ELMIRA, N.Y. (WETM) – This winter across the Twin Tiers we saw temperatures below freezing long enough to cover local ponds with a thick coating of ice. On top of the cold temperatures we also had an extended period of time where we had feet of snow on the ground and ice covered ponds. This snow stayed on top of this ice for weeks. When this ice melted in late March, some ponds saw hundreds of dead fish floating at the top of them. This phenomenon is known as winter kill. But why does this happen and why does this happen in some ponds and not others?

Winter kill occurs when fish are deprived of their oxygen in the water that they use to live on. When the water is ice covered there is only so much oxygen in the water that remains that the fish are able to use. Usually they are able to survive because the ice thaws before the oxygen is depleted. Another way for the oxygen in the water to be replenished is by having plants at the bottom of the ponds and lakes. When there are many plants, sunlight that penetrates the ice can keep the photosynthesis process in the plants going. However, some winters snow pack over the ice is so dense that no sunlight can penetrate such as this past winter. This is why the fish died in some lakes this year. The plants at the bottom of the lake could not replenish the oxygen in the water to keep the fish alive thanks to the heavy snow and ice pack on these ponds.