I'm not good at short conversations so...

 Recently the lake that I am a member of had a huge fishkill. The lake is pretty small. Hre is a link to see it for yourself www.kennellake.com   Lots of landowners in the area with small lakes and ponds also had the same problem.

 It was while the weather was extremely hot for a long period of time. Late in the hot spell we had substantial amounts of cold rain. The way I interpreted what they said in the paper was that the cold rains kind of caused a very premature very quick turnover. This took a lot of oxygen(?) away and killed the fish?

  Their was predicted that we lost 4,000 to 5,000 lbs of fish in a matter of a day or so.

The lake is mainly for rednecks... I mean catfishermen (same thing really!) but does also get stocked with LMB. In years gone bye when deeper it used to get stocked with Walleye and crappie.

 The bass seemed particularly hard hit. We also lost 2 - 34" Walleye, a 1lb Bluegill, a 35lb Flathead catfish and lots of 4lb cats and 2-3 lb LGMB's

Can someone explain to me in generic terms what might have happened?

We had this at a local lake not too long ago. I am no biologist but here the drought and high temps depleted the needed oxygen , however I do not remeber any catties dying, hope that helps ya.

To kill a Flathead catfish, sounds very bad.  

Very unusual for it to kill a cat. Man you can throw a cat fish on the bank and he will live for a day. It sounds like you had some kind of runoff that poisoned a few of your fish. I can promise you it didn't come from oxygen levels.

Low D.O. or toxic runoff.

      Very unusual for it to kill a cat. Man you can throw a cat fish on the bank and he will live for a day. It sounds like you had some kind of runoff  that poisoned a few of your fish. I can promise you it didn't come from oxygen levels.       [/quote

get serious

I am.

I am of the idea that it was more from lawn chemicals running into the lake than low levels of oxygen.  Though the cold rain may have lower o2 levels than warmer water, the act of it rainning should actually raise the levels of oxygen by stirring up the water that's already there, kind of like an aerator in a live well...

I saw my wife's uncle's pond do this last year. It was full of catfish. It was a DO issue. We solved it by putting in a floating water fountain.

prob low oxygen or bad chemicals being dumped in there

Ok I led us a little astray from the git go. Measurements were taken by the DNR at the time of the kill and it was CONFIRMED that low oxygen level was the cause. Someone had complained of algea buildup in the swim area and thus copper sulphate (?) was dumped into the lake during this time. This further reduced the oxygen level. Further evidence is in the fact that many smaller local lakes and homeowner ponds had the same problem. It would be possible that all of them had contamination but very unlikely.

Note the lake also has 2 air pumps running to help keep oxygen in the water. According to the DNR fish biologists the problem was that the pumps have to be at a certain height in the water column to be effective. They were not at that height.

My only question all along was the mechanics of the cold rain water hitting the warmer water. Why does this reduce oxygen level? What is the science of it?

While I do not know the D.O. of rain, I do know that as the temperature of water decreases, the capability (or saturation point) of that water to hold D.O. is increased.

If you had an algae problem (extreme OUR without light) and solved that problem using chemical addition, you could be temporarily increasing the OUR. As the algae dies and decomposes, it will suck the O2 right out of the water.

Avid went over the side of the boat again, instead of waiting until he got to shore

Avid went over the side of the boat again, instead of waiting until he got to sure

Rain water has very low levels dissolved oxygen (DO). The water column temperature before the rain may have been in the upper 80's and because there was a deep water pump system*, the thermocline may have been very shallow. The result is very low DO levels in the deeper depths where the water temperature was cooler, so the fish were up near the shallow thermocline (first temperature breake between 2 to 4 degrees). The colder rain water is heavier than the warmer lake water and sinks as it cools the upper layers, disspersing what little DO that was available. The fish simply sufficated from lack of oxygen (DO). Usually a windy cold front follows the rain and the wind mixes up water column and raises the DO levels. Must have been dead calm and warm weather after the rain.

The fact that catfish also sufficated indicated that the DO levels were extremely low and and the fish were more than likely very stressed before the rain, due to the warm water conditions, blue stone treatment and low DO at the cooler depths, where the fish would normally relocate.

WRB

* the deep water aeriation pump is there to suspend decaying organic material allowing sun light  and oxygen to further dissolve it and keep the water clearer. However this can reduce dissolved oxygen further without surface aeriation to prevent stratification.

Rain water has very low levels dissolved oxygen (DO). The water column temperature before the rain may have been in the upper 80's and because there was a deep water pump system*, the thermocline may have been very shallow. The result is very low DO levels in the deeper depths where the water temperature was cooler, so the fish were up near the shallow thermocline (first temperature breake between 2 to 4 degrees). The colder rain water is heavier than the warmer lake water and sinks as it cools the upper layers, disspersing what little DO that was available. The fish simply sufficated from lack of oxygen (DO). Usually a windy cold front follows the rain and the wind mixes up water column and raises the DO levels. Must have been dead calm and warm weather after the rain.

The fact that catfish also sufficated indicated that the DO levels were extremely low and and the fish were more than likely very stressed before the rain, due to the warm water conditions, blue stone treatment and low DO at the cooler depths, where the fish would normally relocate.

WRB

* the deep water aeriation pump is there to suspend decaying organic material allowing sun light and oxygen to further dissolve it and keep the water clearer. However this can reduce dissolved oxygen further without surface aeriation to prevent stratification.

Hey WRB first off welcome aboard.

That just re-inforces how good of a site BassResource.com is. No matter what off the wall question you ask, someone will have the answer for you.

Great post that was the info I was looking for thanks!

More complicated than I thought but great info!

To me it also kind of gives you a hint on where to look for fish.

" Late in the hot spell we had substantial amounts of cold rain. "

I don't know why your DNR didn't give a complete clear answer to your question, if they were asked. What happened occurs somewhat frequently following an innundation of ground runoff from heavy rains. Rain has no DO and the rapid mixing of the water dropped the levels in the lake to such a level that the fish asphyxiated.

This phenomenon is usually a smaller, shallow lake problem and more common in the southern areas of the country. However, altitude, time of year, and many other factors contribute to this naturally occuring event.

A good read about DO: http://bcn.boulder.co.us/basin/data/COBWQ/info/DO.html