"Turning over"

[Jigg-N-It]

Can you guys tell me exactly what it means when a lake turns over? Do they all do this. All I know is it gets real mossy. but why? less light? cooler lake temps.
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[fishnate]

Water is most dense at 39 degrees so as the surface water cools it decends to the bottom causing the now warmer lower layer to rise, thus the term "turnover". With that turnover sediment, moss, etc often rises with the warmer water. It happens twice a year usually on deeper waters, not sure what the magic depth is but lakes over 40 feet usually have turnover. Shallower lakes are constantly mixed by wind. It'll mess up the fishing for about a week.
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[PapaBaruu]

Here's a lengthy explanation - but worth a read..

[black][size 1]Turn over is an expression used to describe the way a lake changes in temperature after the long hold of winter has loosened its grip. Basically what happens is that the water nearest the surface is colder during winter than the water below. As the surface warms it eventually becomes the same temperature of the deeper water. When this happens the water of the lake mixes together and creates turn over.

This creates turmoil for the trout, in that oxygen that was once concentrated in the “thermo cline” is now dispensed through out the entire lake. The thermo cline is the zone of water where warm and cold meet. This is where most of the oxygen is concentrated in the lake.

Over the winter oxygen cannot be replaced. This is due to the fact that most lakes are covered in ice and therefore have no wave action to create oxygen. Also aquatic vegetation is either dead or in a dormant state. Therefore most trout need seek out the thermo clines particular towards the end of winter. If the winter is a particularly hard and long, the oxygen can be completely used up. This causes “winter kill.”

Spring kill is caused when the turn over takes longer than normal. No wind and/or a sudden cold snap can be deadly to the fish. Since there is no concentration of oxygen the fish cannot all find enough to survive, a partial spring kill is imminent.

Turn over usually happens in the first two weeks after ice off. The period pre turn over will find most of the oxygen in shallow water. Therefore most of the fish will be in the shallows searching for food. Concentrate your efforts in the shallows at this time using chironomids, shrimp and water boatmen. This can be some of the fastest fishing of the year and should relished by the fly tosser.

One can recognize a turn over usually by the amount of bottom material floating on the surface. Since there is no thermo cline most of the water tension will dissipate causing neutral buoyancy products to come to the surface. At this time it would be recommended to go to a different lake. Try changing elevation, as most lakes in the same elevation will turn at the same time. Also larger lakes usually turn first.

Post turn over will find the fish concentrated in deeper water. This can be a frustrating time to fish, as the trout are harder to reach and find. This is when a depth finder can be crucial to success. [/size][/black]

[black][size 1]As the season progresses oxygen will spread out through the entire lake. The fish will fall into normal feeding patterns.[/size][/black]
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[black][size 1]A similar turn over occurs in the fall as the large moss beds developed throughout the summer on the lake bottom begin to break apart as thermal currents become stronger and more active. This causes the moss particales to release and float throughout the water columns - large areas of clouding then occur until the moss can resettle. [/size][/black]
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[black]All I know is sometomes it's easier to catch fish than others...PB[/black]
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[kokeking]

very good post papabaruu,i knew what it was but the sure explanied it alot better then i ever could have. i know it sure can cause havoc on the gorge when it turn's.
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