The Department of Natural Resources reported Thursday that two sport fish have tested positive for a fatal viral disease, and for the first time, the disease has been found in Lake Michigan.
The DNR said that a smallmouth bass tested positive for viral hemorrhagic septicemia in Sturgeon Bay and a brown trout also tested positive in Lake Michigan near Algoma in Kewaunee County.
In addition, the state's top fish biologist said that the department has picked up other suspect fish from Lake Michigan and expected more positive results in the big lake.
The finding -- though not unexpected -- is more bad news for Wisconsin's sport fishery, valued by the DNR at $2.3 billion a year.
Thousands of muskies, walleye, lake whitefish and other fish have died since 2005 in Lake Huron, Lake St. Clair, Lake Erie and Lake Ontario, according to the DNR.
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However, the virus poses no threat to humans.
The discovery of the disease in Lake Michigan was expected because the virus had been found in Lake Huron near the Mackinac Bridge this year.
The two water bodies are connected.
The Lake Michigan discoveries come after freshwater drum, or sheepshead, had tested positive on inland waterways this month -- first in Little Lake Butte des Morts and then on Lake Winnebago.
"It's disappointing, but it seemed inevitable," said Mike Staggs, director of fisheries management and habitat protection for the DNR.
"What we are going to learn is that it is pretty solidly in Lake Michigan."
But he cautioned that the agency has found no evidence of a large-scale die-off of sport fish anywhere in the state.
Staggs said that he did not know the precise location of either fish, other than that the brown trout had washed up on a beach near Algoma and the smallmouth was caught in a net by DNR personnel looking for the disease.
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Results of the tests on the brown trout were learned Wednesday night. The test was conducted by the University of Wisconsin Veterinary Diagnostic Laboratory. A backup test has been sent to a federal laboratory in Ames, Iowa.
The brown trout exhibited signs of the disease.
The results of the smallmouth were learned on Thursday. Staggs said the fish appeared to be healthy.
Staggs said that a muskellunge recovered by the DNR from the Fox River also appeared to have contracted the disease. But he said a preliminary test of that fish was negative.
Infected fish transmit the virus through their urine and reproductive fluids. It eventually causes blood vessels to weaken and hemorrhage, according to the DNR.
Some fish can develop antibodies. But over time, antibodies can decline, and the fish can start secreting the virus again and create new cycles of infection.
Even after the virus leaves the fish, scientists have found that it can move through the water and infect other fish for 14 days.
Staggs said the virus has even been known to stay alive in frozen bait.
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The latest discovery will not prompt the DNR to adjust emergency rules approved last week that place restrictions on boaters and anglers in the Lake Winnebago system, because those rules also included restrictions for Lake Michigan, Lake Superior and the Mississippi River and their tributaries up to the first dam where fish could not pass.
The emergency regulations prohibit people from moving live fish, including bait minnows, from one waterway to another.
The rules also require anglers to drain their bait buckets when they are done fishing.
Boaters are required to drain water from their boat, bilge or live well.
-- Copyright © 2007, Milwaukee Journal Sentinel/Distributed by McClatchy-Tribune Information Services.
