Where Are Milwaukee’s Fish Hotspots?

Mapping the hotspots for fish in Milwaukee’s rivers revealed surprisingly healthy ecosystems.

For his master’s thesis five years ago, Brennan Dow went fishing.

But his initial project – seeking to determine if yellow perch were spawning in Milwaukee Harbor – would soon grow into a larger search for aquatic life across the city. Dow and his UW-Milwaukee School of Freshwater Sciences professor John Janssen dove deep – literally – into Milwaukee’s harbor and rivers in search of fish, and used bathymetry and sonar to map the underwater landscape. Their two-year fishing trip netted some of Wisconsin’s most prized game species – often in populations healthier than they’d expected given the waterways’ legacy of pollution.

Such information is of interest to far more than fellow researchers and experts in the field, so Dow and Janssen sought to inform the public about their fish findings in an effort to flip the script on Milwaukee’s long-distressed urban waterways. The creatures living, and in many cases thriving, there could be part of the transformation of the city’s waters from industrial casualties to civic assets.

Dow and Janssen teamed up with UWM arts professor Kim Beckmann to create a lushly designed series of maps and accompanying videos that depict and explain the city’s aquatic ecosystems and wildlife.

The maps were released last fall, available online and printed on canvas for Milwaukee Public Schools, while also hanging at Discovery World. The team hopes they’ll also be posted in stores, used as placemats at riverfront restaurants and carried by kayakers.


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The maps and the research behind them are also being used by an alliance of agencies to inform the sprawling project to clean up, rehabilitate and develop the city’s harbor and rivers. Dow, who published his thesis in 2018, now works as the Department of Natural Resources’ coordinator for that effort.

Work guided by the maps would help address one of the “impairments” that led to an “Area of Concern” federal designation: degradation of fish and wildlife populations. Specific recommendations that Dow made in his thesis have become part of the official cleanup plan, including connecting habitat “hot spots” that are shown in the maps – often in man-made detritus like crumbling concrete, twisted metal or jettisoned household items. Creating paths of habitat through the barren spots in between those “islands” could allow, for example, baby fish to safely move between a popular spawning spot in Summerfest Lagoon and a spot near the harbor break wall where they could feast on tiny invasive bloody red shrimp.


View and download the map here

“Obviously a fish living in paradise won’t walk across the desert to get to another paradise,” says Dow. “To connect those spots in order for fish to get from point A to point B was part of the recommendations.”

The maps depict 51 species of fish, including northern pike, lake sturgeon, coho salmon, Chinook salmon, bluegill and rainbow trout. The invasive round goby were also found in abundance, as were swarms of the bloody red shrimp.

Dow obtained his diving certification for the work, and scuba diving in the harbor helped Janssen and him get a fish’s eye view. Janssen described descending through about 10 feet of murky green water near the surface, then dipping into a level of chillier, clearer water, “where you get a shock of cold and suddenly you can see for 30 to 40 feet” below, and “look up at the green ceiling above you.”

He said they knew about the water strata from temperature probes, “but to swim through it gives you a whole different perspective. The salmon that like cold water can be swimming in that cold, clear water but looking for fish in the warm water above, darting up into the warm water then darting down to chill out, like a reverse sauna.”

The Fund for Lake Michigan, which supported the Milwaukee work, has funded the team for similar mapping projects in four more Lake Michigan harbors: Port Washington, Sheboygan, Manitowoc and Two Rivers.

“During the pandemic, one of the things people have realized and found comfort in is the environment,” says Beckmann. “We’re turning our homes into urban jungles because there’s something about nurturing, caring for and seeing things thrive and grow. The maps are a way to help people really understand what’s happening under the water. Some people are absolutely afraid of what’s going on under the water, so if they can truly understand there is a vibrant ecological system there, we can help support and nurture it.”


This story is part of Milwaukee Magazine‘s June issue.

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