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MDNR says virus killed thousands of fish in Lake St. Clair

May 1, 2017

Officials have found that a recent outbreak of an invasive virus may be responsible for killing tens of thousands of fish in Lake St. Clair.

The Michigan Department of Natural Resources confirmed this afternoon that the fish tested positive for the viral hemorrhagic septicemia virus (VHSv). The virus first appeared in Lake Michigan in 2006.

Gary Whelan is the research program manager for the DNR’s Fisheries Division. He said in a statement that the results confirm what officials originally suspected.

The MDNR began investigating the deaths of fish in the lake after citizens reported an abnormally high number of fish mortalities.

According to Whelan, "A total of 165 fish have been tested thus far using pooled samples of five fish, and of the 33 pooled samples, 31 of them have been positive for VHSv.” 

More from the MDNR press release:

Based on both public and other DNR and U.S. Fish and Wildlife Service reports, the current known distribution of the fish kill event is from Algonac to Lake Erie, with many of the reports from Harrison Township to St. Clair Shores. Initially, the fish kill was mostly gizzard shad, an important forage species, but now is widening to more species and is likely to affect tens of thousands of fish. This event is considered an unusually large fish kill but is smaller than an earlier VHSv-related fish kill in 2006. The reasons for the fish kill occurring this year are under investigation and the mortalities should begin to be reduced with water temperatures rising above 60 to 65 degrees Fahrenheit.

VHSv affects more than 30 species of fish across the Great Lakes. The virus causes leaks in a fish's blood vessels, leading to visible bloody patches on the skin.

The MDNR is requesting that the public continue reporting kills of more than 25 fish. Boaters can help contain the virus by properly disposing of bait and not moving live fish between water bodies.