Researchers at Purdue University are suggesting that fishing by Lake Michigan charter boat anglers has changed in recent years—and the scientists didn’t even have to visit the lake to notice these differences.

In fact, Nicholas Simpson who is the primary author on the study has never even fished Lake Michigan.

Working with Tomas Höök, fisheries ecologist and IISG associate director for research, Simpson, then an undergraduate, compiled 21 years of charter fishing data obtained from the Illinois, Michigan, and Wisconsin Departments of Natural Resources (DNR).

The data, derived from more than 500,000 trips, were readily available from the records charter anglers are required to report to their state DNR after each trip: number of fish harvested—not just caught, location fished, and hours spent fishing.

Simpson, Höök, and their co-authors evaluated patterns for five salmonid species—brown trout, Chinook salmon, coho salmon, lake trout, rainbow trout—harvested from May to September during 1992–2012.

“Because we’re looking at charter fisherman data, there are some biases,” Höök acknowledged. “They’re not randomly going out to catch fish. They go where they believe they’re more likely to catch fish.”

But there is an advantage to examining these data. Researchers often attempt to catch fish in a systematic, unbiased way, and may be limited by factors, such as funding timelines or resources. As a result, “the number of times the lake is fished or the overall number of fish caught wouldn’t be that much,” Höök pointed out. “Here we’re taking advantage of a huge number of people fishing over a long time period.”

The data set covers a time when the lake itself has changed dramatically. Lake temperature and other physical and biological factors are different today than they were in 1992. Over the course of the data set, the distribution and number of prey fish, such as alewives, available for salmon varied greatly.

In addition, while it may be hard to remember a time when zebra and quagga mussels—invasive filter feeders—didn’t line almost every inch of Lake Michigan, zebra mussels were just becoming an issue in the first year of data. Numerous studies have suggested that the mussels have changed the structure of the Lake Michigan food web over time.

The researchers assumed that salmonid species would not be immune to these changes, and some patterns emerged from the charter anglers’ records.

Over time, the amount of time charter anglers spent fishing increased. The anglers also shifted their efforts closer to shore and toward the western and northern parts of Lake Michigan. However, patterns in the harvest of individual salmonid species paint a complicated picture.

Harvest of lake trout and rainbow trout by charter anglers shifted closer to the shore. The same was not true for Chinook and coho, where harvest was consistently farther out in the lake. Brown trout were harvested progressively further west and south, while lake trout were harvested progressively further east. Multiple species were harvested in new locations and at new depths.

In general, the researchers suggest that many of the changes are related to salmonid feeding.

“Previous research has shown the brown trout and rainbow trout and to an extent lake trout are a little more flexible in their diets,” Simpson said. “They were more apt to shift closer to shore and to shallower depths for food. Chinook salmon and coho salmon may not have displayed those trends because they’re more reliant on alewife as prey, which tend to live farther out in the lake.”

“There’s no previous research in the literature that would suggest that coho or Chinook salmon would vary their diet as much as the other three species,” Simpson added.

The researchers stopped short of definitively declaring that fish are changing where they dwell in response to changes in distributions of Lake Michigan nutrients and prey, but they’re confident the results from this paper will be useful.

“The depth and breadth of this data set is what makes it powerful,” said Höök. “While we have to be aware of the biases, fisheries researchers do use catch and harvest data to infer species distributions.”

And while fisheries managers will ultimately need to consider this analysis alongside their own monitoring efforts, Simpson said, “I think it’s useful for fisheries managers especially on Lake Michigan to be able to see that there are shifts occurring.

The study on their findings was recently published in the Journal of Great Lakes Research.

Illinois-Indiana Sea Grant is a part of University of Illinois Extension and Purdue Extension.

Milwaukee residents who have spent most of their lives near the sprawling Lincoln Park have stories to tell about how degraded the park had become. The Milwaukee River was hidden behind buckthorn and other brush and the fish that lived in the tainted water were too contaminated to eat.

Last week they shared some of these memories as part of a joyous celebration that the park and river have been cleaned up. State Representative Mandela Barnes described the park now as “good for people’s health.” At this event, a ceremonial ribbon was cut and the park was officially reborn.

Lincoln Park is in the Milwaukee Estuary Area of Concern, designated by the International Joint Commission. Contamination in the park came from historic industrial and municipal discharges among other sources.

The cleanup of Lincoln Park got its biggest boost from the Great Lakes Legacy Act, which provided federal matching funds from the U.S. Environmental Protection Agency to share the project’s cost with Wisconsin Department of Natural Resources (DNR) and Milwaukee County Parks. Agency representatives, as well as local officials and residents, were on site to celebrate this success story.

Over a four year period, 171,000 cubic yards of sediment laced with an alphabet soup of contaminants—PCBs, PAHs, and NAPLs—were removed from targeted zones in the river and 12.5 acres of shoreline were restored. Commenting the time and work that went into this remediation and restoration, Cameron Davis, EPA senior advisor to the administrator, described the project partners as more persistent than the contaminants themselves.

Throughout the process, Caitie Nigrelli, IISG environmental social scientist was on the ground, keeping the community informed, but also facilitating residents to take some ownership of the park. Nigrelli helped a volunteer organization get started—Friends of Lincoln Park—and joined in the group’s one year anniversary last fall.

Anne Stadler Vaillancourt, a leader of the Friends group, spoke at last week’s event and a number of members were there to set up, take down, and enjoy the festivities. The organization is enjoying success and is ready to grow in membership. They recently held a volunteer cleanup day at the park and more than 100 people showed up. They have two upcoming Weed Out events to remove invasive species on May 14 and May 28.

Stadler Vaillancourt expressed to the morning’s participants that the Friends of Lincoln Park are committed to take care of the park for the long term.

Also in attendance were: Kevin Haley, landscape architect and John Dargle, Jr., director, both of Milwaukee County Parks; State Sen. Lena Taylor; State Rep. David Brown; Theo Lipscomb, chairman of Milwaukee County Board of Supervisors; and Ed Eberle, assistant deputy secretary of Wisconsin DNR.