A brown trout that died in Lake Michigan and washed ashore near the Kewaunee/ Algoma area has preliminarily tested positive for viral hemorrhagic septicemia, or VHS, a new fish disease that was found earlier this month in fish from the Lake Winnebago System.
The trout is the first Lake Michigan fish to test positive for VHS, but fisheries officials have suspected for months that the virus was already in the lake because fish from a connected water, Lake Huron, tested positive for VHS earlier this year. The disease does not pose a threat for humans.
?This is a serious fish disease and we had developed plans to deal with a VHS find in Lake Michigan,? says Mike Staggs, Wisconsin?s fisheries director.
?We had already taken steps in our hatchery and field operations to avoid spreading the disease. In April, we asked the Natural Resources Board to pass emergency rules aimed at preventing anglers and boaters from Lake Michigan from spreading the virus to new waters.?
Now that the virus has been preliminarily confirmed in fish from Lake Michigan, it?s especially critical that all boaters, anglers and others who recreate on that water and its tributaries up to the first barrier to fish take the precautionary steps required by the emergency rules, Staggs says.
People are prohibited from moving live fish, including bait minnows, to another water, and are required to drain all water from their boat, bilge, bait bucket and live well. Anglers should put their catch on ice to take it home and should discard minnows in the trash at the landing. People are prohibited from harvesting live bait from Lake Michigan tributaries over concerns about invasive species.
DNR has long been testing adult trout and salmon from Lake Michigan to assure the fish that eggs are collected from do not have any viruses, and disinfecting eggs after they arrived at hatcheries. When VHS was first discovered in fish in the eastern Great Lakes in 2005, DNR started disinfecting eggs before they were brought into the hatcheries and started testing fish at the hatcheries when they reached ?large fingerling? size, about six to 10 inches long, before they were stocked, to assure they didn?t have VHS.
DNR also is disinfecting boats and gear used in the Great Lakes before they are used in other locations.
?We?ve held ourselves to the highest standards on disease prevention,? Staggs says.
In spring 2007, DNR decided against collecting spotted musky eggs because there is no disinfection process for eggs from such coolwater species — even though tests of adult spotted muskies from the Lake Michigan drainage had all been negative for VHS, dating back to 2005 when testing of those species for VHS started.
On May 17, following the discovery of VHS in fish from the Lake Winnebago system, the state Natural Resources Board extended the emergency rules for boaters and anglers to those waters. DNR took the additional precaution of immediately halting stocking of all fish from DNR hatcheries, transfers of fish among hatcheries, collections of forage fish or eggs from the wild, and all field fish transfers. DNR will maintain those suspensions until it is absolutely sure fish can be stocked safely.
VHS can spread when people move live fish or water carrying the virus to new waters. Infected fish shed the virus into a lake or river through their urine and reproductive fluids. The virus can remain infective up to 14 days and be absorbed by healthy fish. The virus can also spread when a healthy fish eats an infected fish.
VHS is not a threat to people, pets or wildlife but it can infect a broad range of native species and caused fish kills in several eastern Great Lakes in 2005 and 2006. People can still eat the fish they catch, but should take precautions to put their catches on ice at the landing rather than remove live fish from a lake.