Over the past few weeks several dead walleye have been observed at Center Hill Lake. Walleye prefer a cool-water habitat, which means they are usually located fairly deep in the lake this time of year. This year the dissolved oxygen levels in this zone are very low. Data collected yesterday indicated that the only area deeper than about 35 feet that contains any oxygen is a zone between depths of 60-to-90 feet, and even there the levels are quite low.
"This isolated zone of cool, oxygenated water has gotten much smaller over the last few weeks as natural processes in the lake have depleted oxygen from the water. If there are significant numbers of walleye and other fish trapped in this zone they may not be able to survive long enough for the lake to mix and restore oxygen to these lower depths," said Bob Sneed, U.S. Army Corps of Engineers Nashville District Water Management Section chief.
The low oxygen levels are primarily due to a series of rainfall events during the spring and summer that resulted in a loss of oxygenated water from persistent higher flows from the dam. A lower lake pool while maintenance is ongoing at the dam is also a contributing factor.
Cooler nights are helping to restore oxygen levels at lower depths, but Corps officials aren’t sure yet if large numbers of fish could be affected before mixing of oxygen at lower depths can occur.
Sneed said that warmer lake temperatures also translate into warmer water temperatures in the Caney Fork River downstream of Center Hill Dam where a major put, grow, and take trout fishery is managed by the Tennessee Wildlife and Resources Agency.
"The trout are likely to be stressed and they may not feed as aggressively as normal, but I would not expect a major die-off of fish in the river," Sneed said. "We will continue to blend sluice gate releases with hydropower releases to support the downstream environmental resources."
There are no physical or operational actions that can be applied to alleviate this condition. Corps of Engineers and TWRA staff will continue to work together and monitor the situation.