The Department of Environmental Resources reports that analyses completed on samples collected from Profit's Pond found the pesticide chlorothalonil at low levels in water and sediment. Water, sediment and fish samples were collected from the Profit's Pond area on July 20, the same day that a fish kill was observed in the pond. Water and sediment were analysed for a selection of pesticides including those used in the watershed in the days prior to the fish kill. Chlorothalonil was the only pesticide detected in these samples. It was found at a concentration below that normally toxic to fish. The concentration was above the Canadian Council of Ministers of Environment water quality guideline for freshwater aquatic life in general. While dissolved oxygen and temperature were at normal levels in the pond, silt concentrations were elevated.
Chlorothalonil is an active ingredient in the product Bravo, a common agricultural fungicide. Interviews of farmers, conducted by pesticide inspectors for the Department of Agriculture, Fisheries and Forestry determined that Bravo was applied to a number of fields in the watershed of the pond prior to the fish kill. No evidence of improper usage or application was found during their investigation.
While the pesticide was detected at a low level in the water and sediment samples tested from the pond, concentrations may have been higher prior to the sample collection. Preliminary findings from fish autopsies found that the fish may have been exposed to a toxic chemical but were otherwise healthy. Further tests are planned on fish but due to the rapid breakdown of chlorothalonil by the fish, the tests may not be conclusive. More water and sediment tests are being conducted for chlorothalonil and another pesticide to further refine understanding of the fish kill.
At this time, due to the low levels of pesticide detected and the potential for impact from other factors such as silt, the Department of Environmental Resources is unable to conclusively say what killed the fish at Profit's Pond. Remaining tests to be completed in water and sediment are expected in a couple of weeks. Remaining tests for fish may be weeks before being complete.