March 30, 2005

Advisory Concerning Increased Potential for Winter Fish Kills

Owners of shallow ponds are advised that the extensive snow and ice cover experienced this past winter greatly increases the threat of early spring fish kills in these water bodies. According to the Department of Environmental Protection’s (DEP) Inland Fisheries Division, conditions this past winter were very similar to those experienced two years ago, when DEP received numerous calls from Connecticut pond owners reporting dead fish in their ponds after ice out.

"Winterkills occur most frequently in very shallow, nutrient-enriched ponds that are subject to abundant growth of aquatic weeds," said Bill Hyatt, Director of DEP’s Inland Fisheries Division. "Conditions conducive to winterkill arise when heavy snow cover over ice inhibits sunlight penetration, thereby preventing aquatic plants from producing oxygen via photosynthesis. This process is the sole means of oxygen creation under ice-covered ponds. The greater the load of dead and decaying plant material, the more rapid the loss of oxygen and the more quickly fish can be stressed or killed by low dissolved oxygen levels. The fish typically die during the winter and are only observed following ice-out."

Winterkill is a natural event that varies from year to year depending on conditions. The extended period of snow cover atop frozen shallow lakes and ponds this past winter is expected to result in increased reporting of winterkill over the next few weeks. Pond owners who have experienced winterkill are advised that in the future, shoveling off some of the snow cover to allow light penetration can stave off potential winterkill conditions.

Pond owners who may observe abnormally high fish mortalities after ice out this spring can notify the DEP Inland Fisheries Division at the Headquarters in Hartford at (860) 424-FISH, the Eastern District Office in Marlborough at (860) 295-9523, or the Western District office in Harwinton at (860)-485-0226. The public is also advised that any fish kills observed in rivers, lakes, ponds, and streams any time of year can be reported to the Inland Fisheries Division at the numbers listed above. Biologists will discuss the caller’s observations and determine if a field investigation and involvement of other DEP units is needed. While most fish kills are natural occurrences, some have been attributed to human actions such as accidental or unauthorized releases of chemical toxins. Anyone reporting fish kills is asked to provide as much detail as possible concerning location, time and date, estimated size and numbers of fish involved, and other relevant site-specific information.

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