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  1. #1
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    Thermocline on down imaging?

    Hey everyone i was out doin some offshore graphing and noticed that no matter where I went on my lake I saw this haze show up around 20’ and deeper I would switch to 2d sonar and it would be clear. I always thought you couldn’t see the thermocline on down imaging but it was consistent on every point ledge and hump I could even see it on side imaging. Can someone help explain. One of the pics has the sensitivity turned up on the 2d in order to see what I thought was the thermocline
    2014 Ranger Z520c special opz edition pushed by a 250 Evinrude E-tec HO and pulled by a 2018 Silverado

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    #2
    looks like the thermocline to me. 2D is showing it as the blue return.

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    #3
    That’s what I was thinking but there’s a 5-6 ft difference between what the di and the 2d shows as the thermocline unless I didn’t have the sensitivity turned up high enough. I thought there wouldn’t be fish below the thermocline and I was seeing quite a few down there below the 20-25’ mark.
    2014 Ranger Z520c special opz edition pushed by a 250 Evinrude E-tec HO and pulled by a 2018 Silverado

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    #4
    What you see here is plankton.
    PS - splitt your screen vertically instead of horisontally and you will double resolution and screen-relastate the way you need it. :)

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    #5
    Plankton? really? That sounds pretty wild but it covers the entire bottom. No matter where I went if it was 17-20ft or deeper it would be there . I remember seeing it last year as well

    That isn’t a normal screen that I use while fishing. I just made it to show the cloud I was seeing on one and not the other.
    2014 Ranger Z520c special opz edition pushed by a 250 Evinrude E-tec HO and pulled by a 2018 Silverado

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    #6
    No doubt what so ever. :)
    Any other stuff that resembles plankton would have covered the full watercoloumn. Plankton go down during the day, and rize slowly up during the evening before it setles close to surface for the night. In the morning it starts to travel down again.

    Another example of the same on 2D:

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    #7
    Wow that’s a nice image you got there I’d love to see that roll across my screen. Is there anyway to hide it or make it less dense so I can see the bottom better? I’ve turned my sensitivity down but I start losing my fish id and small structures. Or do I just need to start rollin around with my 2d and di on the screen? I normally don’t use 2d on any of my screens
    2014 Ranger Z520c special opz edition pushed by a 250 Evinrude E-tec HO and pulled by a 2018 Silverado

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    #8
    Thanks, unfortunately those are all baitfish. :) The screenshots where taken while trolling for northern pike (Esox Lucius).
    No, there is no way to hide plankton (or pollen) without decreasing sensetivity or increasing filtering to a point where you get other problems.

  9. Member tcesni's Avatar
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    #9
    Definitely plankton. Smith Mountain Lake looks exactly like your screen shots this time of year. Down during the day and up at night. Quite amazing really.

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    #10
    Quote Originally Posted by Kickinbass903 View Post
    Plankton? really? That sounds pretty wild but it covers the entire bottom. No matter where I went if it was 17-20ft or deeper it would be there . I remember seeing it last year as well

    That isn’t a normal screen that I use while fishing. I just made it to show the cloud I was seeing on one and not the other.
    im showing the same thing on my units here in NC. I’ve assumed the whole time it was a thermocline. Even the fish and bait were holding on that line mostly.

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    #11
    Quote Originally Posted by Team Colibri View Post
    What you see here is plankton.
    PS - splitt your screen vertically instead of horisontally and you will double resolution and screen-relastate the way you need it. :)
    Plankton .....that surprising. I’ve assumed all along it was a thermocline. I’m getting the same type image as the original poster and a lot of the fish and bait are suspended on that “thermocline/plankton” line.

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    #12
    ^ agreed

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    #13
    When I see that up here in Minn I believe its a thermocline, there won't be any fish below that line here. A easy way to check hook a lively minnow on and let it soak for a good 30 minutes they usually come up dead.

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    #14
    A thermocline looks like a thin stripe:


    There is nothing to doubt about the OPs screenshot, that is plankton.

  15. Member bb45's Avatar
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    #15
    It is for sure a thermocline. I see it here on Lake Chickamauga. It recently flipped due to all the rain and more current flow and fish went dirt shallow. If you turn up sensitivity on your sonar you will see it better, as well, its trying to show up in 25 FOW, on your sonar page. This is quite common in the south when surface temps approaches 90*. I notice plankton in the spring when the water warms into the sixties in the shallows.
    2012 Stratos 294 Evolution, Mercury 200 PRO XS (1B933452).. live 12 / 7 with AT and AI 3N1, Carbon 12 with SS3D, 80lb Ultrex and sonic hub 2.[/LIST]