Finding the Thermocline

[airnet]

[QUOTE=Grumpy;495243]Airnet, you are right about ONE WAY to find the thermocline but apparently you didn't really read my first post in this thread. I was trying to help out a fellow that said his fishfinder was old and did not show the thermocline. By going to the COE site for a particular lake, before you go fishing, you can get a good idea where the thermoline is without having to fool with the electronics. You are also right about fish bunching up at and just above the thermocline. The last article I cited says that also:

"In a stratified lake, fish will typically not venture very far below the thermocline, except for brief forays in search of food or other meanderings. They will, however, often hold right at or just above the thermocline. This is why knowing whether or not a lake develops a thermocline and if so, at what depth, is so vitally important to fishing. If an angler is fishing on a stratified lake and putting all their effort at depths below the thermocline, the results will generally not be very pleasing. . . .
Another way to locate the thermocline with electronics is simply by cruising around and paying close attention to the depth at which the fish are marked on the display. If you motor around and see lots of fish congregated at and above 22 feet and see virtually nothing below that depth, it’s reasonable to assume there might be a thermocline at that depth."


Grumpy,,Yes Sir,,,,i did read your first post and was only trying to give some help on how i find the thermocline using electronics,,,some people dont know how to find the thermocline on there graphs,,,so I was only giving my input and trying to help someone out,,,isnt that what we're all here for?,,also,,,I always read your post,,,your a wise man,,thank you for your input,,,,

Airnet

[Grumpy]

airnet, sorry for the mis-interperatation of your post and thank you for the compliment.

A Wised Up Grumpy

[Tom523]

Looking at the charts, for Taylorsville on 7/15, it looks like the thermocline was around 11 - 12 feet. I marked fish deeper than that and even caught a few deeper this past weekend, any thoughts on why they would drop below that level?

I use the thermocline as a starting point. There are many variables to take into consideration such as current, cover, visibility, and barometric pressure. It is possible that fish could be agressive and followed the bait down or it preferred the cooler water over the increase in oxygen. Sometimes in a channel where the current is flowing faster, the water has increased oxygen in the current even though it is below the thermocline. I just found that the thermocline is a good place to start.

[Moveon]

You will find that when you get that sudden change in water temperature in just a foot or two that the amount of Dissolved Oxygen will also drop right below the thermocline. The lake water is STRATIFIED and it's this stratification that forms the boundary between the hot water and the colder water and this is where you will find the OXICLINE as well.


The epilimnion is where you will find the most fish. Below the thermocline you have the hypolimnion and that's where the water is devoid of dissolved oxygen during the hot summer months when the lake is stratified by temperature.

An easier way to find the thermocline is to just watch the depth finder and not the depth where most of the fish are located in the hot summer months. Fish will suspend above the thermocline and you can determine the thermocline by just watching to see where the fish suspend.

Also remember that different species of fish have different dissolved oxygen requirements. Rough fish like catfish or carp may not need as much dissolved oxygen as a Small Mouth Bass.

If you have 5 ppm of Dissolved Oxygen most fish can survive and lay eggs in this type of environment.

Cold water holds more dissolved gases so therefore colder water will hold more dissolved oxygen. But in the summer months when the lake is stratified the cold bottom water can be devoid of dissolved oxygen. The reason is that the bacteria in the lake bottom consume all the dissolved oxygen as they feed on the dead algae that falls down though the water column. And since the lake is not mixing oxygen from the surface to the lake bottom the lake bottom becomes devoid of dissolved oxygen. So that's why you won't find many fish down in that colder deeper water. And there is not enough sunlight reaching the deeper bottom areas so there is not plants growing. Remember that green plants produce oxygen when they undergo photosynthesis. Fish can be found in the shallow waters where there is a lot of green plants growing as the plants give them oxygen and shade from the sun.

I've been out on my lake trolling crank baits at depths up to 10 to 12 ft and catching a lot of Largemouth Bass. The thermocline on these lakes runs around 25 ft during this time of the year.

I use a YSI dissolved Oxygen meter and temperature probe to find the thermocline. This is the same equipment that the COE guys use to develop the DO and Temp data for the COE web sites.

Tom, you are absolutely right. I didn't want to get into that in my original post but I also check the change in temperatures to get the probable location of the thermocline. HOWEVER, over the years I have been doing this, I have found that it is much easier to see the drop in oxygen content then the drop in temperature. Both ways are correct and will help to eliminate a lot of unproductive water by not fishing deeper than thermocline/depleted oxygen depths. As Peter said, "To know where fish will not be is huge."

Grumpy

[uk.bass]

So at what depths do bass stay at in relation to dissolved oxy level?Do you fish the depths that have 2 to 4% oxy? So what depths do you fish during fall when that oxy level is the same at different depths?

[Grumpy]

UK.BASS, Before I go fishing I check the COE site for the lake I am going to fish. I find what depth has at least 2 parts dissolved Oxygen, then on the lake I don't fish any deeper than that depth. If you look at any of the charts, the oxygen content will usually increase the closer you get to the surface; therefore I think there is enough oxygen to hold bass from the thermocline to the surface. Also, I will usually motor around an area and watch my fish finder to see if I can find a depth where they fish seem to be staying at OR ABOVE, and then fish from that depth to the surface.

From everything I have read and experienced, the thermocline (and the dissolved oxygen line) will be at about the same depth EVERYPLACE in the lake. So, lets say its at 15 feet, I don't worry about it when i get into the shallow parts of the lake, e.g. less then 30 feet dpeth, because there isn't enough depth for stratification to set up and I may fish anyplace for the surface to the bottom. Conversely, if I am sitting in 40 feet of water I do not bother fishing on the bottom or anyplace deeper then I found the thermocline to be.


Now to the second part of your question, after the fall turnover, there won't be any thermocline and the dissolved oxyben content will be almost uniform from top to bottom AND THE FISH MAY BE ANYPLACE FROM TOP TO BOTTOM. In my example early in this thread, I said that the reading for Rough last October showed 5.1 dissolved oxgen at the surface and 4.3 at 50 feet, so there is plenty of oxygen for the fish at any depth and you just have to find them the old way: look for them.

Hope this helps,

Grumpy

[uk.bass]

UK.BASS, Before I go fishing I check the COE site for the lake I am going to fish. I find what depth has at least 2 parts dissolved Oxygen, then on the lake I don't fish any deeper than that depth. If you look at any of the charts, the oxygen content will usually increase the closer you get to the surface; therefore I think there is enough oxygen to hold bass from the thermocline to the surface. Also, I will usually motor around an area and watch my fish finder to see if I can find a depth where they fish seem to be staying at OR ABOVE, and then fish from that depth to the surface.

From everything I have read and experienced, the thermocline (and the dissolved oxygen line) will be at about the same depth EVERYPLACE in the lake. So, lets say its at 15 feet, I don't worry about it when i get into the shallow parts of the lake, e.g. less then 30 feet dpeth, because there isn't enough depth for stratification to set up and I may fish anyplace for the surface to the bottom. Conversely, if I am sitting in 40 feet of water I do not bother fishing on the bottom or anyplace deeper then I found the thermocline to be.


Now to the second part of your question, after the fall turnover, there won't be any thermocline and the dissolved oxyben content will be almost uniform from top to bottom AND THE FISH MAY BE ANYPLACE FROM TOP TO BOTTOM. In my example early in this thread, I said that the reading for Rough last October showed 5.1 dissolved oxgen at the surface and 4.3 at 50 feet, so there is plenty of oxygen for the fish at any depth and you just have to find them the old way: look for them.

Hope this helps,

Grumpy

Well, whats the optimal water temp for bass?

[Grumpy]

uk.bass: do a Google search for "bass water temperature preference" or similar leadins and you can get a lot of good material to check out. For that matter, Google is a great starting point for any infromation you want to find on any subject. Try it, you can get a lot more information then I could give you.

Grumpy

[nmvfd795]

For someone trying to learn different strategies in bass fishing this has been a helpful thread.Thanks!! to all involved.

[Moveon]

Cold blooded animals take on the body temperature of their environment. But remember that fish need or consume more food during the hot summer months that the cold winter months.

I think that the amount of sunlight filtering down through the water may have more to do with how deep the fish go than the water temperature. Fortunately their is a direct connection between water temperature and the amount of sunlight penetrating the water column. This makes is hard to seperate these two variables and determine which one impacts the fish the most.

Well, whats the optimal water temp for bass?