Good evening pond boss community,

I have about a 1/2 acre pond 12-14 ft deep in North Central Iowa. Over the last 3 weeks or so every day I've gone out to the pond I've found another 1 to 5inch fish dead along the shore. I walk the pond every morning around dawn and then 3-4 more time periodically throughout the day and I see 1 or 2 fish dying every day, I haven't seen more than 2, and have only had a day or 2 where I haven't seen any floating. They have all been green sunfish < 5 inches in length until today and then I did find a 3-4 inch perch dead along the shore. I haven't seen anything larger than that and haven't had any catfish, walleye, crappie or large GSF during this same 3 week ish timeframe.

I purchased the property back in march, the pond had about 5 big grass carp, and countless Channel Cats and GSF. Nothing else. So we pulled around 50 catfish out and I stocked 100 3inch perch, 100 crappie 2inch, 25 walleye 5-6inch and a gallon of fatheads back in May. Then added another gallon of fatheads, 70 1.5 inch SMB and 100 1.5inch Redear sunfish in June.
I run the 3 aerators at night typically so I don't superheat the pond and we were feeding about 1 cup of sportsman every evening.

Everything was fine up until the beginning of August when the GSF started dying. It's been a weird year, we had so much rain in the spring that the water actually rolled over the berm by about 4 inches and now we've basically been in a drought < 1 inch of rain since june and the pond has lost 12-18 inches of depth. So I ran the well and added a couple inches of water back into it thinking maybe that would help with the die off and I've been running my 3 aerators 24/7 after the first week of the die off, but nothing has changed, I still go out every day and see 1 or 2 dead. Today was the first perch I've seen so I decided it was time to ask if anyone else had run into this or if there is something else I should be trying? We stopped feeding them about a week ago as well.

I'm kind of at a loss as to whether or not I should be concerned, if perhaps this is just a random stress event perhaps or if it's something I'm doing? Is it just that time of year when the weather is weird and the fish are stressed to the max and I just need to kind of wait until it cools off more in September and revisit the situation?

Everything I've found on this forum/searching google seem to indicate if it was D.O. levels that we would see a pretty dramatic event, 10s of fish dead at a time, not this weird slow die off.

Let me know what y'all think.

Best
~K

Do you see any fuzzy-type fungus on any of the GSF or the perch?
What is your surface temp am and pm?
I might add there is a good chance your SMB became food rather quickly with 5-6" WAE stocked 2 months ago-those fish and the crappie have likely gained a couple of inches since then. 1gal of FHM is 1-2 days worth of food for that many fish.
OK, I see those added in june. Still likely they became food for others quick.

I see fatheads along the shore every night, so I don’t think they’ve been eaten and I trapped a red ear a few days ago so I think there’s a chance they haven’t all been eaten. The walleye are already 10-12 inches they must be crushing the gsf. I haven’t seen any kind of fungus on the live or dead gsf. The surface temp at the end of the day is way up into the 80s, still warm in the am as well it hasn’t been cooling too much at night maybe into the mid 70s.

Low to mid 80's isn't terrible as long as the entire water column is not mid 80's with low DO.
I have seen some populations stress to a point fungus and other problems pop up but the fuzzy looking saprolignia is most common. If that's not the case, I'm not sure.. Many variables involved. GSF are extremely tolerant of lower water quality and are not normally the first species to show up- but also, not all dead fish float. YP tend to hang out in deeper, cooler haunts compared to GSF this time of year which tend to be more littoral (close to shoreline) habitat.
I'm sure some of the more in-depth, experienced members may have some ideas but I can't say what might be going on.
I don't think it's anything you've done.

EDIT: You haven't noticed any damage or puncture wounds on any of these fish have you?

In July I saw A couple gsf that looked like walleye took chunks out of them but these ones haven’t had any wounds. There are soy bean fields around the pond I’m wondering if when they’re crop dusting if there is some getting in the pond...

I suppose anything is possible.. Beans require several applications of copper and Sulphur to slow the natural maturity process (Blight).. Not sure that would cause an issue but other insecticides sure could.

I am not positive when it comes to how long does it take a dead fish to start floating but i think it is around one to 3 days and even after that all the dead ones don't float. The reason I bring this up is from my experience when I doubled my aeration run times it sometimes killed a few fish like going from 12 hrs to 24 hrs it might kill a few fish. I also one time experienced where I found a few dead small bg almost every day. I had added a different size fish food and after I did I started seeing some dead bg floating. I was where you are at and could not figure it out until I realized maybe the fish were choking on the feed. These dead fish were in the 3 to 4" size or maybe even a little smaller. I stopped feeding that sized feed and the fish stopped dying. Is it possible the feed you were feeding was choking the smaller fish? It does happen. Any chance it has the combination of things that are killing the fish?

Hmm it is possible the food chunks are kind of large. I’m going to give it a few more days with no food and no aeration and see what happens. I’m just hoping no large fish start dying we are about to have a 95+ degree stretch so that is concerning.

Chunks missing could be turtle bites after the fish died, walleye won't take chunks out like a shark or wahoo. Seems that most of the fish in the pond are smaller, and a GBH (Great Blue Heron) would eat them vs. just stab them and leave them like they do with larger fish.

I wouldn't add any more fish to the pond, your pond will be VERY fish heavy once they start reproducing. When you put the aeration system in, what was your start up procedure? Can you go out in the pond and take a temperature reading from different depths? If you go swimming out in it, is there a big temp change below 7-8 foot water depth?

So I didn’t put the aeration in, it was all here when We bought it, there is one at the deepest point any 14 ish feet and then 2 more in the corners at probably 8 ft. I don’t have a thermometer that I could check the Temperature at different depths and I’ve never swam in it. By chunks I just meant like teeth marks not shark bite marks.

Any thoughts on other stuff I should try? Haven’t seen anything dead along the shoreline today so far.

If something is killing your GSF but sparing the walleye, I would like to know what it is killing the GSF. They tend to pretty tough. In Oklahoma, they inhabit shallow pools in intermittent creeks that are completely shaded by trees. So they are pretty tough as far as DO goes.

It may be possible that the few you have seen are aged individuals that are dying of natural causes to which they are more vulnerable due to age. Don't know but this might explain why GSF are the only observed deaths. In any event, a GSF may not likely survive a walleye's bite even if it escaped the being eaten part. So if most of them had evidence of predator strikes, this may explain their exclusive appearance as well?

Well, not all the GSF have had teeth marks just a couple early on. Since I’ve turned off the aerators a couple days ago I haven’t had any dead fish. I’m not sure why but I’m going to continue to monitor the situation and see where I am in a couple weeks. Maybe I was super heating the pond with the 90+ degree days and that much aeration power in the small pond just started causing turbulence and heat issues.
Thanks for all the input folks.

I talked with one of our biologists this am and he thinks if GSF are the species showing up (mainly), he believes it's a water quality issue that has allowed a potential disease to take hold in a few specimens..
He mentioned SMB are also subject to a couple of the problems that will affect GSF but usually show up much later in lower number if serious enough. He also stated most of the fish you would see would be the smallest sizes present and didn't think a fish or 2 a day represented any action was warranted at this time.
I'd say keep an eye on things.

Just a thought...you said you started adding wellwater. Have you used this well water much or any before? Have you ever had that well water tested? I don't use my well water even though I thought it was GREAT I had a well but...the chemistry was horrible! I used it to water a garden one year...killed everything. Used it to water peach trees and fig trees...killed everything!! No way I'm chancing it in my pond! Just make sure you have good pond water. Good luck.

I meant to write...just make sure you have good WELL WATER.

Thank you for reaching out to your biologist that’s a bit relieving. I’ll check the well water quality, that’s possibly an issue the old owners used it to fill the pond, but they didn’t really care about the fish.

Generally, the cost of electricity makes filling a pond an expensive idea. In my case, my well, when drilled, produced 1/10 gpm. I expect it has improved. I'm pumping it into a 4,000 gallon tank so it is fine for the house but I couldn't even have much of a garden.

According to Lusk, only a small % of dead fish float.

They weren’t really floating so much as washed up on the shoreline, so hopefully it wasn’t a bunch more at the bottom. I haven’t seen any for three days now so hopefully aerating less is helping.