Questions about understanding lakes, thermoclines and oxygen

Discussion in 'Southwest Ohio Fishing Reports' started by spiff, Jan 4, 2008.

  1. Hi.

    I need some clarification. As a fisherman of mainly catfish and occasionally bass and other species in Ohio, it was my understanding that lakes, especially deep ones, have thermoclines and that oxygen levels drop significantly below those thermoclines, say 11 to 15 feet in the summer. In the winter and on the way there, I understand the turning process of warm and cold water.

    So on to the questions.....In a lake like East Fork or another reservoir, how deep can I expect to find fish in the summer and does it differ by species?....catfish, stripers, largemouth, crappie..... Feel free to explain the effects of wind and any other agent that acts on this.....

    What happens to the oxygen levels in the winter time with the turning of the water and where can I expect to find the same species as the cooling process progresses to equilibrium?

    Finally, for the experienced fisherman and/or biologists out there, I don't think I've seen an explanation for spring and the warming of water in a lake....what happens to the oxygen levels then and where do the fish go as it warms.....

    Thanks for you help....tired of making it up as I go...;) There'll be a test in 2 weeks, so pay attention...

  2. fishcrazy

    fishcrazy Muskie Chaser

    I think CC is around 23 FEEt

  3. fishcrazy

    fishcrazy Muskie Chaser

    Doc understands it all, and i would say be glad to help you.
  4. SConner

    SConner Fish Whisperer

    Spiff, I'm not an expert but do have a book that explains this Fairly well - "The Ultimate Guide to Freshwater Fishing" by Al Lindner. After re-reading this I think there is more to your questions than can be covered here but will summarize. In summer oxygen levels are are highest near the surface, so fish not tolerant to low O2 levels may move closer to the surface. Minimum tolerances by species are as follows. Trout 3ppm, bass 2ppm, catfish 2ppm, sunfish 2ppm, walleye 2ppm, muskie 2ppm, white bass/strippers 1.5ppm, crappie 1.5ppm, perch 1.5ppm, pike 1ppm, carp 1ppm, & bullhead .5ppm. In winter O2 levels are highest near the bottom. During turnover O2 tends to be consistent at all depths so fish could be anywhere.

    Here is where it gets tricky - O2 level is only one of many factors that will influence where you may find fish. Others include, water temp, clarity, light levels, food source, cover, etc. Also, reservoirs are less prone to winter kill because in flow maintains higher overall O2 levels.

    Hope this gives some general ideas, maybe someone familiar with East Fork could help you out with specifics on this body of water.

    When you get it figured out feel free to share with all of us. The more I learn the more I realize how little I know.
  5. Nightprowler

    Nightprowler Crappie Hunter

    What is meant by "lake turnover"? How and why do lakes do this in autumn and spring?

    The key to this question is how water density varies with water temperature. Water is most dense (heaviest) at 39º F (4º C) and as temperature increases or decreases from 39º F, it becomes increasingly less dense (lighter). In summer and winter, lakes are maintained by climate in what is called a stratified condition. Less dense water is at the surface and more dense water is near the bottom.
    During late summer and autumn, air temperatures cool the surface water causing its density to increase. The heavier water sinks, forcing the lighter, less dense water to the surface. This continues until the water temperature at all depths reaches approximately 39º F. Because there is very little difference in density at this stage, the waters are easily mixed by the wind. The sinking action and mixing of the water by the wind results in the exchange of surface and bottom waters which is called "turnover."
    During spring, the process reverses itself. This time ice melts, and surface waters warm and sink until the water temperature at all depths reaches approximately 39º F. The sinking combined with wind mixing causes spring "turnover."
    This describes the general principle; however, other factors (including climate and lake depth variations) can cause certain lakes to act differently. A more detailed description of the physical characteristics of lakes, including temporal and density interactions, can be found at the Water on the Web site, sponsored by the University of Minnesota - Duluth and funded by the National Science Foundation.
    Water on the web answers all your qustion and some.
  6. Two other points. The thermocline depth will not be the same in all parts of the lake, and while fish have minimum needs, they also have preferences. Crappie minimum may be 1.5ppm, but prefer 4.0ppm or better. Other factors will affect where they ultimately wind up.
  7. BlueBoat98

    BlueBoat98 Where's Waldo?

    Most of you are aware that lake levels are reported but may not know that the Corps also monitors Temp and O2 in their projects. The trouble is they don't report it often enough. The guy on CJ Brown only does it from about May to October and totally misses the changes that happen in March and April. Here are the links for East Fork. One is graphical and the other raw data. This data was posted in December.

    You will note that while the temp is consistent all the way down, the O2 level plummets at 45 feet. That should mean that there are no fish that deep. If you monitor this data regularly and compare it to your fishing experiences you'll start to get a good sense of what it means for your success.

    See you out there.

  8. Thanks, guys.

    Looks like I need to read a book and a visit a website. I appreciate all of the info. As usual, nothing is simple. Although, the 39 degree density property of water explains alot. Water has to be one of the wierdest substances on earth....expands when it freezes, can get heavier when it warms and when it cools....

    I find it interesting that the O2 ppms per species have been figured out. I started to think crappie were going to be deep until the 4ppm preference was pointed out...which means all species have preferences too.

    So, beyond reading I guess its back to experiences and observations.... That's why I like it.... It's all on me to pay attention and its like Christmas morning every day I never know what you are going to get.

    Thanks again guys...I have to get back to my reading...:)

  9. FYI...Amazon has "The Ultimate Guide to Fresh Water Fishing" for 16.50...down from $24....for that upcoming fathersday or the "honey I don't know what to get you..." suggestion for your birthday, anniversary.....
  10. One other thing; in a lake like East Fork, you can see the thermocline in the summer on a good sonar. You'll also see fish hanging just above it or right in it (it may extend over several feet on your sonar). If it's set up deep, I think those fish may be big stripers, but don't know for sure. I understand that stripers have a higher tolerance for low oxygen water and they like cool water.
  11. does the O2 level get to high for the fish for example Crappie prefer 4.0 but if the water was say 5.5 would they stay were its 4.0 .Would this be the best depth to fish at where the level is 4.0?
  12. Nope; anything above 4.0 is good. I don't think fish don't care how high O2 level gets, although I imagine it doesn't matter once it reaches a certain point; in other words, 8.0 is not twice as good as 4.0; the fish only need so much. After that, it depends on cover, forage, etc. Example: 4.5 with cover and forage everywhere is better than 5.5 and no cover or forage. Reverse it, and they'll be in the 5.5 water.