Pond Boss Forums INTRO Questions & Observations Fish die off, possible cause?

I have a very small pond/water hole, about 60’x75’. Its about 7 years old and all good up until Sunday. It has a few bass and several crappie that have lived there since shortly after construction. They both reproduce. Sunday I visited and found about twenty dead fish, all about 2-3” long. There were plenty of other same size fish swimming about normally. Also saw a couple of the bigger fish as well. Here in SE Georgia we have an abundance of rainfall this winter. Pond water is clear and steady running out the standing drain.
Any ideas on a cause for the dieoff?

Thank any replies.

Welcome to Pond Boss!!

If there was as specific episode of heavy rains, there's a chance that the 'bad' water from the bottom could have mixed with the 'better' water near the top.

How deep is your pond?

Let's see what others have to say.

Pond depth average about 2’, max depth about 4+’.
We have had mucho rain since last fall. Last two weeks we had at least 6” near the pond. Some of the rains have been heavy 2-3” that caused some erosion and washouts. Main drainage/seepage into the pond is well vegetated and I did not observe any erosion into the pond. The water is very clear throughout. It could have mixed the water but I am not sure a temperature gradient really exists or that there is stagnant water. Water has been running through the standing drain for over 4 months continuously.

Thanks for the reply. Just puzzling to me.

Wetlands of that depth often have low oxygen events that kill off fish. We have a few wetlands on our place like that where we have had fish kills in hot weather, but they get very little direct runoff (mostly spring fed). A couple of these get flood water from a stream every ten years or so and repopulate (although the green sunfish never seem to get completely killed off). One time we had a bunch of nice-size warmouth going.

Anyone have any further input for GeorgeShu??

With that shallow and size of a pond things can change fast. If you got a lot of rain or wash in then you could have had a DO (oxygen depletion) issue. Also if the pond is fish crowded and O is low the demand can be higher than the supply. What are your water quality parameters?

Always difficult to diagnose a fish kill event with so little information. Reason 278 to buy a 25 dollar test kit and thermometer and chart water parameters once to twice a month. An extra 50 gets you a simple DO test kit. I know what my water test parameters will read before I even do the test. If they aren't what I expect, I reconcile issues before there are floaters.

Thanks for the comments and ideas. Since last post we had almost 4”rain weds and thurs. Most likely the problem is low oxygen with all the added inflow.

Will find a test kit and start recording results. Great idea!

Thanks again.

Is rainwater void of dissolved oxygen?

Nope! But if there is sufficient rain, it can quickly change the pH or temp of a pond, and that shock could kill some fish.

yup