low oxygen levels in lakes

[blanked]

i dnot seem to hear about this much.  why look for structure in deeper water if low oxygen is an issue.

then again how do you know if there is low oxygen.  is it common .

[steveperry]

Deeper water is colder, and it holds more disolved oxygen.

[rbrick]

Here in Tallahassee we are in a severe drought which is causing low oxygen levels.I like to fish the small lakes in the Appalachacola National Forest.These lakes have no springs or creeks feeding them.The underlying bed is clay so there is no way for the water to escape.

The hydrilla has completely died off.The lillypads are getting sparse and it is almost impossible to catch a bass (although the pickerel seem to thrive in this lifeless water).If you are lucky enough to catch a bass it seems to have no energy to put up a good fight.

I'm thinking it may be to late for some of these lakes.I think the only way to oxygenate these lakes is to get a lot of rain and get it fast.

[Taliesin]

Deeper water is colder and "normally" will hold more O2, but in the heat of the summer a thermocline will set up. Below the thermocline the water will be much colder, but will end up O2 depleted because it's all been used up and the water isn't moved enough for it to get to the surface and be refreshed.

The problem here is different definitions of deeper water. To most bass fishermen "deeper water" is anything over 10 or 15 feet deep.

Catfishermen worry more about the thermocline becuase they think of "deeper water" as 30 feet or more and the thermocline is normally around 25 to 30 feet deep.

It will not happen in water with a good flow (rivers and streams). It normally only happens in larger lakes where the water doesn't move much.

O2 depletion isn't an issue when the thermocline initially sets up, but becomes an issue when the fish have used up the O2 down there. If I remember rightly, most lakes don't worry about it until close to mid-July.

A really good depth finder will show a "false bottom" at the level of the thermocline as the sonar is partially bounced back by the temp change.

If you are fishing a body of water that "turns over" in the fall, you've got one that will develop a thermocline. The turnover is when the water on top cools off and becomes colder than the O2 depleted water, so they switch places.

If you really want to know about the thermocline in your local waters, talk to the really successful catfishermen around there. They can tell you how deep it is, when it sets up, when it becomes depleted, and when the turnover normally is.

[boatnik13]

Without going into deep science let me just say this> I don't know what the depths of your lake are or any general make-up. So here is a example since I work with this subject. Fishing a manmade lake with maximun depths no grater than say 40 ft. OK!

I don't find thermoclines here in July and the water is like a bath tub. Testing the temp. we have cold water at the bottom and warm on top. NO ONES CATCHING FISH!  I test the D.O. with a meter and find that water below 20 ft depths is from 2ppm D.O. to 0 D.O.  meaning that the depths are "DEAD SPACE". We know the fish are in the lake! I know that I need 4ppm D.O. min. for most game fish and ideal would be 8 or 9.  Searching the upper 15 ft. depths for D.O. of 4+ was the key. I located 1 spring and a few weed lines at 9 ft. depths that so many didn't know about. Getting now a 6 to 8 ppm in certain locations spells fish. Next I use a underwater camera and there are the fish. It doesen't mean they will bite but I found there "'COMFORT ZONE". I also found a compressed zone at a depth of 12-16 ft. depth that host suspended schools of fish. Yet I got people telling me there are no fish . CATFISH,CARP & SUCKERS can withstand low D.O. rates for long periods of time and still be active but not bass and other high energy fish.  Conclusion> Finding fish is half the fun, but doesn't mean they will be bitting.

I make maps and show the productive area's and what your talking about is common and happens alot on hot dry weeks. Your answer> Yes! find structure in there comfort zone and you WILL increase your catch. Structure in the dead zone will not produce.

[Taliesin]

I don't find thermoclines here in July and the water is like a bath tub. Testing the temp. we have cold water at the bottom and warm on top. NO ONES CATCHING FISH! I test the D.O. with a meter and find that water below 20 ft depths is from 2ppm D.O. to 0 D.O. meaning that the depths are "DEAD SPACE".

That 20 ft mark is the thermocline I was talking about. While you may find a few fish below that mark, they won't stay there for any length of time at all.

Hmm... Wonder where I can get a D.O. meter? We end up with some D.O. problems sometimes.

Just in case you haven't heard the term before (it took me a bit to remember it): D.O. is Dissolved Oxygen

[Bassinfreak2]

I also wonder where I can get a D. O. meter. Any members know?

[boatnik13]

in my story the thermocline did not produce fish  and thermocline was not present by  use of electronic testing  but the D.O. was at 4-5 ppm  at the 12 - 16 ft. depths it did have fish in  pockets.  The 12 ft was just out of range of the 8ft. sun penetration  (secchi disk tested) and the varible was 4 ft.  This was the compressed zone (12-16 ft) (@ 4-5 ppm D.O.). The weed line at 9 ft. depth produced a 8ppm D.O. and the spring at 8-9 ppm.      How do you get a meter? I got on line and serched but I also got one from Bass Pro online. Prices can range from $40 to $200 on the net depending on the quality.