Oxygen Level, thermo cline during winter and walleyes

[DarkLordoftheEyes]

I recall reading a pro's tip about oxygen level, thermo cline and how it relates to walleyes during summer. Has any one seen an article relating this to winter? I am sure someone has and hope someone points me in the right direction. Thanks

[pathogen]

I don't believe there is a thermocline in the winter. That's why walleyes can sometimes be caught at depths in the winter that they can not use in the summer. Oxygen can actually become depleted in the shallower water first due to decay of organic matter and use by oxygen breathing critters.

[Bob_D]

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I don't believe there is a thermocline in the winter.

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Pathogen is correct. There is no thermocline in the winter under the ice.

[Minnetonka]

In the winter the formal term is "Inverse Thermal Stratification". This means that the water just below the ice is at 32 degrees F or 0 degrees C. The water is warmer as you go deeper and at the bottom, the temperature is approximately 38 degrees F which is the maximum density of water. Sunlight through the ice, ground water intrusion(springs) or current can influence the stratification of water both in the summer and winter.

[Bob_D]

It's actually 39.2F (4C), but 38 is close.

[Fish&Fowl]

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In the winter the formal term is "Inverse Thermal Stratification". This means that the water just below the ice is at 32 degrees F or 0 degrees C. The water is warmer as you go deeper and at the bottom, the temperature is approximately 38 degrees F which is the maximum density of water. Sunlight through the ice, ground water intrusion(springs) or current can influence the stratification of water both in the summer and winter.

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Along with this, most of MN's lakes are dimictic, meaning they turn over twice (in the spring and in the fall.) During these turnover periods, water is mixed has equal temp. and oxygen levels. Once the thermocline does set it, water below it can change as much as 1 degree celcius for every meter. The deeper you go, the colder the temp. and the lower the oxygen level.

A good rule of thumb for where the thermocline sets up, but not always, is where 1% of the surface light is getting through.

I certainly am no expert on thermoclines but we just got done going through all this in my Ecology class. It's nice when we cover stuff that's actually interesting!

[Sonicrunch]

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The deeper you go, the colder the temp. and the lower the oxygen level.

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Question.

Cooler water can hold more gas than warmer water. So, why does the colder water near the bottom have less gas? Is it because it is father away from the surface?

[Swimmer]

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The deeper you go, the colder the temp. and the lower the oxygen level.

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Question.

Cooler water can hold more gas than warmer water. So, why does the colder water near the bottom have less gas? Is it because it is father away from the surface?

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One reason, as explained above, the most dense water at 39 F, at the bottom, is the warmest in the water column. And, I don't think it necessarily has less "gas", just less oxygenated gas. In other words, the decay process on the bottom eats up oxygen and produces CO2; and anaerobic bacterial processes produce Sulphur Dioxide; both of which would tend to replace the gaseous O2 in the water. This is why we typically see, at least with the Ice Machine, bubbles rising horizontally on the screen.

[Sonicrunch]

Sorry, I was referring to Summer water. Cold on bottom, warm on top.

[chris63]

Alrighty then can I fish now? c63

[DarkLordoftheEyes]

I wasn't sure this topic would get any attention. Thanks for the updates. So should I pay more attention to temp or doesn't it matter during winter if you are fishing your bait 6-12 inches from the bottom?