Pond Boss Forums Thread Like Summary - Lethal DO levels but fish survive & thrive. HOW?

So after a few years of battling, I have now had three years of winter survival from my trout. The problem is I do not understand HOW they are surviving. Not only are they surviving, they are thriving. On 10.05.2018 I stocked 100 Splake that were 5"-8". Iced over completely by 11.05.2018 and didn't fully come off until 06.15.2019. We caught our first Splake on 06.23.2019 and he was 14"-15". Not only did these fish survive under the ice at supposedly extremely lethal DO levels, they doubled in size! For those of you that aren't familiar with my battle, I have never been able to keep a hole open in my ice throughout winter. I'm at 10,000' elevation so a tough environment. I now KNOW the ice is doming up over my diffusers and making it impossible for the aeration to chew through the ice because the water from the plume is no longer contacting the ice. It took a trip up to the cabin this past Christmas for me to discover this doming issue was the problem.

The last two years we have measured a low DO of .8PPM. Measurements have been taken in different spots over the last two years and found the same number. In December 2019 I measured 1.5PPM maybe 30 yards away from diffuser plume. In February 2020 my buddy measured .8PPM. DO below 5.0PPM is stressful for trout. Lethal DO levels for trout is supposedly somewhere between 2.0PPM to 3.0PPM. He also measured .8PPM in Winter 2018/2019. So I am totally confused how my fish are surviving such low DO conditions for an extended period of time. My water temps during these times are 32.5F to 33F.

So, basically everyone on this forum is smarter than me so I'd love to hear some input!

THEORIES:

1. My meter is inaccurate and showing lower than actual.
I am using a YSI Pro ODO DO meter to take measurements. Supposedly as good as they come. A couple things make me doubt meter inaccuracy. We have recorded .8PPM in different years as the low of the year. On 05.23.2020 my buddy recorded DO of 9.2PPM. If the meter was low by 2 PPM or so that would mean my DO currently is over 11PPM. I do not even think 11PPM is possible at 10,000' elevation.

2. Trout are surviving in the diffuser plume.
It has been posted that in near freezing water a diffuser can affect water 200' away. There is some stuff on Youtube (from a guy in MN) that shows under ice water movement from a single diffuser even farther away than that. This year I measured 1.5PPM 60' or so away from a quad plume and got 1.5PPM. Seems unlikely to me that 30' closer to the plume would have led to DO over 3.0PPM. Also seems unlikely to me that the trout would double in size when confined to living in a 30' circle over the plume.

3.I am venting the poisonous gases and that's what would really kill the trout.
I don't have a hole open, but I do think SOME air from the aeration is venting out of the lake somewhere - just not making a hole. I think it is probably leaking out between the ice and the shore somewhere near each diffuser. So maybe while my water is not contacting atmosphere and exchanging O2, it IS still able to vent the poisonous gases like Hydrogen Sulfide?? Maybe in low DO winterkills it isn't really the low DO that kills the fish. Maybe it is the concentrated gases that deal the death blow???

4. At water temps of 32.5F trout are indestructible
You just can't kill them because they aren't even really breathing anyway!

5.God eventually smiles on the dog (me) that hangs on long enough.
I think that one is self explanatory.

I don't understand what you are asking. The exchange of oxygen into the water can only happen in one direction. It can only increase the DO. Organisms using the O2 will lower the DO. But if both are happening, isn't this the answer you are looking for? Could it not be said that O2 dissolving in the water is supporting metabolism? Its obvious that the trout's metabolism wasn't shut down. They doubled in size.

Here's how I look at. The trout could not double in size unless food was available to them. This means that where ever the fish are, so is sufficient oxygen to support them and their food and enough to also support the trout metabolism requirements to double in size. I would suggest this. Next winter, go out with a fishing pole, auger, and a sonar and leave the DO meter at home. Where you find the fish ... there lies the answer to what is supporting them. They will only be in water that provides everything they need.

Just a quick question. Do your trout double in size during the growth season in summer? If not, you have strong evidence that the prey of the pond is concentrated in a smaller volume of water during winter.