Fishing the thermocline

Discussion in 'Flathead Catfish' started by chad69dart, Jul 29, 2009.

  1. chad69dart

    chad69dart New Member

    Messages:
    93
    State:
    Alabama
    Hey Guys.

    I know there are some smarter guys on here that maybe can help me understand fishing the thermocline.

    I understand that the thermocline is the area where the water separates from moderately tempetutered highly oxygenated water and the lower colder less oxygenated waters. i also understand that fish will suspend in or about the thermocline and feed at or around those depths.

    My problem is that most info on thermoclines is based on lakes and i fish mostly in rivers. Does the faster constantly moving water of the rivers effect the thermocline? If so whats the best way to ID the thermocline. Are you still looking for suspended fish? Im thinking of moving into some the more still waters of the backwoods lakes to give it a try to fish the thermocline.

    Im fairly sure that Im dealing with it regardless as if i bottom fish a large gill in deep water before long he is dead as a door nail. I am associating this with depleted oxygen levels below the thermocline.

    Thinking that im going to start suspending some baits at the levels where I can determine the thermocline and see if my strikes pick up as opposed to fishing the bottom all of the time.

    Any smart guys got any input? Sure would like to have a better understanding of this.

    thanks Chad
     
    Last edited: Jul 29, 2009
  2. jim

    jim New Member

    Messages:
    2,579
    State:
    Jacksonville NC
    Tricky subject!!Rivers do have TCs but due to the currents etc it is much harder to define them.You already have good evidence with the dead gills.Lift the baits up until they stay alive and you will have better success for sure.Even in lakes its hard to get a good picture sometimes of exactly what depth the TC is because wind and wave action will tilt it.At Santee I have found the it sets up between 18-24 ft most of the time.NOT all the time but on average during the hot summer months.As we drift over humps in that depth range with bait associated with them the bite is much better.Not to say fish wont drop below into the lesser oxygenated water for a quick feeding opportunity.A good fish finder will usually see a set up TC if the sensitivity is adjusted correctly.:big_smile:
     

  3. lforet2002

    lforet2002 Well-Known Member

    Messages:
    1,534
    State:
    Tennessee
    Never heard of a river stratifying..If you have some info on rivers stratifying could you give us a link..
     
  4. kitsinni

    kitsinni New Member

    Messages:
    1,573
    State:
    Ohio
    Is there an average depth that the thermocline will be at or is different everywhere? My fish finder isn't good enough to actually show fish :eek:oooh: so I would have a hard time locating it.
     
  5. jim

    jim New Member

    Messages:
    2,579
    State:
    Jacksonville NC
    Best link would be to search on here or go into the library.Next best would be In-Fishermen website.All water stratifies just like all water will freeze.TCs in rivers are much harder to define because of the functions I previously defined.Position on a river would also be critical,for instance a deep slow moving pool would be more likely to have a TC than a shallow riffle.Normally I wouldnt worry in a river with reasonable current.However on the James which has 90ft+ depths a dead zone can set up quickly.SImplest test of all is send that poor gill or perch down on a reseacrh project.Give him 15min and haul him up.If he (she) is dead and the eyes are protruding then that water is lacking oxygen obviously.Move him up until they are surviving or are eaten.:smile2::big_smile:
     
  6. chad69dart

    chad69dart New Member

    Messages:
    93
    State:
    Alabama
    no real average as I understand. It tends to move up and down dependent upon the ambient temp and conditions. Most stuff i have read seems to point to anywhere from 10 to 20 ft.

    I haven't found any links to define if a moving river system will have a definite TC or not but the evidence of my dieing bait is pointing in that direction. Im not smart enough on this subject to know how active current will effect the thermodynamics of the river. It still makes since that somewhere along the vertical line there would be an optimum temp and oxygen level even if the river is moving.

    I guess I will do as Jim suggested and move my bait up and down until it stays alive .Im hoping this will increase my bite and pick up some bigger fish. I know my fish finder is showing most fish staged at 5 to 10 ft but Im not sure I trust it as its not that accurate.


    Thanks guys.
     
    Last edited: Jul 29, 2009
  7. RonSki

    RonSki New Member

    Messages:
    380
    State:
    Indiana
    This is simply not true. Sorry Jim, but I'll need to see an actual scientific study. All water is different. Some lakes do not stratify, most rivers do not. In order for stratification to occur, there needs to be drastically warmer and cooler layers of water. This is not a problem in lakes as there is no current to mix the water and layers can't form. In some shallow, windswept lakes a thermocline never forms due to the wind induced current mixing the lake. This is well documented. In rivers, there is current which mixes the layers and distributes oxygen evenly. Rivers CAN stratify when there is very deep water, high temperatures, and very little current. I could see it happening in water 90 feet deep if there's little current, but just because your baitfish dies does not mean there is a thermocline present and is at best a guess.
    To REALLY determine if there is a thermocline present you will need a temperature gauge at least 20 feet long. When there is a thermocline present, you will notice a RAPID decrease in water temperature at some point. For example, I measure the thermocline on a lake where I musky fish last year. The surface temp was 82 degrees. At 16 feet it was still 80 deg. But from 18 to 20 feet, it dropped 4 degrees to 76. From 20 to 22 feet, it dropped another 3 degrees, and continued dropping slowly deeper than that. So the thermocline in my lake started at 18 feet. This was later verified by an Indiana Fisheries biologist, who also took oxygen readings. I can't remember the actual numbers for the oxygen readings, but it was very low.
    There's only one way to find out if a thermocline is present, but there are many more reasons why the baitfish died. I don't mean this post to sound negative Jim, but there is no research on stratification in rivers because it rarely happens. I'd love to see what you can find, I couldn't find ANYTHING stating that rivers stratify...
     
  8. chad69dart

    chad69dart New Member

    Messages:
    93
    State:
    Alabama
    OK Then why are all the fish staging so high up. I did find many articles on stratification on lakes but little or none on rivers. I can buy that the current would keep things mixed up but Im trying to ID the reasoning for most of the fish staging in 15FT or less of water. The average dept in most of the rivers is 25 to 30 Ft with some deep holes in the 40 and 50 ft range.

    I dont see me investing in high dollar test equipment it doesnt me that much but if anyone has any good hypothesis on this I sure would be interested in hearing it.

    I guess the only way for a poor redneck to test is to put out 5 or 6 rods at varying depths and see what the hell happens.
     
  9. RonSki

    RonSki New Member

    Messages:
    380
    State:
    Indiana
    Chad, there could be a billion reasons why the fish are up high, none of which we'll really be able to figure out without being there. Usually it's either food, cover or comfort. But there's really no way to tell. I would take a wild guess that it's probably food or cover related, but really, what does it matter why? I would focus on finding out where they are, not why they're not where they aren't.:wink:
    As far as the thermocline thing, you don't need high dollar test equipment. Just a temp gauge with a long cord. Minn Kota makes one for $11 http://www.reedssports.com/Product/product.taf?_function=detail&_ID=8871
    Not a super accurate gauge, but when I compared what I got from what the biologist got with his high dollar equipment, it was so close as to not matter.
     
  10. jim

    jim New Member

    Messages:
    2,579
    State:
    Jacksonville NC
    Ron I didnt mean to imply that all bodies of water stratify and a TC forms,completly not true as you said.I did say all water stratifies in that different layers of temp form to a degree.The only time this doesnt happen to a large extent is in bodies of water the freeze but even then the top layer is the coldest and the bottom warmer.I also didnt say the dead fish is an indication of a TC only of a layer of water low in oxygen Sorry if I caused any confusion.:big_smile: My advice is forget about the TC and find structure that has bait on it and you will find fish.
     
  11. katfish ken

    katfish ken New Member

    Messages:
    4,092
    State:
    Paintsvill
    Lakes will have a TC,but it is hard to say at what depth without being on the lake. There are a lot of things that factor in to the TC. Water running in from tributaries,wind and rain all play a big part in the TC. There are sonars that will show a Thermacline IF you have them set properly.
     
  12. JimmyJonny

    JimmyJonny Well-Known Member

    Messages:
    4,059
    State:
    sc
    Ah, I'm glad to see this thread up. I've been debating this among myself for some time now and have concluded...the heck with the Tc.

    Yes, you can drop a bream down in the Tc and it dies, the worst of the bunch are herring...takes practice keeping them going. Most deaths are due to the temp difference between the bait tank and the water temp/depth....and don't forget ammonia build-up and it goes on and on during the summer.

    My observations are that cats, bass, bream, gills, gar, carp, threadfins, crappie, white perch, yellow perch all go up into the so called " not enough O2 level waters". And to top it off it's fully loaded up with turtles, gar, and Blue Herring ( the bird ) whom all feed on all the above.

    I bank fish, and pretty much 3 times a week, usually 12 hour shots each trip. I only fish shallow, and all year round. I have a lot of time to sit back and closely observe what's going on in great detail....well, its because I'm basically sitting in one spot I guess, LOL. My area covers well over a mile and I know it well, very well. I can assure you these fish aren't just zipping in to feed and then zipping back out. There is way to many baitfish towards the main body ( up to 180' ) for them to feed on. Now the Striper and Blue back herring do need the correct depth but that's because of their sensitiveness. Even with them I see the smaller 1# and 2# Stripers and hybrids smashing threadfins a few miles back in 5' of water.

    All I know is I catch cats all the time in theses so called dead zones and lots of folks reports show shallow catches too. Two night ago I got 4 fish in the back of the run. The depth in there was only 3' to 5' and loaded with gills and threadfin's.

    Now with all do respect ,I aint arguing anyone's theories but I wanted to see what everyone else thinks too, and if you all have had similar experiences like me.

    -Jim-
     
  13. jim

    jim New Member

    Messages:
    2,579
    State:
    Jacksonville NC
    Totally agre Jim.The TC is way overrated as to fishing effect.I have seen it clear as day on the fishfinder and when I get that depth tied to structure and bait I catch fish.My adice would be forget about it.As you astutely pointed out virtually all fish can venture into the low O2 levels for a meal.Be the same as holding your breath while you grab a steak off the table at the Outback..:big_smile:To many variables as it is to worry about withoutthis one.:smile2:
     
  14. Rtpcat

    Rtpcat New Member

    Messages:
    72
    State:
    Alabama
    I don't know how to fish it but, the alabama river will get dead spots in it. Fish will stage in the upper 10-15ft(avg depth 30) and when you get to a good hole 45-55 ft hole there is a big temp change. I think the moving water just moves over the colder deep water, normally there is a fairly sharp drop going into the deeper water. I can't catch anything in the hole in the summer but I can in the spring. When the surface temp is 91-93 like it was a few weeks back somewhere between the top and bottom has to be the most comfortable spot. But I just want to know what depth they feed in. That I am still hunting for.
     
  15. RonSki

    RonSki New Member

    Messages:
    380
    State:
    Indiana
    If I'm not confused again :wink: I just wanted to clarify that the oxygen deprived layer is below the thermocline, not above. Everything else is right on.
    In a river, I don't worry it, but in a lake, it could be a big deal. I do know when I'm muskie fishing, once the water warms to about 75 degrees, almost ALL of them go down and relate to the top of the thermocline. They don't do well in hot water so they go deeper to be more comfortable. Flatheads like warm water so I'm almost never fishing deeper than 12 feet deep. But I think that's also a trait of the river I'm fishing too as there isn't a lot of very deep water to start with.
    Targeting fish around the thermocline comes down to knowing the nature of the fish you're after. Muskies, don't like the warmer water, so they go deeper but are limited as to how deep they can go by the thermocline. Flatheads like warm water, so there's no reason for them to need to go deeper other than food. As far as flatheads go, I wouldn't worry about the thermocline, but it IS something to keep in mind if you're fishing in a lake or very slow flowing reservoir.
    I'm still extremely curious about these "dead spots". Some rivers COULD have a thermocline, but the conditions for one to form must be perfect. The only way to know for sure is to check the water temps at different depths. I would LOVE to see what is really going on down there if anyone with a known dead spot would check it...:wink:
     
    Last edited: Jul 30, 2009
  16. Mr. Foster

    Mr. Foster New Member

    Messages:
    1,352
    State:
    Kansas
    This thread has to do with bluegills dyeing. Im not trying to insult anyones intelligence, I find this very informative. But could the gills be dyeing of other obvious reasons, like hook placement? Ive seen people put the hook directly in to vital organs and or the spine. Maybe they are on there death bed in the bait tank/bucket? Sometimes we overlook the obvious. This is jus a oppinion or thought. Thanks to everyone explaining the thermocline and its importance, its good stuff to know. I will be trying a new stratagy due to this.