The result was that slowly but surely, as the summer got hotter and drier, the water temperatures began to creep up. Not enough cold water was coming through the gates from the lake to maintain the colder downstream water needed. Soon trout in the lower portion of the river were scrambling to find water cold enough to survive.

"We found that all the trout downstream were going to the mouths of tributaries, where the water coming in from the feeder streams was a little bit cooler, until they practically stopped running," said Dreves.

"We were fearful that we might lose some or all of our fishery in the lower portion of the river just because the water temperatures were borderline too hot. But fortunately that didn't happen."

Dreves said that a decent rain, coming at just the right time, allowed the Corps to release water.

That was enough to pull the temperatures back down and remove the threat in the main stem of the river. He also noted, however, that the prolonged period of high temperatures caused most of the trout to move into the upper portion of the river, which had remained cooler despite the minimal flow out of the dam.

"We found some evidence of trout that were pretty stressed and hadn't been feeding normally, in spots where fish had always proven chunky and healthy in past studies," he said. "We collected some fish that looked pretty thin in the gills, along with trout that were fat and sassy.

"We didn't see a die-off anywhere. But it appeared that some of the fish living where the hotter water was were continually moving upstream to find the temperature they needed to survive, and the stress affected their feeding levels and growth.

"Fish that lived in the upper part of the river looked great. In fact, we found some of the highest densities of both rainbows and browns -- and higher quality trout than we'd recorded in several years. I expect the stressed fish will bounce back," he added. "But we had a pretty good scare for a long while. I hope it's a normal rainfall year this summer so we don't run that risk again."

Interestingly, Dreves says that the Cumberland River isn't really all that productive in terms of food sources for young trout. It does have some particular types of aquatic "bugs" --caddis flies and stoneflies, for example -- for small fish to feed on and grow.

Dreves believes that the Cumberland River receives less fishing pressure than other high-quality trout waters in the region.