Dietary Exposure to Bifenthrin and Fipronil Impacts Swimming Performance in Juvenile Chinook Salmon (Oncorhynchus tshawytscha)

Two commonly used insecticides, bifenthrin and fipronil, can accumulate in the prey of juvenile Chinook salmon, yet the efl'ects of dietary exposure are not understood. Therefore, to better characterize the efl'ect of a dietary exposure route, juvenile Chinook salmon were fed chironomids dosed with a concentration of 9 or 900 ng/g of bifenthrin, fipronil, or their mixture for 25 days at concentrations previously measured in field-collected samples. Chinook were assessed for maximum swimming performance (U-max) using a short-duration constant accel-eration test and biochemical responses related to energetic processes (glucose levels) and liver health (aspartate aminotransferase (AST) activity). Chinook exposed to bifenthrin and bifenthrin and fipronil mixtures had a significa n t l y reduced swimming performance, although not when exposed to fipronil alone. The AST activity was significa n t l y increased in bifenthrin and mixture treatments and glucose levels were increased in Chinook following a mixture treatment, although not when exposed to fipronil alone. These findings suggest that there are difl'erent metabolic processes between bifenthrin and fipronil following dietary uptake that may influence toxicity. The significant reductions in swimming performance and increased levels of biochemical processes involved in energetics and fish heath could have implications for foraging activity and predator avoidance in wild fish at sensitive life stages.

Automated summary

This study investigated the effects of dietary exposure to bifenthrin and fipronil on the swimming performance, energetic processes, and liver health of juvenile Chinook salmon. The results showed that the ingestion of bifenthrin and the mixture of bifenthrin and fipronil significantly reduced swimming performance and affected certain biochemical indicators, while the ingestion of fipronil alone did not have a significant effect.