Thermocline

Discussion in 'Catfishing Library' started by Whistler, Sep 1, 2005.

  1. Whistler

    Whistler Well-Known Member

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    State:
    TN
    Original post made by Jackie Johnson(Abilene) on August 20, 2004

    The larger blues do prefer open water and they do suspend and they do so in groups. Thermocline is the reason and this also applies to the minnows, baitfish and all other fish.
    The very largest blues suspend also but more usually they will do so on under water ledges and drop-offs or cover or structure, whichever you prefer to call it.
    All fish can all be caught at different depths,
    at different times but the thermocline dictates the "comfort" zone.
    The density is determined by the lower or in some cases no oxygen content, ammonia content and other gases that are not able to ascend because of higher pressure associated with deeper depths.
    Cold water is heavy and does not rise the same as cold air does not rise. When conditions are right you will notice fog will be heavier and thicker in the lowest places but the density will differ as you can see by looking around.
    Gases also will collect in the lower places or elevations much like fog.

    The shallower water in the coves on the north side of the lake will be the first to respond to solar heating in the spring. This warmer band of water forms around the banks and attracts bait and fish because of it's warmer temps.
    As spring progresses, this band will gradually extend until it covers the whole lake. At the same time this warmer layer will also extend downward. This time of year the thermocline can usually be found at 15 to 20 foot deep in Texas lakes.

    Float fishing is one of my passions and this is the time for float fishing. More and more people are using ballons for this.
    Waterfalls, water outlets, rivers running into the lake and wind and wave action will oxygenate the upper part of the water column especially where it crashes on the rocks.

    In rare cases extremly heavily oxygenated water becomes so light it will not float a boat.
    A high pressure blow-out beneath a drilling rig in the gulf can release so many gases and "lighten" the water mass so much that a floating rig can sink.
    Gases that been held beneath the surface by overlaying formations of rock expands 16X by the time it reaches the surface.

    As the water in the upper part of the column cools in the fall it will reach a realitive temperate stage and the water on the bottom will begin to rise. This will stir up the whole lake and cause it to "turn over" and water clarity will suffer. In some locales, it will be down right muddy.
    This resupplies the deeper depths with oxygen and fish will take advantage of it.

    The deepest depths of deeper lakes will not reach this temperate zone and so will not be affected. Some lakes resort to using barges to pump oxygen to depths of 160 feet in hopes of bringing the dead oxygen depleted deep back to life. Good luck is all I can say.
    There are smaller units available for fish farms and mimi-units for our inhome fish tanks.

    As for fishing on the bottom, as long as the bottom is not below the thermocline, the fish will feed there. That's where most baitfish will be found. Shad are an exception as they are mostly open water fish as are the blues and stripers that feed on them. They will roam up and down the lake.
    Large flats are often caught here in the deepest part of the channel at 35 foot on the north side of my lake. These fish do drop below the thermocline when they are feeding.
    When the water is at normal levels here, that channel is 65 foot deep and we have to wade out to reach it with a cast and then wade back to our rod holders. The rock shelf bank that we set our rods on now, is usually under water and if you step off it while wading, the top of your head will get wet, lol.