DNR says strong wind likely played role in fish kill at North Bay Shore County Park

OCONTO COUNTY, Wis. (WBAY) - The Wisconsin DNR said low oxygen levels exacerbated by strong wind likely led to a fish die-off at North Bay Shore County Park in Oconto County.

Hundreds of dead fish were spotted floating in the water and laying along the shoreline at the park on Friday.

In an email to Action 2 News, the DNR said its Fisheries staff conducted a site visit Friday morning, and D.O. levels were below 3 mg/L at the driveway crossing at what they called “Oconto Park 2,” where the fish kill is reported.

“D.O.” stands for Dissolved Oxygen levels. According to the EPA, D.O. levels measure free oxygen in water, which is essential for aquatic ecosystem health. Ideal levels for fish are usually between 5 to 6 mg/L, while 3 mg/L is stressful and 1 mg/L causes hypoxia.

The DNR said the fish their staff observed included mostly spottail shiners and last year’s year class of yellow perch, which are 3-4 inches long, that were up on the banks several feet up. This suggests that the water levels dropped rapidly in the tributary that flows out of CTH Y and into the Oconto Park 2 marina.

“Yesterday’s strong west wind likely exacerbated the issue with the seiche effect pushing water out. This has occurred a few times due to the same cause in past years, with the most recent being in 2020,” the DNR said in an email to Action 2 News.

The DNR doesn’t expect any significant impacts to the yellow perch population. These events can occur due to environmental related water level changes, particularly during the spawning season, when fish are in shallower waters and waterways.