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Kansas Fisheries Staff Allay Fears With 25-lake Study on Largemouth Bass Virus

For Immediate Release: March 31, 2022

Contact: Nadia Reimer CMP®, Chief of Public Affairs (785) 338-3036 nadia.reimer@ks.gov 

EMPORIA – Though it’s been 15 years since Largemouth Bass Virus (LMBV) was first identified in a Kansas lake, Kansas Department of Wildlife and Parks (KDWP) Fisheries Division staff remain committed to fully understanding the effects of this disease on one of Kansas’ most popular sportfish.

Beginning in 2018, Fisheries staff from KDWP’s Research and Survey Office in Emporia systematically examined 25 waterbodies across Kansas that had presumably healthy, popular largemouth bass fisheries; populations with declining relative abundance or size structure; and, populations that were previously identified as being positive for LMBV. While the study brought to light the presence of LMBV at eight waterbodies not previously known to harbor the virus, what may be most surprising is the data that wasn’t there.

Largemouth Bass Virus Study Highlights

  • A total of 1,260 largemouth bass were examined throughout the three-year study.
  • Of the 25 waterbodies tested, 14 of those waterbodies tested positive for LMBV, six of which were already known to have LMBV.
  • There was no evidence of LMBV effects on body condition, relative abundance of quality-length fish, or growth rates. 

Staff were surprised, but relieved, to learn that there was no evidence of LMBV having long-term effects on body condition, relative abundance of quality-length fish, or growth rates in the Kansas populations.

“It’s very possible that the acute effects of LMBV have already occurred in some of these impoundments,” said Jeff Koch, KDWP Fisheries research supervisor. “If that’s the case, that likely means many of these populations have already rebounded and have perhaps even developed some degree of immunity to the virus. In fact, some of our best largemouth bass fisheries tested positive for LMBV and have not shown evidence of any substantial population-level effects. Either way you look at it, the data is promising.”

Symptoms of LMBV typically occur in waterbodies during the heat of summer or other periods when fish are stressed. Though not all infected fish exhibit outward symptoms, LMBV can cause buoyancy and swim bladder issues, causing infected fish to lose equilibrium and become lethargic, ultimately resulting in death. Currently, LMBV has been found in the eastern and southern United States, though more research is still needed to understand the full extent of its range. 

“Largemouth bass virus is a relatively new disease, so it’s all the more important that we continue to study its range and effects, and add to the scientific community’s body of knowledge,” added Vanessa Salazar, KDWP Fisheries biologist. “Thanks to the hard work and expertise of many biologists in our division, we’ve been able to accomplish just that.” 

Similar to most aquatic pathogens, LMBV is transmitted in water or even damp livewells.  Anglers are encouraged to clean, drain, and dry their boats and equipment before moving to a new waterbody to help prevent the spread of aquatic pathogens and nuisance species.   

To learn more about KDWP’s study, visit https://afspubs.onlinelibrary.wiley.com/doi/10.1002/aah.10133 to access the March 2022 issue of Journal of Aquatic Animal Health’s, “The Effect of Largemouth Bass Virus on Bass Populations in Kansas Impoundments.”

To learn more about largemouth bass in Kansas, visit https://ksoutdoors.com/Fishing/Fish-Species/LARGEMOUTH-BASS.

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