I know to go to the experts of TFF on this one. I am not sure of what a thermocline is, or if that is even the correct spelling. I am a new boat owner of a 1978 starcraft 16ft boat. I do not yet have a fishfinder, just wondering what it is. Does a thermocline show up on a lower $ fish finder? I know the more you spend on a fish finder the better quality. Are the cheap ones worth the money for a start or should I save up for a better one?

What i know about thermoclines...
When the water heats up from the summer sun, it begins to stratify between the cold deeper water and the warmer upper water. The line where the two waters meet is commonly called a thermocline. Thermoclines should show up on moderately priced depth finders like a Eagle 320 or 480. Some of the lower end DF's are too pixelated to be able show the thermocline. Thermoclines are one of the main reasons that some fish "suspend". Also, toward the end of summer, beginning of fall, when the uppe water starts to cool off, the warmer deeper water will rise above the colder upper water causing a lake to "turn".
Hope this helps. I'm sure others will have better explanations.

"Also, toward the end of summer, beginning of fall, when the uppe water starts to cool off, the warmer deeper water will rise above the colder upper water causing a lake to "turn".
Hope this helps. I'm sure others will have better explanations."


^^^^^^^^^
This probably explains why the fish have been so erratic at the slips this past week and at all different depth, but most noticeable 3-5' in 10-12' of water.

It's been a rough go and think it will remain so until the water re-establishes it's thermal equilibrium.

I'm no expert, but here's what I know about it. Water stratification (when it happens) in a lake, is three part. The hypulum (sp?), thermocline and epulum (sp?). The hypulum is the upper third of the lake. The thermocline is the seperation of the hypulum and epulum and the epulum is th lower third. Depending upon your lake; when the surface temp reaches a certain point, it will start to stratify, causing the 'layers' to form. The hypulum will be extra oxiginated water. The thermocline will be a good mix of ppm of oxygen, and the epulum will be oxygen starved water (it temps will be warmest, optimum and coolest respectivly). Fish will tend to stay in or just above the thermocline during the summer. As the Fall of the year approaches, the water on the surface will start to cool (colder water is heavier than warmer water). As the surface water gets colder (heavier) it will push the thermocline out of existance, and at some point when the surface water reaches a certain temp (weight), the lake will "turn", thereby pushing the bottom water to the surface and vice versa. If fish are caught in the low/non oxiginated water, they have been know to die due to lack of oxygen. The easiest ways to know when a lake turns is to watch the surface water. It will be cloudy and will have an unpleasant smell...and the fishing will tough until the lake stabilizes.

Sorry for being long winded, but this is the "short" version of the process. Hope it helped.

Water Temperatures and Thermoclines

Water temp has an important-if not a controlling- influence upon the activities of all fish. Fish are cold blooded and their body temps are the same of their surrounding waters. During the winter colder water slows down their metabolism. At this time they need about a fourth as much food as they do in the summer time.

Most fish dont spawn unless the water temps is within rather narrow limits. A surface temp meter can help you identify the desired surface water spawning temperatures for various species.
Trout can't survive in stream that get too warm. Bass and other fish eventually die if stocked in a lake that stays too cold in the summer. While some fish have a wider temp tolerance each has a certain range wher it tries to stay. Schooling fish suspended over deeper water lie at a level that provides this temp. We assume they are most comfortable there.

The temp of the water in the lake is seldom constant from top to bottom. Layers of different temp lines form, and the junction of the warm and cool layer lines is called a thermocline. The depth and thickness of the thermocline can vary with the season and the time of day. In deep lakes there may be two or more at different levels. Thermoclines are important to fishermen because they are areas that fish are active, Many times bait fish will be just above the line while the fish suspend below it.



I know this doesnt answer your question on a particular fishfinder will identify the thermocline, but i thought this was a good definition on what a thermocline was.

Good info ya'll!

My question is, does the thermocline say in the middle? If I am on a lake that is 20 ft deeps, will the thermocline be around 10 ft or will it be deeper, since the lake is shallower?

Are there spots on a lake, where a thermocline is non existant?

Thanks to all of you! I now have a good idea of what it is. I just need to get out and do some more research on fish finders. Thanks again

You can find it on all fish finders. The high dollar ones you can see it as a clutter line going across your screen. If you dont see that just go out to some deeper water and drive around and see what depth most of the fish are at and that will get you close to the thermocline. I fish for catfish and have caught them below the thermocline a lot R&R fishing but they will die on jugs below the thermocline. No pro but hope that helps you.

Water only takes about 0.1 degrees Celcius to stratify. Usually when you hear of a thermocline, people are talking about the larger temp shifts in a water column. The thermocline to be most concerned about is the one coinciding with the largest shift in O2 concentration.

The Eagle 320 is a great depth finder at (now) a very reasonable price. You can easily see the thermoclines in a lake with this unit by turning up your sensitivity a little. Also, as mentioned above, drive around and see what depth most of the fish are at. That being said, if you can save and buy something a little more sophisticated, it could pay off in spades IF you take the time to learn to use that extra technology. "IF" is the big word there.

Best of luck. Happy hunting!

Bfail,

Most water sources are stratified at least a little. Very shallow areas with no current(no mixing force)and consistent sunlight would probably give you an area with no thermocline or stratification depending on the circumstances.