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MANITOWOC, WI (WTAQ-WLUK) – The DNR is investigating a fish die-off at Silver Lake in Manitowoc.
After anglers found dead bluegills, minnows, and other fish at the 73-acre lake, the DNR sent crews to investigate.
DNR fisheries biologist Jason Breeggemann spent two days investigating the situation.
The inspection “found very low levels of oxygen at all 12 of the locations that we drilled holes throughout the eastern and western basins of Silver Lake. We also brought an underwater camera along to look for evidence of live fish as well as look for evidence of dead fish. We did observe dead panfish (bluegill and black crappie) on the bottom of the lake along the western and southern shore of the western basin of the lake. Low numbers of dead fish were observed. In each hole that was drilled along the western and southern shores of the west basin, 5 – 10 dead panfish were observed laying on the bottom of the lake,” he said.
The DNR is still trying to determine a cause.
“Water samples were collected at 4 locations, two in the eastern basin and two in the western basin. These water samples were collected to give us a better understanding of what might have caused this fish kill,” he said.
Although one man who fishes the lake said he suspects manure runoff, that has not been confirmed.
“We spoke with several residents and anglers as part of this investigation the last two days and none of them observed any direct discharges to the lake in recent weeks. No one observed overtopping of Silver Creek into the lake during the last warm up earlier in January when much of the snow melted and we got some rain. No one reported smelling any unique smells like sulfur or manure or seeing any unique changes to water quality such as an oily sheen,” Breeggemann said.
Another similar event happened about a decade ago, he said.
“Silver Lake does have a history of winter killing. The last winter kill that was documented by the WDNR occurred during the winter of 2014 – 2015. The fish kill investigation in 2014 – 2015 started the same way as this fish kill when an angler called the WDNR expressing concerns that they were no longer seeing any fish on their electronics while ice fishing and all of their minnows they were using as bait were dead when they pulled them up from fishing. During the investigation in 2014 – 2015, the WDNR observed dead bass and panfish on the bottom with an underwater camera. The WDNR completed a comprehensive fish survey of Silver Lake in the spring of 2015 to gauge the extent of that fish kill and it turned out to be only a partial fish kill. WDNR staff caught over 500 northern pike in their spring 2015 netting survey along with nearly 300 yellow perch, 42 bluegill and 15 black crappie. The cause of the fish kill during the winter of 2014 – 2015 was determined to be internal breakdown of plants and other organic matter along with respiration by fish and other organisms using up the majority of the oxygen in the lake. A spill did not cause the fish kill in 2014 – 2015,” he said.
It will take some time to determine a cause.
“Given the current ice layer, it is very difficult to evaluate the full extent of this fish kill. My team is planning to do a fish survey this spring shortly after ice out to get a better understanding of the extent of this kill,” he said.
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