Lake Superior Fish May be Building Immunity to VHS Virus

Three years after the fish-killing disease VHS was found in Lake Superior, a researcher will come out with a report next week that says for the first time, fish in that lake may have built up immunity to the disease.

University of Minnesota Extension Aquaculture specialist Nick Phelps says there’s no doubt viral hemorrhagic septicemia exists in Lake Superior. “Now that’s good and bad. It shows us the virus is surviving in fish, persisting in the wild. That’s the bad part. The good part is, it’s not killing them.”

While VHS exists in every Great Lake, and there have been large fish kills in four of those water bodies, there have been no fish kills in Lake Superior. Phelps will report to the American Fisheries Conference in La Crosse next week that VHS may not be the great plague after all: “In some locations, this will no doubt persist and cause long-term mortality events. In other locations, like Lake Superior, it hasn’t had these outbreaks. Maybe it’s water temperature, maybe it’s population density. No, it’s not going to live up to the hype. That’s just a guess right now. Time will tell.”

But Phelps believes Lake Superior fish have become immune. In his doctoral dissertation, which has been four years in the making, Phelps says this immunity may be happening in the other Great Lakes as well, but VHS remains a serious threat. “How long that’ll last for and whether it’s able to be passed from parent to progeny is unknown still, I think. That’s where the time will tell. That’s what we don’t really know.”

Because VHS still has large fish killing potential, Phelps says fisheries need to keep their guard up and keep it from spreading to inland lakes. But he says management practices in fish farms outside the infected areas should be relaxed.