Pond Boss Forums GENERAL QUESTIONS Help 2- 4- D Run off?

Over the last week I have had about 100 small minnows,perch and bass die and four medium perch and one fifteen inch walleye die. I have been racking my brain to figure out what's going on. One thing I thought about is that about three weeks ago I sprayed my lawn with 2-4D weed killer. I read the label and it said it's toxic to fish. has anyone had any experience with this? The good news is I still see plenty of small fish active in shallow water and it appears for now anyway the larger fish haven't suffered too much.

I think it is safe to say that the fish mortality is unrelated to your 2,4-D lawn-treatment. Beyond that, I really can't speculate as to what else might be the culprit.
Indeed, 2,4-D labels make the statement "...may be toxic to fish and aquatic invertebrates". However, the intent of that statement applies to extremely high concentrations (ie spills, excessive/over-appliations, etc). Label-sanctioned aquatic treatments, and labeled turf-applications, are not indicted as a direct threat to fish (though they could possibly represent indirect-threats due to DO crashed).

In my pond this year I've noticed small (2") LMB floating dead after the rains that we've been having. No rain for 3 weeks, then we get an inch or so. I can only attribute it to a rapid water change (pH, temp or ?) where my small fish were in the shallows.

What else has been done to the area around the pond in the last few weeks before the rain?

Cold summer rains followed by cloudy conditions can result in low DO and fish kills.

I had a biologist come out today. He checked DO and temp and said the whole pond was uniform top to bottom. I showed him the chemical I used on my lawn and we saw that in addition to 2-4D there was another chemical in there so he checked with the EPA and found out that the stuff I used on my lawn wasn't the problem. I have three field tiles that drain into the pond and he thinks this could be the problem. I have my doubts because this time of the year there isn't any chemicals being used on the fields. Also it only seems to be mostly perch, walleye, and minnows dying with a small percentage being large mouth bass no crappie or bluegill. The biologist looked at some of the dead fish and they appear to have nothing wrong with them. He would like to send a fish to be tested, so I found one that wasn't quite dead yet and put it on ice.

I'll be interested in what the results of the test are!

What is (was) grown in the fields within the pond's watershed?
Also, are the drain-tiles beneath a public road?

Corn and soybeans are in the fields. I don't know where the tiles come from. The farmer next door said he had a map but couldn't find it. The thing I don't understand is why hasn't it killed off other species? As of today I have collected 10 large perch and 4 med. walleye and hundreds of 2-3" fish. When I look in the shallow water I see lots of small fry that appear to be healthy.

Just for grins, check your pond for macro-invertebrates or insect larva - particularly near the area where the tiles funnel water into the pond.
I'm thinking IF there's a contaminant (carbamate or organophosphate insecticides, at fish-lethal levels), the macros and insect larva would likely be absent. But, if live specimens are present, the probability of an insecticide contaminant would be slim.
This is simply a thought, and not based on prior experience.

After dropping an underwater camera in the pond I think all of my perch and walleye have died. I talked with the biologist that was going to test the fish and he concluded that I had a DO crash. He thought testing the fish would be a waste of money. (about $1000) I could possibly buy into that therory, except for the fact I found new dead fish over about a 7 day period and minnows also died and as of today continue to die. Any sort of toxins that would have gotten in the water would have killed other fish also. I was told to test the water we've got to have something to test for.I think I'm going to get about a dozen perch that are pellet trained and put them in the pond and see what happens. The water temp has dropped quite a bit and should hold more oxygen. I think I'm going to start looking for an DO meter so I can monitor things better next year, Any suggestions?

A university extension agent stopped out to look at my pond. After telling him what all happened he concluded that when I had a fair amount of my pond weed die off and sink to the bottom and start to decompose I had a DO crash. But he said that wasn't what killed the fish. The reason why the fish died over the course of a few weeks was because their gills were burned by the hydrogen sulfide from the decomposing pond weed and when the do crash occurred the gasses became trapped. He said when fish have their gills burned it doesn't kill them but stops them from eating. He also speculated that I might have lost all my fish, which I can't confirm. I put in 24 yellow perch that are pellet trained to see what happens, the only thing is I can't seem to get them to eat.

Anyone else ever heard of this ?

KENZ, no offense, but your extention agents thoughts here and on your aeration post give me real pause to wonder about his knowledge. His possible cause for fish death is plausible on it's face and "sounds" good, but the reasons he gives do not make a lot of sense.

Most fish can live months without eating so that is unlikely to kill them. I think if the gills were "burned" there would be visible proof and the fish would die rapidly from suffocation due to being unable to exchange O2/CO2.

First, a "DO crash" kills fish...They suffocate and die.

Second, High levels of Hydrogen Sulfide gasses from decay are common in the summer months in a non-aerated pond below the thermocline. It is often referred to as "Anoxic" water. This build up is due to a lack of water circulation or mixing and has little to nothing to do with a "DO crash". In fact, the normal lack of oxygen in this layer of water is what causes the hydrogen sulfide to begin with.

Fish kills are somewhat common when you have a cold rain on warmer water that causes a sudden mixing of the upper and lower waters.

I guess I'm just trying to figure out what happened so I can prevent it from happening in the future. Right now I'm trying to figure out if it's safe to restock and the bigger question is what to restock and how much? The underwater camera only showed me perch and walleye, but when I fish the pond it's a dead sea. I'm curious wheter I lost all my fish. The pellet trained perch I put in aren't taking to my feeding yet I really want to keep an eye on them to see if they make it.

If you lost several fish, and it was recently, the fish are bound to be pretty stressed by whatever caused the kill. It will take some time for the fish to get back to normal.

At this point, I would just take a wait and see approach for the next couple weeks.