Fish Kills Become Evident as Brutal Winter Ends

 

Snail Lake was hit hard this year by winter kill.

By Bill Bartodziej

Dead carp visible from the shore
of Gervais Mill Ponds in Little Canada.

We had a combination of factors come together this winter to result in low oxygen levels in our area lakes. Early ice formation was quickly covered by a hefty blanket of snow that finally started to melt in March. Ice sheets on our lakes basically form a barrier between water and air, and gas exchange becomes very limited. In addition, the thick layer of snow limits light that reaches plants in the lake water. Without much light, plants can’t photosynthesize and give off oxygen. As the winter wears on, oxygen is used up by a variety of animals in our lakes and levels can become critically low. Shallow lakes are more prone to this sort of natural disturbance.


Snail is one lake in our watershed where a fish kill has been reported. We suspect that other shallower lakes may also have experienced fish kills. We will have a better idea of the magnitude of the problem once the ice melts. Inevitably, a certain number of fish will float to the surface and wash up on shore.


TJ DeBates, the East Metro Fisheries Manager for DNR, plans on surveying area lakes that have been hit hard by winter kill. “We will use this data to better understand the impact on the game fish populations. Spring stocking will be ramped up to mitigate for the loss to our fisheries.”