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

Abstract

Two commonly used insecticides, bifenthrin and fipronil, can accumulate in the prey of juvenile Chinook salmon, yet the effects of dietary exposure are not understood. Therefore, to better characterize the effect 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 acceleration 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 significantly reduced swimming performance, although not when exposed to fipronil alone. The AST activity was significantly 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 different 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.

Bifenthrin, a Ubiquitous Contaminant, Impairs the Development and Behavior of the Threatened Longfin Smelt during Early Life Stages

“…64−65 This is supported by a recent study that showed reduced swimming performance in Chinook Salmon (Oncorhynchus tshawytscha) juveniles following dietary exposure to bifenthrin. 16 Although no cardiotoxic effect was observed in this study, bifenthrin induced contrasting changes in Longfin Smelt behavior, depending on the duration of the exposure and the life stage exposed. Individuals exposed during the larval stage displayed a strong pattern of hypoactivity when tested after 48 h, but this behavioral change faded when measured at 72 and 96 h. On the other hand, individuals exposed throughout their embryonic development displayed an increased pattern of activity when tested at 1 dph.…”

“…Although the bifenthrin effect on fish cardiac thermal tolerance was not tested before, DeCourten et al (2020) reported cardiac deformities in Inland Silversides (Menidia beryllina) exposed as larvae to an environmentally relevant concentration (5 ng/L). Other studies using acute concentrations (ranging from 256 μg/L to 12.7 mg/L) found abnormal cardiovascular development and reduced heart rate in developing Zebra Danio. , Theoretically, such cardiac defects can lead to reduced cardiac output, which is a major driver of fish upper thermal limits and swimming performance. − This is supported by a recent study that showed reduced swimming performance in Chinook Salmon (Oncorhynchus tshawytscha) juveniles following dietary exposure to bifenthrin …”

“…For the past few decades, synthetic pyrethroids have been used as one of the leading global insecticides, replacing restricted or banned insecticides, such as organophosphates. , The resulting widespread use of pyrethroids in urban and agricultural areas is associated with runoff, leaching, and spray drift, which are routes of unintended contamination of pesticides in receiving water bodies. , Thus, pyrethroids are ubiquitous in many aquatic environments, where they threaten biodiversity. ,, Pyrethroid pesticides have been reported to cause nontarget toxicity in aquatic organisms, especially in fish. The primary mechanism of action of pyrethroids, paralysis via sodium channel disruption, has been reported to cause a broad range of sublethal effects in fish, including reduced sperm motility and resulting poor fertilization success, , cardiotoxicity, reduced swimming performance, , and behavioral alteration. , …”

“…8,10,11 Pyrethroid pesticides have been reported to cause nontarget toxicity in aquatic organisms, especially in fish. The primary mechanism of action of pyrethroids, paralysis via sodium channel disruption, has been reported to cause a broad range of sublethal effects in fish, including reduced sperm motility and resulting poor fertilization success, 12,13 cardiotoxicity, 14 reduced swimming performance, 15,16 and behavioral alteration. 17,18 Bifenthrin is one of the primary pyrethroid insecticides used in California's urban and agricultural applications.…”

The Use of Non-targeted Lipidomics and Histopathology to Characterize the Neurotoxicity of Bifenthrin to Juvenile Rainbow Trout (Oncorhynchus mykiss)

“…The predominant focus of the integrated overlay of previously conducted metabolomic and transcriptomic studies with lipidomics was based on a single family of fish, salmonids, as a great amount of data is required that has similar exposure profiles to limit the influence of additional variables that may impact bifenthrin toxicity. However, alternative exposure routes should be considered in future studies, as well as other threatened and endangered fish in the Delta, as pesticide-laden diets have recently been reported to impair swimming performance in inland silversides and Chinook salmon, − with predominate targets involved in upstream lipid metabolism and energetic pathways. The framework of comparing multiple omic profiles to understand the underlying mechanistic effects of contaminants, while considering subsequent species and pesticide exposure routes, is warranted and will allow for more informative decisions to be made and results implemented in future risk assessments.…”