I knew what to expect long before the ice began to melt from my small pond. Even though the pond is extremely deep for its surface area, the long accumulation of thick ice and deep, smothering snow this winter left little hope for the survival of the fish in the pond.
Sure enough… once the ice retreated, I saw several larger dead fish floating on the surface. At first, I thought maybe it wasn’t too bad. Then, I glanced down at the shallow water at the pond’s edge. There were hundreds of small fish corpses in various stages of decomposition. It didn’t take long to see, the fish kill was complete. All of the fish in the pond had died due to the thick ice and heavy snow shutting off the life-giving rays of the sun for the aquatic vegetation. Once the plant life died, it began to decompose and took all of the oxygen out of the water.
I had witnessed something similar three years ago. The ice and snow took most of the oxygen from the water and killed all of the large channel catfish in the pond. I had a lot of surviving fish… small bluegill, yellow belly catfish and crappie. This year though, even the smallest bluegill perished. It was a complete winter kill.
Indiana’s DNR had previously warned owners of shallow ponds and lakes to watch for fish kills this spring. Considering the record or near-record snowfall and ice up to 20 inches thick on lakes and ponds, Indiana fisheries biologists anticipated numerous reports of fish kills once bodies of water thaw.
The most common cause of fish kills in Indiana ponds is lack of oxygen. Aquatic plants can produce oxygen only when sunlight is available. While some sunlight can penetrate clear ice, snow can block sunlight, resulting in dangerously low oxygen levels.