This season’s cold and record snowfall make it hard for
wildlife, but for fish, mussels, plants and other aquatic life, but
on some water bodies a severe winter can be fatal. As ponds and
lakes freeze over and snowfall piles up on the ice, the fish and
their fates are sealed, literally, under a layer of ice. Winter
fish kills (or winterkill) are the result of significant decline in
oxygen levels in a water body during a long period of ice and snow
cover. Snow-covered ice blocks sunlight, greatly decreasing the
amount of oxygen plants and algae once produced. Oxygen levels drop
further because all aquatic life, including the fish, are consuming
what little oxygen is left in the water. In these conditions, a
complete winterkill can occur. This condition is natural and rarely
the result of pollution such as illegal dumping, sewage or a
Reports of strong “rotten egg” odors are generally the first
clue that a waterbody is experiencing anoxia (lack of oxygen). The
odor is hydrogen sulfide gas which is a natural by-product
occurring in lakes and ponds with low amounts of dissolved oxygen.
Ice anglers are often the first to notice these conditions and
observe distressed fish gasping for air at holes in the ice or live
baitfish dying on fishing lines. The Division of Fisheries and
Wildlife (DFW) has recently received several calls from ice
fishermen reporting this phenomenon on some shallow, weed-choked
lakes. DFW fisheries biologists routinely find low dissolved oxygen
levels in these types of habitats; prime candidates for winterkill.
Most of the time, the results of winterkill are not seen until
spring when the ice melts and citizens discover dead fish on the
bottom of the pond or floating at the surface.
To report a fish kill Monday through Friday between 8:00 am and
4:30 PM, contact Richard Hartley at (508) 389-6330. After normal
business hours or on holidays and weekends, contact the
Environmental Police Radio Room at (800)-632-8075.