Time to start watching DO charts

[Phil Lilley]

http://www.swl-wc.usace.army.mil/WCDS/Repo...rofiles/do2.txt

http://www.swl-wc.usace.army.mil/WCDS/Repo...rofiles/do1.txt

Each year in the fall, our tailwaters experience a 'natural' occurrence. Our lakes stratify (separate into levels of density and temperature) and cause "less than desirable" water to flow into their tailwaters. Each tailwater is alittle different as to severity and timing but the bottom line is that dissolved oxygen levels plummet to the point that either liquid o2 is added to sustain life or operation of the turbines is adjusted to achieve the same result.

The problem is the Corp only has to keep the levels at minimal levels, barely enough o2 to keep our trout alive and active. We see fishing slow down at times as well as after hooking some trout, they roll over and give up easily, "no fight in the dog".

These charts are worth looking at occasionally. I wouldn't gage a fishing trip by them because they can be alittle deceiving.

A couple of things to note- sunlight adds o2 to water- so does wind. At night, the level will drop to their lowest and early morning you'll see it bottom out sometimes. Also, when fighting a trout, especially a big trout, you can literally fight the fish to dead if it's not landed quickly and released carefully. But sometimes a big trout will die after being caught no matter what you do... it just happens. That's why I suggest it you foul hook a big trout, do not fight it to the net- break it off! If you're upset about losing a bug- come by the shop and I'll replace it. I'd rather give a couple of flies away then see a dead trophy on the bottom of the lake because some knot head didn't want to lose a sow bug.

You can find these links on OA's Useful Link Page here - http://ozarkanglers.com/useful.php

[Danoinark]

Excellent suggestions and right on. I think low DO is probably more devastating that higher water temps.

Dano

[Don]

What are the optimum as well as dangerous oxygen levels for tailwaters?

Thanks, Don

[Danoinark]

Don

If you look at the pinned guage information say for Taneycomo, you will see that the Corps biologist have set a minimum of 5 and a optimum of 9 as anything in between being appropriate DO for trout in Taney. It will probably vary for other tailwaters....Dano

[Luke]

Dano - Are you sure that's correct? I read the chart as saying the Minimum DO for the day was 5.0 mg/l at 6:00 am on the 29th and the Maximum DO was 9.0 mg/l at 2:00 pm on the 28th. I could just be looking at it wrong, but it would be nice to know for sure.

[Danoinark]

Dano - Are you sure that's correct? I read the chart as saying the Minimum DO for the day was 5.0 mg/l at 6:00 am on the 29th and the Maximum DO was 9.0 mg/l at 2:00 pm on the 28th. I could just be looking at it wrong, but it would be nice to know for sure.

Luke after rereading the guage info, I think you are right. I apparently misinterpreted what I was reading. I checked all of the others tailwaters and that would confirm what you are saying. Now I do know that when the DO on Norfork gets in the range of 3 and below it seems the fish are very sluggish. I am assuming you can also have to much DO also. Will be interesting to find out a firm answer. I bet the folks at the hatchery could shed some light. Dano

[Luke]

Any idea what "Table Rock vents are open" means? It says this at the bottom of the report.

[Danoinark]

I talked with Bill Murphy the assistant hatchery manager at Tablerock and he was very informative about the O2 requirements. He says alot depends on the size and quality of the fish, but he thinks 5 parts per million of do is the low end of the spectrum. Although that doesn't mean the fish would be adversley effected at some levels below 5. He says he gets concerned at the hatchery if it gets below 6 and will increase the O2 content by adjusting the flow of the runs. He says in a natural environment like Taney there is no concern over to much oxygen. As to the "vents" Bill says the dam has ways of taking in air (atmosphere) and using that to help increase the O2 or they can use liquid O2 for the process.

Bill was very nice to talk with about this and extremely knowledgable....Dano

[Luke]

Dano - As always you are very helpful. Thank you very much for finding out the answers for the rest of us.

[Don]

Thanks Dano.

I've been researching the web via search engine articles. In one article I found 5mg/l was listed as a necessary O2 level for raising trout. Also, Arkansas Game and Fish conducted a study on the White years ago and listed at least 6mg/l as a recommended goal, especially during spawning season for browns.

Thanks Don