fishing for lake trout. It was formed in 1976 in response to the near-extinction of lake trout in Lake Superior from the parasitic sea lamprey and fishing pressures in the 1950s.
“This one, very small and fragile population of lake trout was found to be spawning on Gull Island Shoal,” said Principle Investigator Michael Hansen, retired fisheries professor from the University of Wisconsin-Stevens Point. “The refuge played an extraordinarily important role in the recovery of the lake trout population in Wisconsin waters of Lake Superior.”
But since lake trout have rebounded, how important is the refuge in maintaining the lake trout population in the area? That is the question the Wisconsin Department of Natural Resources (DNR) asked Hansen to figure out. After a successful funding proposal to Wisconsin Sea Grant, Hansen enlisted the help of two graduate students – Melissa Johnson and Andrea Koster.
The team took data collected over the years by the DNR and the U.S. Fish and Wildlife Service, analyzing it for historical trends, and matching it to life history characteristics of the lake trout. That data also formed the basis for simulation modeling, which allows researchers to see how the population might respond given different fishing pressures and the presence/absence of the reserve.
The refuge, about the size of 62,900 football fields (including end zones), is found on the far eastern side of the national lakeshore. It encompasses areas around Michigan Island and Gull Island, and extends to the Michigan-Wisconsin border in Lake Superior.
Within the refuge, lake trout spawn on a shoal that is only a fraction of the size – a mere 5,800 football fields. Gull Island Shoal itself is a shallow reef between Michigan and Gull islands, composed of the Apostle Island chain’s characteristic red sandstone. Pebbles, basketball-sized rocks, and piles of boulders form shelves that provide optimal spawning habitat.
Hansen said their results show that “the refuge is hugely important. It is definitely the right design and it’s protecting the lake trout population.” And from previous research, he knows that the trout inside the refuge are healthier. “They suffer lower mortality, they are larger, older and plumper,” he said.
Hansen, who now heads the U.S. Geological Survey’s Hammond Bay Biological Station in Michigan, timed the project so that the results could be used to provide information for the state and tribal renegotiations that reoccur for the area every ten years. According to Jared Myers, DNR fisheries biologist in Bayfield, the process is already gearing up and is scheduled for completion in 2015.
Although it’s clear from Hansen’s research that the refuge is valuable for the lake trout, he is philosophical about the role the information he provides will play in the process. “As a scientist, all I can do is give the information to the negotiators, and they will do with it what they want,” he said. “It’s hard for me to predict what will happen.”
This project was also funded by the Great Lakes Fishery Commission and supported in-kind by the DNR.
