JEFFERSON COUNTY — The number of fish disease events or die-offs this year has not been higher than typical in the State of Wisconsin. Despite that, the sight of dead fish floating in the Rock River or bodies like Lake Ripley can still be unsettling to residents.
Warmer temperatures and higher-than-typical rainfall can lead to those events on more local levels. The weather patterns in the Badger State this year — and possibly Jefferson and Dane Counties’ long histories as an agricultural hub — could help play a role in some less-than-exciting wildlife events here.
“Non-Point Source (NPS) pollution is the leading cause of water quality problems in Wisconsin,” said Wisconsin Department of Natural Resources spokesman Zach Wood. “NPS pollution is caused by rainfall or snowmelt moving over and through the ground picking up natural and human–made pollutants, depositing them into rivers, lakes, wetlands and groundwater.
Pollutants include fertilizers, nutrients, oil, grease, sediment and bacteria from agricultural, urban and residential areas.
“Runoff carrying sediment or fertilizers used on croplands can also cause water pollution. Above average rainfall will lead to additional runoff from cropland and livestock operations. Most of the time, this does not cause a sudden drop in water quality that kills wildlife like fish, but it does happen occasionally.”
Going forward, individuals in urban or agricultural areas have little say in the rainfall totals or the temperature. However, following best practices both in large-scale agricultural applications as well as in typical residential gardening or lawn maintenance can help avoid danger to wildlife.
“Better farming practices can reduce this polluted runoff and protect water quality. It’s important to note that urban land practices such as fertilizing and chemically treating weeds in grass lawns also contribute to these issues,” Wood explained. “Wisconsin DNR, DATCP, UW-Extension, Federal Agencies, and County Land Conservation Committees all have roles assisting farmers improve farming practices to protect water quality.
“For fish specifically, we can see sudden, severe drops in die-offs after rain events or after a large die-off of photosynthetic algae/plants. Like mentioned previously, these kinds of events seem to only happen occasionally. Rain events can sometimes lead to great conditions for pathogens (high organic load in water), especially bacteria, that can then overwhelm and lead to outbreaks of disease in fish- especially when they are adjusting to changing water temperatures in spring or if they have some other sort of stressor like spawning occurring.”
Anglers needn’t worry about the fish they catch being safe to eat, though. Whether casting from the shore or from a private watercraft, fish that are healthy enough to pursue bait are typically healthy enough to eat with proper preparation.
Anglers can continue to enjoy fishing and eating their catch,” Wood said. “Fish are safe to eat as long as the fish are fresh, properly handled and cooked. Never eat fish you find dead, decomposing or that appear sick, regardless of cause.”
If citizens do see a body of water with multiple dead fish floating, it is at their discretion whether they are comfortable actually getting into the water themselves for recreation.
“The DNR asks the public to exercise good judgment in deciding to participate in recreational water activities in areas where dead fish have accumulated,” Wood said. “It is reasonable to suggest that the public avoid direct skin contact with dead or dying carp and it is never a good idea to swim or wade among large numbers of dead fish, particularly in stagnant areas of water. As a precaution, people who handle dying or dead fish or swim and wade in the water should wash thoroughly with soap and clean water. Pets should be rinsed thoroughly with fresh water after swimming. These precautions should be followed at all times, not only in the presence of a fish kill situation. Always avoid letting pets eat dead fish.”
Reporting fish die-off events or other adverse wildlife events to the DNR should go through area conservation wardens. A directory can be found by visiting https://apps.dnr.wi.gov/staffdir/contactsearchext.aspx?exp=warden .
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