Current-use pesticides affect development of early life stages and timing of alevin emergence in Sockeye salmon (Oncorhynchus nerka)

The effects of two pesticides on Pacific sockeye salmon (Oncorhynchus nerka) exposed from fertilization to emergence were evaluated in a gravel-bed flume incubator, designed to simulate a natural streambed environment. Eggs were exposed to a commercial formulation of atrazine at 25 or 250 μg/L, and chlorothalonil at 0.5 or 5 μg/L, to examine effects on developmental success and timing, physical growth parameters, and biochemical indicators of growth. High chlorothalonil exposure reduced survival to hatch and increased finfold deformity incidence. All treatments resulted in reduced alevin condition factors at the time of emergence. Atrazine exposure resulted in premature hatch, while chlorothalonil exposure resulted in delayed hatch compared to controls. All treatment groups experienced premature emergence, highlighting the importance of using a gravel-bed incubator to examine this subtle but critical endpoint. These alterations in developmental success, timing and growth may alter survival of early life stages of sockeye salmon in the wild.