Yes, the state Natural Resources Board has adopted emergency rules that prohibit anglers, boaters and other recreational users from moving live fish, including bait minnows, and water from the Lake Winnebago watershed, Great Lakes, Mississippi River, and those waters' tributaries up to the first dam impassible by fish. The rules also require that people fishing in those waters use minnows purchased only from Wisconsin licensed dealers, or, if harvesting their own minnows, that the bait is used only on the water it is caught in.
Where is VHS from?
VHS virus is considered an invasive species - not native to the Great Lakes. VHS has been found in the past in fish from the Atlantic Coast of Europe and the Atlantic and Pacific coasts of North America. Historically, VHS was known as a very serious disease of farm raised rainbow trout in Europe. The Great Lakes strain of VHS is genetically different than the strains from Europe and the Pacific Northwest. The Great Lakes strain of the virus seems to affect a wider range of freshwater species over a broader range of water temperatures.
How did VHS get into our lakes?
VHS virus is considered an invasive species (not native to the Great Lakes), but scientists are not sure how the virus arrived. The virus may have come in with migrating fish from the Atlantic Coast. It may have hitch-hiked in ballast water from ships or it may have been brought in with frozen Pacific herring imported for use as bait. Because the VHS virus was confirmed in early 2007 in Chinook and walleye that were sampled in Fall 2006, and lake whitefish collected from Lake Huron in late 2005, fisheries biologists believe the virus is probably already in Lake Michigan, which is connected to Lake Huron. Fish may also already have carried the virus to Lake Superior and ballast discharged from ships may have moved the virus to port cities there. A likely way the disease is spread is through moving live fish or water from one water body to another. The disease has been found in three inland lakes, one each in New York, Michigan and Wisconsin, and could have hitchhiked in a live well, bilge water, on a boat or in minnows or other live fish.
How does VHS spread in a fish population? To new lakes?
Infected fish shed the virus into a lake or river through their urine and reproductive fluids. VHS virus can remain infective up to 14 days in water and the virus particles are absorbed into the gills of healthy fish and infect them. Healthy fish can also be infected when they eat an infected fish.
Infected fish and water can easily spread the virus if they are released into a new water body. So never move live fish, including minnows, from one water body to another and never move water from a water where the virus is suspected or confirmed as present.
Can birds spread the virus?
We don't know yet whether the VHS strain found in the Great Lakes can be spread by birds. But the European strain cannot be transmitted through the feces of birds that eat infected fish - the virus is inactivated in the gastrointestinal track of the birds. The European virus does appear to be able to be transmitted on the feathers or feet of birds that are feeding on a pile of infected fish or sitting in water containing the virus.
What are the symptoms of a fish infected with VHS?
Like many fish diseases, the type of symptoms present in a fish change with the severity of the infection. At low infection intensity, fish may display few to no symptoms. Hatchery or pen-reared fish are much more susceptible to most fish diseases because they are confined. As the infection severity increases, signs include bulging eyes, bloated abdomens, inactive or overactive behavior, bleeding in the eyes, skin, gills and at the base of the fins. Because many of these signs look like those caused by other fish diseases, testing is necessary to determine whether a fish is infected with VHS.
What is the long-term outlook for VHS in the Great Lakes and state fish populations?
It's hard to say because the disease is so new to the Great Lakes. Fish that survive the infection will develop antibodies to the virus. Antibodies will protect the fish against new VHS virus infections for some time. However, the concentration of antibodies in the fish will drop over time and the fish may start shedding virus again. This may create a cycle of fish kills that occurs on a regular basis. However, experiences from other states indicate that fisheries can and have bounced back. We are still going to have a lot of fish in our lakes and rivers for anglers to catch and enjoy.
What should I do if I see a fish kill or diseased fish?
If you catch a fish that exhibits the above-mentioned VHS symptoms, please place the fish in a plastic bag on ice in a cooler and call your local DNR office or DNR's Central Office at 1-800-TIP-WDNR. If you observe a fish kill, please contact your local DNR office or DNR's Central Office at 1-800-TIP-WDNR.