DEVELOPMENT OF A RESPONSE SPECTRUM MODEL FOR BIFENTHRIN USING JUVENILE CHINOOK SALMON (ONCORHYNCHUS TSHAWYTSCHA)

Author

Katie Jo Knaub, Southern Illinois University CarbondaleFollow

Date of Award

8-1-2024

Degree Name

Master of Science

Department

Zoology

First Advisor

Lydy, Michael

Abstract

Long-term declines in salmonid populations observed in California Central Valley have prompted efforts to enhance the understanding of how environmental stressors impact sensitive species. Bifenthrin, a current-use insecticide, has been consistently detected throughout the Sacramento-San Joaquin River Delta (Delta) and has been linked to detrimental effects in salmon. Traditionally, aqueous concentration is used in toxicological studies to evaluate the effects of pesticides on aquatic organisms, which assumes that concentration of the toxicant in water is a valid surrogate for dose. The critical body residue approach was established as an improved technique for assessing toxicity of hydrophobic contaminants, but there is a lack of data to support the application of this method in assessing risk of contaminant exposure in the environment. The current study creates a response spectrum model (RSM) demonstrating the relationship between internal residue and effects observed in Chinook Salmon from laboratory-based exposures. To develop the RSM, a series of behavioral and physiological endpoints were measured using bifenthrin-dosed Chinook Salmon to use with previously generated mortality data for incorporation in the model. The most sensitive endpoints were locomotion and shoaling behavior, followed by anxiety, growth, swim performance, upper thermal sensitivity, olfactory response, and lethality. The RSM endpoints were compared to bifenthrin residues in field-collected juvenile Chinook Salmon collected in 2019-2020 as part of our earlier studies. We found bifenthrin tissue residues were at similar levels to the most sensitive endpoints featured in the RSM, suggesting that bifenthrin exposure in the field is likely to cause behavioral effects to salmon as they out-migrate through the Delta. The developed RSM is a tool that could be used by water quality managers to evaluate the extent to which bifenthrin exposure may impact behavior and performance in juvenile salmon, providing a field-based verification of its effects on outmigration.