New Virus Identified in Wisconsin Bass

As concerns about Largemouth Bass Virus (LMBV) mostly have been put to rest, researchers in Wisconsin have identified yet another virus that seems specific to the species.

“This could be inconsequential to largemouth bass or it could be an existential threat to the species,” said Tony Goldberg, an epidemiologist at University of Wisconsin-Madison. “At this point, it’s all new and we are trying to find out more.”

Largemouth Bass Reovirus was isolated at the U.S. Fish and Wildlife La Crosse Fish Health Center from dead fish collected during an investigation of a May 2015 kill at Pine Lake in northeastern Wisconsin. Its genome was sequenced at a “virus hunting laboratory” operated by Goldberg. He and his associates searched through genetic databases to see if they could find anything similar.

They could not, although it is related to  viruses associated with other fish species.

“Largemouth Bass Reovirus is only the second representative of its group of viruses,” Goldberg said. “These viruses are emerging pathogens that infect all sorts of animals. They cause kills in marine and freshwater fisheries, including wild and farmed populations.”

But he emphasized that this virus has yet to be linked to fish mortality. More investigation is needed before it can be determined if it caused the bass kill at Pine Lake, where no large fish kills involving bass or any other single species had been previously recorded.

Meanwhile, the Wisconsin Department of Natural Resources isn’t advising management changes in response to the discovery. “We would hope people will continue with their due diligence and follow the rules in place that seeks to prevent spread of viruses and other fish health concerns,” said David Giehtbrock, fish culture section chief.

B.A.S.S. National Conservation Director Gene Gilliland added that he hopes this announcement will not cause over-reaction, as was the case with LMBV and associated kills a decade ago.

 “It (LMBV) caused a huge outcry among anglers wanting state agencies to do something (close lakes, prohibit tournaments, etc.), but it was collectively decided that there was little anyone could do,” he said.

“No real transmission mode was ever identified, no real preventatives, no cure. It had to run its course and the affected populations built immunities and recovered.”

Biologists still find bass carrying LMBV from time to time in fisheries around the country, but die-offs associated with them have been few and minor for several years.

Gilliland added that he’s also concerned that some anglers “will blame the ‘new bass virus’ as the culprit rather than admit they are the possible cause (for dead bass) by continuing to do stupid things like having 8- and 10-hour-long tournaments in the hottest part of the summer,  and expecting all of the catch to survive.”

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