Environment Canada is investigating three P.E.I rivers affected by major fish kill last month.
Traces of pesticide were discovered in the bottom sediment in the Big Pierre Jacques River and the Mill and Trout River in West Prince.
Last Friday preliminary results were released after tests were conducted to determine what had killed thousands of fish a couple of weeks earlier.
The results of the fish tissue have not yet come back.
If it's determined that the pesticide run-off killed the fish, Island Environmental groups and sport fisherman say they want tougher fines and bigger buffer zones.
