DNR stops stocking three fish to limit virus spread

TRAVERSE CITY — The Michigan Department of Natural Resources will take a one-year break from raising three species of sport fish and planting them in waterways, hoping to protect the state hatchery system from a deadly virus.

The DNR announced its temporary moratorium Tuesday on production and stocking of walleye, northern pike and muskellunge.

All three are susceptible to viral hemorrhagic septicemia, or VHS, which has caused large fish kills in Lakes Erie, Ontario and St. Clair in recent years. It was detected in northern Lake Huron last fall and was bearing down on Lake Michigan.

VHS doesn’t hurt people but causes fatal internal bleeding for a wide variety of sport and commercial fish.

It’s among many threats to the region’s $4.5-billion fishery posed by invasive species believed to have been released into the Great Lakes in ballast water from oceangoing freighters.

DNR staff has worked hard in recent years to boost walleye numbers in Lake Cadillac and Lake Mitchell.

About 7.5 million walleye fry were planted in spring 2006 but a fall survey failed to detect any survivors from the plant. In fall 2006, the agency planted more than 4,600 walleye fingerlings, ranging in size from 4 to 9 inches.

A spring survey is expected this year to determine the success. The DNR intended to conduct a large spring fingerling plant this year but the plan will likely be scrapped because of the moratorium.

The DNR moratorium won’t prevent the virus from continuing to infest the Great Lakes. But it can help protect inland waters and the state’s network of hatcheries, said Kelley Smith, chief of the DNR’s fisheries division.

“If VHS would inadvertently infect a state fish hatchery, all of the fish at that facility would have to be destroyed and the hatcheries completely disinfected,” Smith said. Losses probably would total $40 million to $60 million, he said.

Muskellunge, northern pike and walleye are among Michigan’s most popular cool-water fish. A federal survey in 2001 identified more than 200,000 anglers in the state who pursue them.

The DNR produces cool-water species at the Thompson State Fish Hatchery near Manistique and the Wolf Lake State Fish Hatchery near Kalamazoo.

Infected eggs at either location could spread to other species there, such as chinook salmon and steelhead trout, said Gary Whelan, the DNR’s fish production manager.

Skipping a year of production and stocking shouldn’t cause a significant population dropoff in any of the species, he said.

“In many water bodies, it will be just a slight bump in the road because we’ve been stocking for a number of years,” Whelan said.

The department considered other options such as isolating walleye, northern pike and muskellunge within the hatcheries or rearing them elsewhere, Smith said. All were rejected as too risky or impractical.

Jason Dinsmore, resource policy specialist with the Michigan United Conservation Clubs, called the moratorium a reasonable step. But a regionwide strategy for dealing with VHS is needed, he said.

“We want to make sure the burden isn’t borne by Michigan alone. We aren’t the only players,” Dinsmore said.

The DNR is writing regulations aimed at slowing the spread of VHS, Whelan said. The U.S. Department of Agriculture’s Animal and Plant Health Inspection Service has limited transport of live fish across state lines in the Great Lakes region and is developing a long-term policy.

Fish kills this spring probably will signal how serious a problem the virus will be, Whelan said. If die-offs happen in the same places as before, it could mean the fish aren’t developing immunity.

“The best-case scenario is that it shows up one time and moves on,” he said. “If there’s continuing mortality, it will be much more difficult to manage around.”