Lake Turnover- Someone enlighten me...

[Crappie Reaper]

I have heard of the lake turning over several times, but am not sure exactly what this means, or does to the fishing. Where is Moose when ya need him?

[labill]

Crappie Reaper.....this may be of help in understanding turnovers.



What Is Lake Turnover?
It happens in spring and fall, and anglers know it affects the location of sport fishes.



--------------------------------------------------------------------------------

Tell someone that the lake you are fishing has recently turned over and most likely that will produce some strange looks and perhaps an image of a lake flipflopping in the dark of night. But turnover is what happens to lake water in the spring and fall. Anglers recognize the effect if not the actual process.

Lake turnover is caused principally by seasonal temperature changes of a lake's surface water. Turnover occurs in the spring when water begins to warm and again in the fall when water cools.

Water circulates and stratifies in a lake throughout the year. Since temperature and circulation regulate the amount of oxygen that water can hold in solution, water temperatures and oxygen levels often dictate where fish are found in a lake. Anglers who adapt their angling to the temperatures and oxygen levels preferred by sport fishes can improve their success.

In winter, water temperatures range from about 39 degrees Fahrenheit at the bottom. Water is densest and heaviest at 39 degrees; colder and warmer waters are lighter. Colder water holds more oxygen in solution. Consequently, oxygen levels usually are high during cool weather, especially in early winter.

The exceptions are shallow lakes or lakes choked with weeds, which can develop oxygen problems during prolonged ice cover. Ice cover does not allow lake water to circulate and pick up oxygen from the atmosphere at the surface. In addition, snow-covered ice prevents sunlight from entering the water, and this slows oxygen production by aquatic plants. Under these conditions, oxygen levels can become depressed due to respiration by aquatic animals and plants, as well as from the decomposition of organic materials such as dead plants. A fish-kill will result if oxygen levels become excessively low.

During winter, most fish tend to seek the warmer water near the bottom.

When surface water reaches 39 degrees in spring, it becomes heavier than the water immediately below it and therefore sinks. The downward movement of surface water forces water in the deeper parts of the lake upward. The resulting circulation of water is called spring turnover. Spring winds also help promote water circulation.

Spring turnover may last several weeks if the weather is cool and windy, or a matter of days if the weather suddenly turns hot and calm. When the water reaches about 50 degrees, it begins to stratify or develop temperature layers.

WINTER
No circulation of water during ice cover. Oxygen levels are usually. high. However, during ice cover, oxygen levels in shallow lakes can become very low. Fish are usually located near the bottom in deep water.



SPRING
Spring turnover - lake water begins to circulate when surface water reaches 39°F. Oxygen levels are high from surface to bottom. Fish are located from shallow to deep water, especially around structures.



SUMMER
Epilimnion - circulating warm water. Oxygen levels are moderate to high. Fish often are confined to the zone which may be up to 20 feet deep.

Thermocline - zone of rapid temperature and oxygen change. Fish will select this zone if oxygen is present.

Hypolimnion - cold, non-circulating water. Oxygen levels are low or oxygen is absent. Fish cannot inhabit this zone for any length of time due to low oxygen levels.



FALL
Fall turnover - lake water begins to circulate when surtaet water reaches about 50°F. Oxygen levels are high from surface to bottom. Fish are located from shallow to deep water, especially around structures.



During spring turnover, oxygen is continually absorbed at the surface as the water circulates. This, plus the fact that the water is cold, results in high oxygen levels. Theoretically, fish can inhabit all areas of the lake, but they tend to lie near the bottom and around submerged structures such as old stream channels, trees and brush. Since most Missouri sport fishes spawn during the spring in relatively shallow water, fishing these waters can be productive.

Water temperature continues to rise through spring into summer, and distinct temperature layers form - a phenomenon called "thermal stratification". Surface water, which is lighter because it's warmer, eventually forms a layer above a zone of colder water. This layer of warm water, called the epilimnion, circulates primarily due to wind at the surface. In deep, clear lakes, this layer may extend 20 feet down.

Since water in the epilimnion continually comes into contact with the surface, it continues to heat up as air temperature rises. This upper layer also tends to have higher oxygen levels due to aeration at the surface and also because oxygen is produced by aquatic plants which live in this zone.

The hypolimnion is the cold, bottom layer of water. In most Missouri lakes, this layer loses most, if not all of its oxygen due to the decomposition of organic materials and the consumption of oxygen by aquatic animals. The density barrier which forms between the cold and warm layers prevents the water in the hypolimnion from circulating to the surface. Little or no sunlight penetrates to the hypolimnion, so oxygen-producing plants cannot survive in this zone. As summer progresses, oxygen levels become depleted, so fish and most other aquatic animals must move to shallower waters which contain adequate oxygen.

Between the warm, upper water and cold, bottom water, a narrow layer called the thermocline or metalimnion forms. Water temperature and oxygen within this layer change dramatically from its upper to its lower levels. During the hot summer months, many sport fishes prefer the cool water in the thermocline, but they may not be able to live in this zone if oxygen levels are low.

When surface water reaches about 50 degrees Fahrenheit in the fall, it becomes as dense as deeper water and sinks. The downward movement of surface water forces deeper water upward. As happens in spring, the water begins to circulate, and this is called fall turnover. Circulation is also enhanced by fall winds. Since the circulating water continually comes into contact with the surface, oxygen levels become high throughout the lake.

The onset of fall turnover sometimes produces a sulfurous or rotten-egg odor. It comes from sulfur dioxide gas produced by decomposition during the summer and trapped within the hypolimnion. When the deep water reaches the surface during fall turnover, the sulfur dioxide is released into the atmosphere.

As in spring, fish can be found throughout the lake. Sport fishes will tend to gather near the bottom and around submerged structures.

Some degree of water circulation can continue until ice covers the lake. When ice forms, wind can no longer provide the driving force to circulate the water. Minor stratification then sets in, with the dense, 39-degree water at the bottom and water as cold as 32 degrees at the surface.

Any lake will have similar turnover and stratification patterns from year to year, assuming weather conditions are near normal. Also, lakes which have similar depths, fertility and exposures to prevailing winds will tend to have similar turnover and stratification patterns. All lakes turn over, but not all of them stratify strongly. Some shallow lakes contain warm water from the surface to the bottom, and even deep lakes do not significantly stratify if they are exposed to strong winds wich can continually circulate the water.

Probably the most accurate way to determine lake turnover and stratification patterns throughout the year is to measure temperature and oxygen profiles from top to bottom. Although electronic temperature and oxygen meters are becoming more popular, their high cost keep them on the wish lists of most anglers. However, if a fishing friend has such equipment, have him/her determine seasonal temperature and oxygen profiles on your favorite lakes. If the lakes you fish have good water quality; water temperature, dissolved oxygen and submerged structures will be the three most important factors affecting the location of sport fishes. Your ability to find good structures in waters which contain preferred temperatures and adequate oxygen will improve your odds of catching fish.

[Crappie Reaper]

Thanks Bill, now I are edjumakated. And, I know alot more about it then I did, that's for sure. Reason why I asked, was that here on Oologah, the crappie never got into the feeding frenzy everywhere else is experiencing. They could be caught all summer long from 8' to 18' of water. I never caught one deeper this last summer. They were also suspended from 4' below surface, to about 16' all summer. NOW, they seem to be at 20-32' depths. I caught a couple yesterday about 12' deep, but most came from the deeper water. A guide mentioned the lake may have already "Turned Over". That's why I asked, thanks again.

[Mo'nBack]

Thanks for the info Labill. I've known about it for years happening in the spring, but didn't know the reasons for it and didn't realize there was one in the fall also. Saline Lake in Winnfield has a drastic turnover a couple of times a year and when it does, no one I know of catches any crappie on it. It turns plumb muddy looking.

[labill]

Thanks for the info Labill. I've known about it for years happening in the spring, but didn't know the reasons for it and didn't realize there was one in the fall also. Saline Lake in Winnfield has a drastic turnover a couple of times a year and when it does, no one I know of catches any crappie on it. It turns plumb muddy looking.

Crappie Reaper....Glad to help, hope it shed some light on the subject.


Mo'n.....our lakes here are pretty much the same when there's a turnover, they are so muddy you can forget about fishing them untill it clears up.
I've enjoyed fishing Saline in the past. Bass, crappie, bream etc....but my favorite is to put a small rubber frog on and toss it in front of some of those big honking bullfrogs, and the fight is on! More fun than a man ought to have, and great eating too!! Try it sometime, it's a blast. Oh, yeah...make sure they're in season to keep the WL&F guys happy....

[Pomoxis 2]

Turnover occurs when the surface water reaches 39.2 deg F exactly as you stated for Springtime. But as I have seen (and read), Fall turnover is the same. When the surface cools to 39.2 it happens.
It is worth noting though, lakes and ponds not deep enough, or located too far south, to develop a true thermocline, will not have a true turnover. They will become slightly stratified in summer/winter and therefore will have somewhat of a turnover when the cooling or warming causes the entire volume of water to reach the same temp (density) and the wind is then able to mix it up, from top to bottom. That would happen at a temp higher than 39.
I have actually done thermocline measurements in a deep lake near me. It is 160 ft deep and located in NJ. Spring and fall turnover DOES occur when the surface (total volume, really) reaches 39.2deg. Fall turnover happens around Dec-Jan. Spring turnover happens around Apr. The thermocline sets up at about 30-40 ft in summer and the hypolimnion contains enough oxygen to support a huge population of Lake Trout all year, every year, just like so many of the lakes in the north. It is oligotrophic (infertile).
There is another lake nearby with 65 feet of water, a true thermocline and the hypolimnion usually gets depleted of oxygen by the end of summer. That lake is mesotrophic (medium fertile).
Hope that helps.

[Pomoxis 2]

I have a thermocline thermometer that I made (patent pending) and may market someday. These days people use those jobs you troll on a downrigger.
I never bought a dissolved oxygen meter, but I don't need one. Here is a cheap and reliable way to see if your hypolimnion (layer beneath the thermocline) is devoid of oxygen:
Put a shiner or herring or shad on your hook and send it down to the depth in question. Use some weight so the minnow can't choose his own depth. Leave it there for a few minutes. Reel it in. If it is dead there is little or no oxygen down there! Hey, you might even catch something during that test.

[labill]

Most of our southern lakes are not consistent in turnovers. It's a hit and miss situation, depending on the temperature. There are times, and not too often, that we have the sudden temp change that makes it happen. It's a wierd thing to watch, if you happen to see it yourself.

Stratification in the south is mostly in the deeper lakes, shallow lakes have a lower incidence of turnover, but in the right circumstances it can happen. Most of our lakes are mesotropic (sp?) in nature, and with all the silt on bottom, a turnover can shut down any fishing for quite a while 'til the muck settles back to bottom. Ain't nature a hoot??

[fishin3]

Most of our southern lakes are not consistent in turnovers. It's a hit and miss situation, depending on the temperature. There are times, and not too often, that we have the sudden temp change that makes it happen. It's a wierd thing to watch, if you happen to see it yourself.

Stratification in the south is mostly in the deeper lakes, shallow lakes have a lower incidence of turnover, but in the right circumstances it can happen. Most of our lakes are mesotropic (sp?) in nature, and with all the silt on bottom, a turnover can shut down any fishing for quite a while 'til the muck settles back to bottom. Ain't nature a hoot??

I know here in Tennessee. Due to the nature of the lakes (damed river sysytem) it is said that we don't have the turn over due to flow thru our system but ever year when the water starts cooling off there is a period people don't catch anything and the water is full of "trash".

[smedley]

We had a severe turnover in our local lake last year. This is the lake that we get our drinking water from and the turnover gave it a very foul taste. Apparently it fouled out some of the pumps at the water works too. I guess a year or so worth of junk on the bottom that suddenly rises to the top will do that.