Fish Kills at Table Rock Lake, Missouri

August 15, 2015 By Ned Kehde

On Aug 12, Robert Robbins of Branson, Missouri, emailed Stacey King of Reeds Spring, Missouri, several photographs of a fish kill that he crossed paths with while fishing the Long Creek arm of Table Rock Lake, Missouri.

Subsequently, King contacted Shane Bush of Branson, who is the Missouri Department of Conservation's fisheries biologist that manages Table Rock Lake.

On Aug. 14, Bush sent King a report about two fish kills that occurred during the second week of August at Table Rock Lake. King forwarded Bush's report to the Finesse News Network.

Here is Bush's report:

MDC personnel investigated two fish kills on Table Rock Lake today, one in the Long Creek Arm and one in the Kings River Arm. In both places, between 500-1000 fish were observed dead, including crappie, suckers, carpsuckers, bass, walleye, and shad. Suckers were the most common fish observed, but numerous White Crappie were observed in the Long Creek Arm ranging from 3 inches to 12 inches. I took some dissolved oxygen measurements in the area of the kill at Long Creek and there is only oxygenated water down to about 13 feet. From 13 feet to the bottom (around 75 feet) had less than 1 mg/L oxygen concentration. I also took a Ph reading and tested the Ammonia levels in the area of the kill, and neither test showed any level out of the ordinary. The water in the area of the kill at Long Creek was very greenish brown, with clumps of brown algae floating on the surface. As you may have observed, Table Rock turned a greenish color about the middle of last week in response to a large planktonic algae bloom. This is very common when water temperatures warm up following high inflows of water into the reservoir. The water that flows into the lake during flood events is often high in nutrients such as phosphorus and nitrogen, which fuels the growth of algae. This happened in both 2008 and 2011 as well, though we did not observe fish kills during those years probably because the thermocline set up more normal and deeper than this year. I believe the algae died off in the areas of the kills and when it did, it used up the oxygen available to the fish in the area. This occurred in areas that are somewhat blocked from much flow or current, creating more stagnant water conditions and optimal conditions for a large bloom and die off. The water temperature from the surface to the thermocline at 13' was 84 degrees, which is pretty warm. The warmer the water is, the less oxygen it can hold.

Based on the latest DO profile from the USGS, the thermocline is only 20' deep throughout the lake. This means only the upper 20' of water in the lake has enough oxygen to sustain aquatic life. I have also received numerous reports from fishermen saying that they aren't catching many fish. Most people are used to fishing deep in the summer months, but for the remainder of this year there will likely be very few fish located below 20' until the lake turns over this winter. The secondary thermocline starts around 120', but is now low in oxygen and I doubt it is harboring many fish at this point. I suggest telling anglers to fish at 20' or above. In the river arms where it isn't as deep, the thermocline is set up even shallower than that (around 15'). I have spoken to anglers who are still catching fish around 50' deep in the James River Arm. I haven't taken any DO measurements there yet, but it seems that the thermocline either hasn't set up or is setting up deeper than everywhere else. This is likely due to the very high inflow of water in the James, though it remains to be seen whether or not it will set up shallow throughout the rest of the summer and if any fish kills will occur there as well. So far, the James River Arm is the only area we have not documented a fish kill this year.

The good news is that I did not observe any recently dead fish, so events like these may just be isolated and depend on the water quality in certain areas of the lake. It is likely they will continue to occur until the water cools this fall and winter and the lake turns over. With algae blooms, periods of extended cloudy weather can cause the algae to either die or begin using oxygen out of the water. Because it is a photosynthetic plant, it creates oxygen when it forms, but can rapidly use oxygen out of the water as it decomposes or when there isn't enough sunlight to perform photosynthesis. It is likely that we will hear additional reports of fish kills following extended periods of cloudy weather.

Please continue to keep me informed of fish kills as they occur. Unless you observe or hear of something out of the ordinary, you can likely assume that oxygen depletion is the culprit. MDC will work to put out a news release with this information to help educate the public of what is happening. Feel free to contact me if you have any questions.

Thanks,

Shane Bush

Fisheries Management Biologist