The MDC is more concerned with a second fish kill affecting large, mature paddlefish near Warsaw. The first report the department received was on May 5, 2017 and began as soon as Truman Dam started releasing a high flow out of their spill gates.

Various factors are currently causing two separate fish kills in Lake of the Ozarks, according to a Missouri Department of Conservation resource scientist. 

Rebecca O'Hearn, a water pollution biologist who coordinates the fish kill and water population program for the department, said several species are being affected by a naturally occurring virus or disease as well as turbine causing deaths from swimming through the Truman Dam. 

The first fish kill, estimated to be from the 38-mile marker to the 55-mile marker, is affecting channel and blue cat fish, walleye, crappie, and drum. A pathologist with MDC is scheduled to collect samples in the Lake of the Ozarks on Wednesday, June 21, 2017 to determine the specific bacteria, virus, fungus or disease causing high mortality rates. 

"These fish are showing signs of disease, naturally occurring disease, most likely related to rising warm temperatures this year. It was particularly hot last week, lower levels of the lake are going to become depleted in oxygen," O'Hearn said in an interview Tuesday afternoon. "There's very little habitat available to swim and live in, and that causes stress." 

On top of those factors, O'Hearn explained that it's also spawning season for these species who have a particularly brutal way of mating that involves rapid swimming and bumping into each other to release the sperm and egg. MDC received several reports last year at this same time of the summer, but near the Gravois Arm where a large fish kill was believed to be caused by a bacteria. 

"It's a pretty rough process for them which lowers their immune response and makes them susceptible to these naturally occurring disease agents," O'Hearn said. "We don't know what point in the bell curve we're in, we thought we had maybe peaked last weekend, but that doesn't seem to be the case." 

The scientist explained that a typical fish kill of this nature can last a couple of weeks with a life cycle resembling a bell curve. The first reports contain a few fish, then an increase, followed by a maximum level, before declining, and the event eventually concludes. 

"There's really not a lot of risk to people swimming in the water," O'Hearn noted. "It's going to be fine and rebound." 

The MDC is more concerned with a second fish kill affecting large, mature paddlefish near Warsaw. The first report the department received was on May 5, 2017 and began as soon as Truman Dam started releasing a high flow out of their spill gates. 

"These paddlefish are swimming in front of the turbine section, entering the spill section and getting hit with blunt force trauma from the flow, a drastic change in flow," O'Hearn explained. "There's no way for them to know, they're blindly swimming into it. We're seeing a lot of spinal cord fractures. Simply, they're being decapitated by these high flows." 

The paddlefish cannot spawn in reservoir environments that use dams, and any paddlefish that is killed has to be replaced by raising the species in MDC hatcheries and restocking the Lake, which can be a costly and timely process. 

"This is not just a one time thing this year, we saw it last year around this time with the high flow and paddlefish, you can look at back to the 1970s," O'Hearn said. "We're also seeing background levels of fish mortality from turbine passage and borrow trauma, the bends in fish, from moving from the high pressure of Truman to the low pressure system of Lake of the Ozarks on the other side of the dam." 

O'Hearn said the Army Corp of Engineers has attempted to try a few different things to mitigate mortality and injuries of fish, including building a structure that lessens the severity of the flow as well as slowly releasing water through the spill gates to oxygenate the water below the dam, but it doesn't appear to be helping the paddlefish who are being shredded by the mechanics of the dam.