Just got back from South Texas and saw some big bass dead on the banks of 2 different tanks. 4 of these were over 5 lbs up to 8, i'm guessing. Is this due to lack of oxygen? Can anything be done to save the rest of them. Very sad sight.

Not really, I have heard of running an outboard in place to pump oxygen in but its not pactical. Also heard of dropping the tractor shredder into water same purpose. Temporary fix at best.

Its hard to say for sure if its lack of O2...these strong winds serve to add significant amounts of O2 to the water through wave action....don't know if south Texas is getting these winds or not....but if they are, the cause of the fish kill may be due to the lack of flushing fresh water to carry out the build-up of wastes in the pond....and/or low water levels that simply can not support the pond full fish population.

Poor water quality seems to always affect the larger older fish first.

Yes, its a sad thing...but if we don't get some rains, its a sight that will be repeated many times over in many Texas ponds as we continue into the hottest part of summer.


p.s. I sure would think about suspending artificial feeding, if its being used, or at least cutting it way back.

There really is some truth to using the outboard or shredder to agitate the surface water. This will increase the oxygen levels quickly, but temporarily. It is all about making the surface water touch the atmosphere as quickly as possible. You can do the same thing with a surface aerator or a paddle wheel (what we use at fish farms). These systems are good for emergency situations.

The key to avoiding this situation is to understand what is actually causing the oxygen shortage. Below I will provide a diagram of a common Texas lake during the summer and stratification. Stratification marks a sharp temperature or oxygen change in a lake. Above the thermocline there is warm oxygen rich water. Below the thermocline there is colder oxygen poor water. This bottom area is usually influenced by waste. As waste increases at the bottom of a lake the oxygen level will continue to drop to zero.
[img]http://texasprolakemanagement.com/uploads/2/8/4/7/2847010/5632911.gif?693[/img]

The stratification of a lake becomes a problem when a cold front hits, during a heavy thunderstorm, or when water levels drop during a drought. During these weather events the surface water cools and causes rapid mixing, which brings the toxic bottom water to the surface. The toxins can kill the zooplankton and fish, taking up even more oxygen. Depending on the severity of the turnover, fish may start dying from lack of oxygen. Usually, the oldest and largest fish die first.

If stratification has become extremely sever oxygen shortage can happen overnight. As phytoplankton do not produce oxygen during night because of the lack of sunlight. If an oxygen shortage occurs over night usually the owner will see many dead fish with little to no signs of cause, as oxygen levels can become normal quickly after sunrise.

For a long term solution you need to get a bottom diffusion aeration system installed in these lakes. Aeration is done by using compressed air to continuously move large volumes of low-oxygen water from the bottom to the surface of the lake. This circulation will increase oxygen levels from the top to bottom of the lake and eliminate the stratification in the lake.

There are many other benefits to aeration systems which I would not mind discussing with you if your interested.

Here is a very helpful link about aeration: http://thelakeexperts.com/

Well this is interesting, we just had severe weather 2 weeks ago, strong thunderstorms and 2.5" of rain in less than 2 hours. The level rose about 2' in the tanks and it was after this I found the dead fish. I would assume the 02 levels are better after the influx of fresh water.
The wind has been very high all spring. Thanks for the input.

That sounds like a lake turnover.

Could be a turnover and aeration is about the only thing that possibly could keep it from happening.

Bigger fish always go first during an oxygen shortage.

Question, only a few large bass found dead, or were there other sizes and species of dead fish?

Although larger bass will expire before smaller ones in an oxygen depletion, if that were the case you'd expect to see some other species and/or sizes of fish.

The only thing I see that kills large bass and leaves all else untouched is largemouth bass herpes virus.

One indicator to look for is the mouth. in 99% of O2 depletions the jaw will be locked open. but they have to be fresh dead, within a day or so.

I'm glad this topic was brought up bc I have a question about a bass lake right on the border of Mexico. Used to be a big lake, 25 acres or so. This lake is not fed by anything but runoff. The lake was about 15 ft water depth before the drought with a healthy population of LMB. Biggest caught was over 13 lbs and a few more over 10. Now the lake is approximately 2 acres and reduced to 6 ft depth and I am wondering if any of the larger fish would have survived since the fish that I do catch are no larger than 15 inches and are extremely unhealthy. I figured that maybe the larger fish would feed on the smaller ones since I catch a fish literately every cast. The delima is whether or not to pay the expense to remove the fish if there is the potential for larger fish surviving the drought and moving them to another property.

Another interesting point is that I have never seen a single dead fish around the outside of the pond. Granted we have many predators in that part of the world.