New virus leads to carp kill on Lake Francis

May 27, 2020

ELYSIAN — A new carp-killing virus has made its way to Lake Frances.

Carp edema virus has been monitored by the Department of Natural Resources since 2017, and CEV appears to be the root of the lake’s common carp kill during the past several weeks.

CEV also has been the cause of several other carp kills in Minnesota over the last several years, and there have already been three cases of it in the state this year.

“Carp can carry it in the population, but it takes certain environmental conditions to trigger it and cause a kill,” said Craig Soupir of the DNR.

Isaiah Tolo, a graduate assistant at the University of Minnesota, studies CEV. He said the trigger generally comes in the spring, as that’s when the carp spawn. Once the stressor is added, the carp become more susceptible, and CEV is spread. To make matters worse, carp tend to congregate when they spawn, which leads to easier transmission.

It’s important to note the virus doesn’t seem to affect other fish populations, just carp. But that doesn’t mean it will always be like that.

“Viruses do have a tendency to mutate in nature. We hope that doesn’t happen, and at this time, it hasn’t,” Soupir said. “There’s always that chance it could mutate and affect another species.”

When it comes to the long-term impact on the ecosystem, it’s too early to tell, but it likely won’t be a negative. Common carp are bottom feeders, which means they eat plants critical to a lake’s health. Soupir said those plants are generally replaced by algae, which makes lakes murky and green. The destruction of those plants is also hard on the native fish populations from a habitat standpoint.

There’s no way to know how many carp the virus will kill or how much this will impact the carp population in Lake Frances in the years to come.

“Carp are very destructive to our lakes. We have a lot of projects where we try to limit carp or reduce carp numbers,” Soupir said.

Dead carp have been washing up on shore and that’s likely to continue. However, for residents familiar with the 2017 Lake Elysian carp kill, there won’t be as many because Lake Frances has a much smaller carp population.

There are a number of different things that can be done with the dead fish, as they can be thrown away or composted. It’s also fine to just let nature take its course. The natural deterioration does no harm to the lake, the Soupir said.

“It’s one of our more developed lakes, so people are going to have to deal with it,” he said of the dead fish. “If left in the lake, the nutrients held in the fish will go back to the lake. Other organisms will use those nutrients.”

As far as eating fish from Lake Frances, Tolo said there’s no evidence the virus can be transmitted to any other species besides carp, including humans. But he also warned it’s not necessarily good to be eating fish from a lake during an active fish kill.

“There’s a lot of bacteria and algae that get nourished by those carp rotting in the water,” Tolo said. “I would say just use some caution when it comes to eating fish during a mass mortality event of carp.”