Here are some interesting species/size specific temporary oxygen tolerances observed this summer. Temporary is defined as 2 hours or less, mainly because we did apply emergency aeration to improve DO in most of these cases.

I want to be clear in saying:
I am not suggesting a lower limit, only a tolerance
Long exposure to these levels will surely lead to problems
Condello's new signature quote got me to thinking


Most Dramatic
2" Crappie -- .1 mg/liter O2
1"-3" Bluegill -- .25 mg/liter O2

8"-12" LMB -- just less than 1 mg/liter 02
7"-9" Hybrid Striped Bass -- 1.8 mg/liter 02

Thought this might be an interesting tidbit. Could help to explain how an oxygen depletion may lead to a selection of the survivors that contribute to the future fish population.

Maybe it is another good reason not to stock crappie in small ponds. A fish kill could easily wipe out all substantial predators and leave behind a large population of small crappie and bluegill.

There are other conclusions and implications....and other interesting data to be reported I'm sure

That's extremely interesting. So are you saying that crappie were tolerating .1 mg per liter for just a few seconds? Or a few minutes?

Bruce I think Todd means 2 hrs or less as temporary.

thanks for that info todd.....i wonder if there are significant variations between lepomis species. i have read about and seen GSF survive in the absolute worst possible conditions imaginable.

after i put my aeration system in, i could hear my GSF saying "we dont need no steenking oxygen"

Todd's data reinforces observations that the smallest fish are usually the surviors in fish kills due to oxygen shortages. That is good data Todd - thanks for sharing it.

Just as another observation on another species, I caught some yellow cat in my lake and tossed them on the bank after a night of fishing. Two hours later, the fish were still alive and could have survived had I thrown them back in.
Does this mean that cat fish can tolerate even more harsh low DO conditions (low soluble DO across their gills due to lack of wet gills)

Remember - a fish in low O2 water is suffocating; a fish in the air is just drying out slowly.

Fish in the catfish family have vascularated air bladders which means they can extract more oxygen from air than many other sportfish. A small amount of oxygen will move into their blood stream from the blood vessels in and on the air bladder. The result is longer survivability out of water. Walking catfish of fame in Florida are a prime example.

Yeh, seemed almost like the rattle snake I cut the head off of. It "lived" for almost another 2 hours. Spooky!

Correct. Low DO water is a lot different thing than exposure to the atmosphere.

Fifteen minutes with ZERO oxygen for fish is just as deadly as it is for humans. Fish's metabolic need for oxygen is decreased as ambient temperature goes down, but he still needs oxygen. Fish out of water, as Theo says, are drying out before they suffocate.

Good Feedback.

In green ponds one can normally expect lower DO at night and higher DO during sunny weather. Fish can be born with a certain tolerance, learn how to deal with it, or die.

During depletions in loaded crappie and sunfish ponds, the fish hug the top inch of water. Driving around a pond causes the fish to spook, but they quickly return to the top.

Ironic as it is, the most productive southern ponds are the green ones, and the most volatile ponds are also the green ones.

Todd those green ponds are like engines running at high RPMs. Because they are running hard and fast they can be much more volatile and apt to break.

Good Analogy Ewest. Thanks

Fish hug the top of the water because atmospheric oxygen is slowly dissolving into the water as a thin film on top. When the thin surface film becomes saturated with oxygen the rate of diffusion of oxygen into the water under the surface layer is slowed down a lot, thus only the thin film on the very top contains or fairly quickly gets a saturation of DO. Mixing or surface agitation exchanges or disrupts the DO saturated thin film so more atmospheric oxygen can dissovle into the new undersaturated thin surface film. I learned all this when researching my prepared response in the debate about which method transfers more DO into pondwater - plants (phytoplankton) OR mechanical diffused aeration. More on this DO topic may appear in a future issue of PBoss Mag (editor is looking into it for us).

Bill, I'd like to add this to the archived thread on oxygen. Is that OK?

Bruce - It is okay; you can add it.

Guys,

Several years back I got a call from a friend that he was bringing in the biggest bass he had ever caught and wanted to have it mounted. When he brought it in live in a plastic garbage bag, I knew it wasn't anywhere near the weight he thought it was (what else is new with many anglers). Anyway I weighed it on my certified scale and his ego instantly deflated. Said he didn't want it mounted afterall as it wasn't as big as he thought. The gills were still moving although it had been in the bag for a good 20 minutes. I released it into one of my ponds (never would do this now days) and the fish swam off! He survived as I saw him a year later (I could tell it was that fish) as she was much bigger than the other bass in the pond at the time.

The interesting thing about that data to me is the HSB number...the HSB is according to that data at least 8 times less tolerant of low O2 than a BG and almost twice as less tolerant as a LMB of the same size. That data is completely consistent with my observations in which HSB have died in a small pond with no other fish kills....in spite of some saying that it isn't possible.

I would love to see the data for larger HSB. I'm confident it would also support my experiences. My ponds are generally green naturally and summer time temps really drive out the O2 putting the least tolerant fish at high risk....but at the same time, the ponds produce tremendous LMB and BG growth. In ponds, it pays to put the sidewalks where the fish walk.

Bill -- you can't leave us hanging like that?? How about a tidbit? Have you broken new ground on oxygen supply??

Cecil, my first 5# NE master angler LMB went through a similar ordeal in a plastic bag for at least an hour. Back then you had to take your fish to a certified scale to get weighed to in order to get a master angler certicate from our game and parks dept. I ended up releasing the fish in our pond 40 miles from where it was caught. I did have to spend 30 minutes in the water with before it finally got it's equilbrium back, 2-1/2 years later I finally caught the same LMB again when it weighed 8 lbs. I know it was the same fish as it had a unique spawning scar on the top of it's tail that was easily identifiable from the pictures taken then and later.

This data, which is primarily of interest to me as a relative measure and comparison, further supports the contention that we actually know very little(quantitatively) about ponds and the fish within them. There is so much to learn, so much currently unknown.

The data shows HSB to be 8 times more sensitive to low O2 than BG and twice as sensitive as LMB...but the data is against small fish and for very short periods of time. What is the effect on larger fish, I wonder, and for longer time exposures to relatively low O2? I have water temps above 85 degrees for 5 to 6 months out of the year in ponds with high density of pounds of fish per acre (especially during Tilapia season). Does long exposures to high water temps with corresponding reduced O2 levels adversely affect some fish more than others?

Death isn't the only measure of adverse effects on fish, either. Are growth rates in some fish affected by such long exposures? Isn't it likely that there exists an optimum condition, in terms of water quality, for each fish that we consider stocking in our ponds? and further, that the optimum condition is very different for different fish? If we knew those conditions more quantitatively, more precisely, couldn't that possibly result in considerably different stocking strategies than we now have? Obviously, things are different depending on where one has a pond, what the local conditions are, and what the environment is at the pond site. Every pond is different, even on the same physical property. The more we collectively know about optimum water conditions for each type of fish, the better pond meisters we can be.

The more I know, the less I know....makes it interesting for me.