• As whitefish disappear from most of the lower Great Lakes, southern Green Bay is a remarkable exception
  • Once almost nonexistent in the bay, whitefish have boomed since first returning in the late 1990s
  • The reasons why aren’t clear — but finding answers could aid whitefish recovery efforts throughout the Great Lakes

It’s one of the lower Great Lakes’ last whitefish strongholds, in one of the unlikeliest locations:

Southern Green Bay — a water body once so polluted the fish that managed to survive often weren’t safe to eat, where nutrient-laden runoff still leaves the water murky, anoxic, and algae-choked in summer.

Bridge Michigan published a story today on the mysterious whitefish renaissance in Green Bay — and the consternation over early signs of decline.

Scientists remain hopeful that recent recruitment issues in the bay’s whitefish population won’t spiral into the kind of all-out collapse that is plaguing whitefish elsewhere in lakes Michigan and Huron. But some have begun to wonder whether it’s time to start tamping down on harvests.

Photos from the bay’s world-class ice fishing scene help tell the story of its whitefish resurgence and ongoing efforts to protect the species — a mission that could provide clues for Michigan and the rest of the Great Lakes.

Ice shanties on a frozen bay
Ice-fishing shanties dot Green Bay. (Daniel Kramer for Bridge Michigan)

Once almost nonexistent in lower Green Bay, whitefish have boomed since first returning to the area in the late 1990s. A world-class ice fishing scene has sprouted up in kind, with anglers flocking by the thousands each winter in hopes of catching their 10-fish limit.

Men clean fish
The Lindal Fisheries crew clean fish recently near Green Bay. (Daniel Kramer for Bridge Michigan)

The bay’s whitefish revival has been a salvation for Wisconsin’s commercial fishers, giving them somewhere to turn when whitefish began to struggle in Lake Michigan’s main basin. While their harvests in Lake Michigan have plummeted from 1.6 million pounds in 2000 to less than 200,000 pounds in 2024, harvests in Green Bay have surged from less than 100,000 pounds to more than 800,000 pounds.

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When the Lindal Fisheries crew isn’t processing their own commercial catch, they keep busy through the winter cleaning, fileting and vacuum-sealing fish caught by recreational anglers. 

A man points to a computer screen
Scott Hansen, senior fisheries biologist with the Wisconsin Department of Natural Resources, points to data on a screen showing the whitefish population in Green Bay. (Daniel Kramer for Bridge Michigan)

After years of remarkable productivity, the bay’s whitefish population has begun to show signs of decline. Scott Hansen, senior fisheries biologist with the Wisconsin Department of Natural Resources, keeps track of the changes using sophisticated models fed data from state fish surveys and commercial and recreational harvests.

While adult fish in the bay seem to be thriving, fewer baby fish have made it to adulthood in recent years. It’s not clear why.

A man holds up a small calcium deposit taken from a fish
An otolith, also known as an “ear bone,” is pulled from a whitefish near Green Bay. (Daniel Kramer for Bridge Michigan)

Like rings on a tree trunk, scientists can tell a fish’s age by counting rings on their otoliths. Also known as ear stones, the small, bone-like structures float in the heads of most fish species, accumulating layers of calcium carbonate with each passing year.

State scientists collect otoliths from fish caught by commercial and recreational anglers, using the data to understand how fish populations are changing.

A man holds up a vial
Dan Isermann, a fish biologist with the US Geological Survey, displays a transmitter that will be implanted in a whitefish. (Daniel Kramer for Bridge Michigan)

With whitefish still so new to southern Green Bay, there’s still much scientists don’t know about them — how they got there, why they suddenly rebounded or what’s causing the recent declines.

Hoping to get a better picture of the population, scientists like Dan Isermann, a fish biologist with the US Geological Survey, have been catching fish, implanting transmitters onto their bodies and then releasing them back into the water. 

Listening stations positioned throughout the bay will pick up tracker signals from nearby fish, helping scientists understand how the fish move throughout the waterway.

“What we want to know is, what spawning areas are important to the fishery?” Isermann said. 

That knowledge could help scientists protect important spawning areas in hopes of boosting the species’ reproductive success.

Michigan’s collapsing whitefish

Bridge Michigan senior environment reporter Kelly House spent months examining the near-collapse of whitefish in the lower Great Lakes. Here are the stories we’ve tackled so far:

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