Pond Boss Forums INTRO Questions & Observations Dropped DO from??

First time poster, I appreciate all of the knowledge that is shared on this forum. I have learned a ton in a very short time. I have a 1/2 acre pond that has an average depth of 8 ft just south of Kansas City. Wednesday night when I went out to "scout" around the pond I discovered multiple floating channel cats. I'm certain this is from inadequate DO, what puzzels me is how this happened. I fed the fish Tuesday evening and had "good" activity. Tuesday's high was 100+ degrees and Wednesday morning the temp was 54 degrees......did this have something to do with my DO drop? Normally there is constant flowing water to my pond, this has dried up in the last week from lack of rain. For two weeks prior or so it was "flowing" at a rate of 1 gallon/hour or less. Is that more of the culprit? Or is there something else that I'm missing? Any insight would be great. Thanks.

I sure like that screen name. I'm not trying to be rude but I have a few neighbors, ( pond rippers ) that have the same name. I guarentee that you will be satisfied with the real pond people on this site. Good Luck to you.

When that cold front moved through did you have any rain? This would be an important factor. It sounds like you didn't, but sudden changes in temperature can create a turnover effect. Usually in the fall, cooling surface temperatures from cool rains, cold nights or high winds make a pond "top heavy" for lack of a better term and you have a sudden mixing of the stratified layers of a pond. This mixing brings organic matter and anoxic water from the bottom up into the water column and you can see some mortality. I'm not aware of a turnover that would occur this early, but that cold front was unbelievable! Our air temperatures in Lincoln dropped 24 degrees in 50 minutes.

I am not an expert in treating or diagnosing pond fish kills BUT I am trained as a biologist. By understanding the common causes of summer fish kills it may help you diagnose the problem.

The most common cause of oxygen depletion is a die-off of macro and microscopic plants. This is most likely to occur during hot overcast weather. During this type of weather photosynthesis can be inefficient and plants often consume more O2 then they produce. Eventually they begin to die and decompose further depleting O2 levels. Could the small stream have been providing nutrients to your plankton? Did you notice a dieback of plants?

Another cause is a water overturn. Water can become stratified in the summer. As the temperature difference between the bottom of the pond and the air increases, wind is unable to mix the layers. The upper levels contain O2 while the lower levels will have very little. A tremendous rainstorm or something can mix the levels and cause depletion. Could the decrease in in temperature Wednesday morning have allowed some mixing of the layers? Was there also a strong wind? I would guess that if a pond was the susceptable to stratification it would be severe this summer and a few hours of cold weather could not be a problem but the theory is fascinating.

Don't forget to rule out other causes of fish kill like some pesticide/chemical runoff or disease/parasites.

A question for others who reply; is it unusual for catfish to die first? Generally they are considered tolerant of low O2 levels. On the flip side, the largest fish generally will die first and they may have been the largest.

Good Luck

Bruce, We did have a little rain. Just under .25 inch that came very slowly.

How high were the winds and how deep is the pond?

No wind. Avg depth of 8 feet. Deepest area is 12 feet.

The Channel Cats are the largest fish in the pond. As far as any other dieback of plants, they all seem to look fine. I'm not sure if the stream was providing any nutrients to the plankton or not. I must plead complete ignorance to that. How would I know/test for the nutrients?

I can't believe BASStard has not credited me for saving his pond, especially after I gifted his subscription.

Returning from a small state fishing lake yesterday, where I was breaking in a new outboard, I received a distress call from BASStard saying that his catfish were dying. I immediately detoured to his house, because that is the kind of guy I am, also I was out of beer and he never is. Backed my boat into his pond and did some outboard aereating. Not sure if it did any good, but hopefully we didn't hurt it.

BASStard's pond is in a rural subdivision and drains several pastures and lawns, lots of nutrients. Pond is minimally 50% covered with pond weed and algae. Both Bruce and Jayman present valid reasons for low DO. I think drastic temperature swing contributed to turnover, also 10 days of 95+ temps contributed to decaying vegetation and DO depletion.

What is kind of puzzling is that none of the bass, bluegill, or grass carp were sucking air.

You can make an assumption based on what is uphill. Pasture, fertized crops, etc will provide nutrient run off. For better or for worse.

The fact that this stream is not flowing contributed to the fish kill. How much it contributed it hard to tell. At the very least it was providing a source of fresh aerated water.

I know someone here is an expert on this. I believe that catfish (no scales) are more susceptable to certain diseases and pesticides. Some of the things people put on thier lawns can kill anything.