Lake Superior’s newest troublesome invasion won’t come from a giant Asian carp after all, but from a tiny virus that already has caused massive fish die-offs along the eastern Great Lakes.
Researchers at Cornell University announced Wednesday that they have found fish-killing VHS virus in fish samples from Lake Superior, including the Twin Ports harbor.
Fish from Superior Bay and St. Louis Bay, as well as some from Paradise and Skanee Bays in Michigan, tested positive. Some of the results have been corroborated by other laboratories; others have tests still under way.
Viral hemorrhagic septicemia is harmless to people but often lethal to fish. VHS can cause bleeding in fish tissue, including internal organs. Sick fish often appear listless, have bulging eyes, swim in circles or hang just below the surface.
The disease can spread in infected water or infected fish. Once a fish is infected with VHS, there is no known cure. Not all infected fish develop the disease, but even fish with no symptoms can carry and spread the disease to other fish. Fish have no natural defenses to VHS but may be able to build-up immunities
VHS was previously believed to be a cold-water, mostly saltwater disease killing species like salmon in European streams. But it has spread to the U.S. and, for the first time, is killing cool- and warm-water species.
VHS was first found in the eastern Great Lakes in 2005. As of 2009 it had been confirmed as far west as Lake Michigan, Lake Huron and Lake Winnebago in Wisconsin. It has been found in more than 40 species and killed fish from more than a dozen species. In Lake Huron, VHS was found in whitefish, walleye, and Chinook salmon. Farther east, it has killed musky, perch, drum, emerald shiners, in some cases by the thousands.
The long-term effects of VHS on fish populations, commercial and recreational fishing and tourism remain unknown. It’s also not known how well the disease will thrive in cold and infertile Lake Superior. But it may take better hold in slightly warmer-water estuaries like the lower St. Louis River and Twin Ports harbor.
Supporters of stronger regulations to thwart invasive species say VHS is only the latest of 180 species to invade the lakes.
“This is what happens when you don’t have proper regulatory protections in place,’’ said Henry VanOffelen, natural resource scientist for the Minnesota Center for Environmental Advocacy. “What’s going to come next? Are we going to keep delaying action until something else comes down the lakes?’’
Local experts say they aren’t surprised by the finding because the Great Lakes are connected by water and ship traffic. Since it can’t be eradicated, efforts will turn to limiting VHS’ spread to inland waters – especially convincing anglers and boaters to take precautions.
“It’s very unfortunate but not unforeseen... It’s obviously going to change how anglers and management agencies conduct business,’’ said Brian Borkholder, fisheries biologist with the Fond du Lac Band of Lake Superior Chippewa. “I would hope the gravity of the situation will change the way anglers and recreational boaters move their boats around and clean their boats and take seriously the threat of getting VHS into the inland waters of Minnesota.’’
Dennis Pratt, Wisconsin Department of Natural Resources fisheries biologist in Superior, said VHS so far hasn’t caused major problems here.
It’s not clear how long the disease has been in local waters, although tests in 2008 and earlier found no infected fish.
“The interesting thing is that we haven’t seen any mortalities [fish die-offs] yet,” Pratt said. “Mortalities are usually caused by a combination of things: a virus along with fish being stressed, such as during a warm period, or high-water events or spawning periods.”
“The important thing, locally, is to tell the DNR if you do see a major number of dead fish — and be vigilant in trying to contain it,’’ Pratt added.
The virus variation found in the Great Lakes had never been seen before. It flourishes when water is between 32 and 59 degrees Fahrenheit, generally when many fish are spawning and are most vulnerable to disease.
Minnesota and Wisconsin agencies have moved to restrict transportation of live bait across state lines to help slow VHS. Agencies, mostly the DNR, also are changing how they move fish for stocking programs, especially around Lake Superior, to prevent moving potentially contaminated fish into other waters.
“We’ve changed a number of our management practices to prevent against any inland transfer if it were in the system,’’ said Don Schreiner, Lake Superior area fisheries supervisor for the Minnesota Department of Natural Resources.
Both Minnesota and Wisconsin also are moving to require that Great Lakes’ ship’s ballast water be treated before being released to kill invasive species in ballast tanks. It’s believed many foreign species in the Great lakes, including VHS, may have moved around by hitchhiking in ballast water.
Ship operators already have agreed to avoid taking in ballast from waters infested with VHS, and saltwater ships are supposed to flush their ballast tanks at sea. But it appears those efforts, and new regulations still years from taking full effect, are too late to stop VHS from spreading.
Dave Zentner, Duluth angler and natural resource activist, said he’s angry that more wasn’t done sooner to stop VHS and other species from moving into Lake Superior. Zentner and several local organizations were part of an effort that tried but failed to force federal agencies to act against VHS by regulating ballast water. Their lawsuit was dismissed in federal court.
“This (discovery) illustrates the utter failure of the state and federal regulatory and legal systems, especially federal, to protect our natural resources,’’ Zentner said. “Now all we can do is try to keep it from spreading.’’
Subject: VHS found in Lake Superior 
Thu Jan 28, 2010 11:37 am
