Contagious virus destroying fish in Lake St. Clair

Thousands of fish have been dying in Lake St. Clair in what government officials in Michigan are attributing to the largest spread since 2006 of a highly contagious virus.

Known as viral hemorrhagic septicemia virus (VHSv), it does not pose a risk to human health but has been taking its toll this spring on different fish species in the lake — primarily gizzard shad.

Other dead fish found infected in much smaller numbers include bluegill, largemouth bass and muskellunge, said Gary Whelan, research program manager for the Michigan Department of Natural Resources Fisheries Division, which this week issued a public alert.

The virus has been found in the Great Lakes since around 2003 with the last noteworthy area outbreak occurring 11 years ago in the St. Clair-Detroit River corridor, he said.

Early testing of dead fish has shown “very likely VHSv is involved,” Whelan said.

The virus makes the fish’s blood vessels leak. It causes telltale bloody patches, which are a common sign of fish infections, so testing helps confirm whether VHSv is the culprit.

The fear in Michigan is the highly contagious virus will spread more rapidly than in the past to fish other than gizzard shad.

There are also concerns anglers on the water may unknowingly transport the fish virus farther downstream into the Detroit River and Lake Erie.

Anglers are being reminded not to move live fish between water bodies and to properly dispose of bait, Whelan said.

There were several reports of large fish die-offs received this spring, including one from the Canadian side in Lakeshore, he said.

There have been concerns about the potential for VHSv on the Canadian side, but no reports so far this year in the Windsor region, said Jolanta Kowalksi, spokeswoman for Ontario’s Ministry of Natural Resources and Forestry.

“We had reports for Lake Huron and the St. Clair River in late March,” she said. “We collected gizzard shad from Inverhuron Park for testing on March 20. Our preliminary reports showed (the shad) tested negative for VHSv.”

Further testing is still underway, but full results will not be known for a few weeks, Kowalksi said.

“Even with lab tests many times the cause of death we will never know,” she said.

Any resident or angler coming across an unusual fish die-off of 25 or more is being encouraged to call the ministry at 1-800-6671940, she said.

Dave Beyer, of Windsor, was among a group of about a halfdozen who were fishing Thursday in the Detroit River close to the downtown. He was unconcerned about the virus, despite seeing “one or two” dead fish showing bloody virus symptoms recently while fishing in Little River.

“I have not seen nothing like that in the Detroit River,” he said. “But you see these things come and go. I have been fishing down here for 40 years and you take these things for what they are. Something like that seems a little strange, so we will keep an eye out for it. But I’m not too worried about it.”

Any unusual fish die-offs can also be reported to Michigan authorities by email at DNR-FISH-Report-Fish-Kills@michigan.gov, Whelan said. While the virus is highly contagious among certain fish, there are also many species, such as sturgeon and walleye which are essentially immune, he said.

“The virus doesn’t replicate in warm-blooded animals,” he said. “It works at 10 Celsius, but stops at the 15 to 20 Celsius range.

“We are asking the public to keep to keep an eye on this. We have a multi-billion (dollar) sport fishing industry to be concerned about, so we are asking people to report any concerns.”