Scientists fear deadly fish virus heading toward Lake Michigan
Written by Associated Press   
Tuesday, 10 April 2007 13:34

A virus that has killed tens of thousands of fish in the eastern Great Lakes appears headed for Lake Michigan, where wildlife experts fear it could threaten the sport-fishing industry. Viral hemorrhagic septicemia, or VHS _ which causes anemia and hemorrhaging in infected fish _ was detected earlier this year in fish in an area of northern Lake Huron, about 20 miles from Lake Michigan.

It has been blamed for fish dieoffs last spring in lakes Erie and Ontario, as well as in Lake St. Clair and other waterways.

The virus doesn't pose a health risk to humans, but concern about its potential affect on fish populations is "very high," said Gary Whelan, fish production manager at the Michigan Department of Natural Resources.

"We don't know which species are going to be susceptible," Whelan said. "We don't know whether this disease will come through once and kill off the susceptible and diseased ones," or kill fish every year.

The virus _ which may cause bloody patches on the skin and bleeding in the eyes _ could threaten dozens of species, including many important sport fish such as muskies, freshwater drum and salmon, said Dr. Jill Rolland, a fish pathologist at the U.S. Department of Agriculture's Animal and Plant Health Inspection Service.

That's potentially bad news for the $4 billion-a-year Great Lakes sport-fishing industry.

"It sounds like really, really bad stuff," said charter boat captain Dick Stafford, who for 24 years has been taking people fishing in northern Lake Michigan through his company, Take Five Charters in Gladstone, Mich.

Whelan said the virus, likely a relative of a strain found in the maritime region of Canada, killed several thousand muskies in Lake St. Clair last March and April. In Lake Erie, up to 100,000 freshwater drum might have died last spring, along with thousands of yellow perch, he said. And up to 25,000 round gobies were killed off last May in Lake Ontario.

Whelan said VHS probably made its way to Great Lakes waterways through ships' ballast water, stored in the bottom of vessels to keep them stable.

The virus' spread into Lake Michigan appears inevitable, he said.

"It may even be there now," Whelan said. "It is highly likely we'll see it in the next year or two because there's a substantial amount of movement between those two lakes."

In an effort to help stem the spread of VHS, the U.S. Department of Agriculture last fall banned the transport of live fish susceptible to the virus from Great Lakes states unless they were tested for the virus or complied with other restrictions. The department now is working on an interim rule to address requirements for testing and other issues, Rolland said.

She acknowledged that not much can be done to stop wild fish from swimming where they please _ and the riskiest way to spread the virus is through live fish.

"Without putting up a physical barrier to Lake Michigan, there are some things that we are not going to be able to control," Rolland said.

Even with federal restrictions, some states have decided to act on their own. Last week, the Wisconsin Department of Natural Resources banned the use of imported bait unless it passes testing requirements and outlawed the movement of live fish from the Great Lakes and the Mississippi River.

The Michigan DNR has temporarily stopped the production of walleyes, muskellunge and northern pike in inland state hatcheries because of concern that the virus could eventually jump inland. That agency is developing a long-term policy to address VHS, Whelan said.

Chris Weeks, president of the Michigan Aquaculture Association, said a cohesive strategy is needed to deal with the virus.

"It gets real messy when different states have different regulations coming out of them," Weeks said. "It's very confusing when people want to grow or ship out of state lines."

He said he'd like to see the USDA's interim rule address how to make testing for VHS more affordable. People in the aquaculture industry, who raise aquatic animals for human use, have been the hardest hit by the current order, he said.

"I'm concerned that the financial hardships stemming from the regulatory issues are going to be worse than any hardships that are caused by the disease itself," Weeks said.

Whelan said the full effect of the virus on fish isn't known yet and probably won't be for another year or two. If the virus proves to be a mass killer, it could hurt the fishing industry and create higher costs for managing the lakes, he said.

Scientists hope that the virus becomes manageable or that fish somehow adapt to it, Rolland said.

"The hope is that enough fish survive and reproduce and pass on some kind of immunity," Rolland said.
 
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