I know of this small pond, approx 1 1/2 acre that was great to fish. It does have some geese with a lot of poop around but it has for years. A person that was removing old clay tile sewer lines and replacing with plastic threw the clay tiles in the pond instead of disposing of them proper. About a week or so later the crappie were floating on the top, over 400 I am told. My question is, is this coincidence or is it possible the old sewer lines could kill the fish?

Might be coincidental. Crappie fish kills are not uncommon

Algae bloom would be a possibility. Or pond turnover.

Lots of goose poop usually also means lots of nutrients which also means lots of weeds in the pond. Are there lots of weeds and if so, have you had many cloudy days leading up to the event? High weed concentrations often result in fish kills after several days of lower light due to less oxygen being produced while the fish are still using oxygen at the same rate. Of course the plants use oxygen as well.

I'd say the tiles upset the PH balance just enough to take the fish out, other wise you would have seen most everything dead, and you might yet !

If clay tiles are the result of fish kills we would have thousands of miles of rivers, streams and lakes with few to no fish.
There are viruses etc. that can multiply in certain environments. I have seen large flowages with huge kills caused by rapidly warming water in the spring but that may not be the case here. Also a small pond with not a lot of inflow and small water amount is not able to disperse or dilute organisms or bacteria etc. as well either.

Bryce

It's not the clay I was referring to, to change the PH, but the material on them, it can change the PH only a matter of tenth's of a percent to make a large kill. especially in a small area pond with not a lot of aeration to help it !

This is what I was thinking but I don't know enough about it. There's more dead fish.

good. it is very, very difficult to manage healthy crappie in a small pond. best thing for pond is likely a crappie die off. most are small and stunted. I would not be concerned with clay tiles unless they used to be a rotenone pipeline

Might have had clean out chemicals in side, ie: Draino, Liquid Plumber etc.

This would be my guess...it’s a little early in the year for a pond to be turning over. That usually happens in dog days, but an algae bloom would be very likely. We had one completely wipe out one of our creeks here.

I've seen early pond turnovers this time of year, though mostly due to human error.

This time of year (spring, when they are stressed and spawning) it is very common to see Bluegill and Crappies die due to Columnaris.

It is a bacterial infection, and you will see dead fish, and often fish swimming on their sides in shallower water too. Google it and you should see pictures of the infection on their sides and in their gills.

It is especially bad when bigger rains are followed by hot weather in the spring.

We had some winter kill here locally.

I saw some old tiles one time that were full of a whitish material that I was told was "phosphates" from laundry detergent. I have no idea of the validity of that analysis; just thought I'd mention it.

Thats probably true. Detergents in the old days had phosphates, thats why people had a harder time getting things clean for a while when formulations switched to phosphorous free