Educate Me On Thermocline

I understand some about the how and why. I've been targeting night crappie in deeper locations and believe I see the thermocline when fishing in these deeper places as I try to keep in the vicinity of the creek channels. I ventured into less deep water recently and didn't see the line indicating a definite thermocline but the water was deeper here than where the thermocline appeared on my HB when over deeper water. Will the thermocline set up over the whole lake (smaller body of water) the same? I would think cooler water streaming in a shallower area might be different. On another note, many of the fish I handle have an obvious warmer feel to them but sometimes I'll boat one that is noticeably cooler to the touch. Did he just join the frenzy from a cooler, deeper level?

I am no expert but if I understand correctly a thermocline is less likely to set up in moving water like your creek mouth.

Yes ... thermoclines can & will set up at different levels in different parts of the lake. Many times when I quote the thermocline level from the COE Lake Level website, I get responses that other's observations of the levels are different. I, then, have to quantify the fact that most COE thermocline levels are taken at the dam of that lake, where the water is deeper and more stable than many other areas of the lake.

It is quite possible that the "cooler feeling" fish did, in fact, come from deeper water ... but, depending on how close to the thermocline you were fishing, they may not have come from a "much deeper" depth (they could have been simply at the lower portion of the thermocline, where the water temps are cooler, but the O2 content was still at a sufficient level).

I duck hunt with 2 P-3 orion drivers and all they did is hunt subs.

There stories about thermocline and sonar is unreal.



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Thermoclines cannot set up if the water is moving. (This is why rivers & streams do not set up that way.) Most reservoirs, unless they are really large, cannot set one up either, due to moving water. If you do take a fish and it's noticeably colder than some of the others you've caught, it may be from an underground spring near bottom structure that is attractive to the fish.

If you've ever did any swimming in a river, you know that some areas and depths are colder than others. Springs.

The most recent spot chosen to set up for night fishing did indeed have a slight...very slight current there due to a creek channel I suppose. Consider me more educated on thermoclines. I actually have been avoiding the thermocline and keeping my offerings well above but it appears I may have been limiting myself. I might need to dip a little lower and maybe even in the line. I was under the apparently wrong impression that there was zero oxygen available there but now it seems I should focus a bit deeper with a couple rods in these hotter months. I will report back. Never too late for old dogs to learn new stuff. I thought I knew everything cause my wife always tells me I'm a know-it-all anyway.

Good information :ThumbsUp

if there is a definite thermocline in a water body you will notice NO fish below the line in most cases . most graphs indicate it as a horizontal line with clutter below it and no fish .
it can vary from spot to spot on a lake and like the posted before if the lake has current or "bubblers" / aerators as we call them there wont be one to the best of my knowledge .
one thing for certain if it sets up good in a deeper lake the fish get REALLY easy to find and ketch because they have less spots to visit ....

There are different thermoclines, and you have to know and understand what is going on also!
You can have temperature thermoclines in Summer or Winter, and they are ended by "turnovers"....fish can be at any level still.
Then you also have thermoclines that are oxygenated in one layer and "dead" in the other...Normally in late summer the bottom of the Thermocline is void of oxygen (Dead), and in the Winter (Northern Areas) the top layer is void of Oxygen!
Normally if you have sufficient Summer Storms, a thermocline will not set up...it takes a lot of stagnant weather and heat!

Crappie are considered a cool water fish, they prefer temps in the low 70's and will seek out cooler or higher oxygenated water in the summer.
At 80 degrees+ they can no longer consume enough calories to offset their metabolism...they will suspend during the heat of the day, and hunt at night when their night vision gives them an easier advantage.
And Yes, IN THE DAYTIME, if you provide them with an easy meal right in front of them, especially if they do not have to work for it, they will eat it...they are opportunistic! :)

Maybe this will help:Reservoir Stratification, Thermoclines, and Turnover - Lakecaster Online - 9/04

Never seen a thermocline here on Ky Lake in my locale. Mainly because of depth which is average 12 foot. You can watch the rise and fall of plankton on the sonar starting about dusk and ending before dawn though. You can also see plankton migration. Some folks think that the plankton migration is the thermocline. I have seen miles and miles of migrating plankton.

Water changes levels here constantly, so not much time to set a thermocline.

You can smell the turnover of the lake sometimes. Smells like rotten eggs.

All the eggbeaters running up and down the lake keep the water churning which aerates the water and spreads the nutrients.

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Originally Posted by Cane Pole

Never seen a thermocline here on Ky Lake in my locale. Mainly because of depth which is average 12 foot. You can watch the rise and fall of plankton on the sonar starting about dusk and ending before dawn though. You can also see plankton migration. Some folks think that the plankton migration is the thermocline. I have seen miles and miles of migrating plankton.

Water changes levels here constantly, so not much time to set a thermocline.

You can smell the turnover of the lake sometimes. Smells like rotten eggs.

All the eggbeaters running up and down the lake keep the water churning which aerates the water and spreads the nutrients.

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Dang, I had no idea KY Lake was that shallow...I always thought it was like Cumberland??
Interesting.

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Originally Posted by INTIMIDATOR

Dang, I had no idea KY Lake was that shallow...I always thought it was like Cumberland??
Interesting.

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Not even close, Intimidator .... KY Lake is a lowland reservoir & Lake Cumberland is a highland reservoir. Average depth of KY Lake is 15ft, while the average depth of Lake Cumberland is 90ft. Surface acreage at Summer Pool : Cumberland @ ~50,000 acres & KY Lake @ ~160,000 acres.

"You can watch the rise and fall of plankton on the sonar starting about dusk and ending before dawn though". I have seen this on my sonar in the lake I fish also.
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Originally Posted by scrat

"You can watch the rise and fall of plankton on the sonar starting about dusk and ending before dawn though". I have seen this on my sonar in the lake I fish also.
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You won't see that at our lake because it is so full of plankton and algae...our lake is deep and fertile, plankton and algae thrive ....it's also the reason we are able to sustain such a huge shad and fish population in a 2500 acre lake.
Having a fertile reservoir in the middle of farm country has benefits but also drawbacks. Once Blue/Green algae is established, it is a terrible battle to fight in the summer!
Even though our water is heavily stained, you can see distinct Thermocline features...sometimes the thermoclines will be in certain areas on day and move around a week later.
when we do get a Bad Thermocline, because of all the oxygen use by all the fish and microscopic critters, it sets up at 13 feet in the entire lake and NOTHING will be below 13 feet....this BAD Thermocline will last until the Fall Rains.

Great and useful info. And thanks for the screenshots.

Plankton on the rise right after sundown on the left screen.. You can see the fish on the stakes. Billbob pulled in a 2 pounder here.

http://i188.photobucket.com/albums/z...208/shot10.png

Sometimes the plankton form a thin like belt a foot or two off the bottom. I don't know why. This is what some folks believe to be a thermocline when it is actually zooplankton.

When fishing late evenings around my place, you can see fish of all makes and models sometimes breaking surface and scooping up the zooplankton. They just swim around with their mouths open and get a belly full. When the fishes start breaking water near our dock, I pitch the a minner 1-2 ft below a bobber. I also burn the water with small roadrunners. Sometimes I git lucky.

Crappie Stalker and I have been out on Big Sandy mid day when plankton was so thick it looked like the boat was running on ground (0 ft on sonar depth) when we were actually in 20-25 ft water.

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Originally Posted by scrat

"You can watch the rise and fall of plankton on the sonar starting about dusk and ending before dawn though". I have seen this on my sonar in the lake I fish also.
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Can you explain what I am looking at in this pic? It all looks like a big mess to me. That is my main problem , I can't cipher what I am looking at on the finder.

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Originally Posted by Nutbush

Can you explain what I am looking at in this pic? It all looks like a big mess to me. That is my main problem , I can't cipher what I am looking at on the finder.

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You're actually looking at two pics. The thick yellow line is the bottom and the reddish/purple stuff above the bottom is what they feel is plankton. I have no experience with plankton that thick, so I don't know.