Sudden Fish Kill: Biologist Explains Dead Fish Popping Up At The Lake Last Weekend
LAKE OF THE OZARKS, Mo. — Boaters on the Gravois Arm of the Lake last weekend noticed a surprising number of fish had suddenly gone belly-up, and a local biologist thinks he knows why.
Greg Stoner, Fisheries Management Biologist with the Missouri Department of Conservation, says the sudden fish kill was the result of a viral or bacterial infection that afflicted fish in that part of the Lake. He suspects it was a disease called “columnaris,” which results from Flavobacterium columnare bacteria. He noted the MDC received some reports of the incident scattered in areas around the Lake, but the heaviest concentration of dead fish was in the first couple miles of the Gravois Arm.
But anglers, swimmers and boaters need not be alarmed: the disease is exclusive to fish. It can be fatal for fish, but it can’t be transmitted to humans.
Stoner acknowledged the presence of dead fish can be alarming to people who see it, but the occurrence is not especially uncommon. There was a similar fish kill in 2010, on the lower Gravois Arm. “It’s not unusual in late-spring, early summer when the water temperatures start to climb to have any number of bacterial or viral infections in fish that can cause a fish kill,” Stoner explained.
One boater, Jason Jennings, says he was on the Gravois Arm on Sunday, June 19 when he noticed the dead fish. He said most of them seemed to be fairly small. “You’re used to seeing a dead fish every once in a while, but to see that many was surprising,” he said.
The columnaris bacteria is something even aquarium owners battle, and their first line of defense illustrates why the recent outbreak likely occurred. When columnaris strikes, aquarium owners make sure to drop the temperature of their fish tank below 75 degrees. The columnaris bacteria flourish in warm temperatures, and with the persistent hot weather, the Lake water temperature has risen into the mid-80s.
The disease primarily struck drum in this outbreak, although Stoner said a few catfish and crappie appear to have been affected as well. He also pointed out that fish tend to be physically weaker and more stressed as they come off the spring spawn, and these kinds of diseases have a better chance to take hold, with the fish’s immune system being unable to fight them off.
The MDC does not currently have a fish pathologist on staff, Stoner said, so the department is not able to analyze any of the recently deceased fish in a lab.
“It’s unfortunate,” Stoner said of the fish kill, “but in a body of water the size of the Lake of the Ozarks you’re going to lose a few fish… it just has to run its course.”