Aqueous exposure to a pyrethroid pesticide results in behavioural effects in early life stage sturgeon

The presence of chemical contaminants in freshwater systems poses a threat to many aquatic organisms, and understanding the extent and nature of this threat can facilitate conservation management actions. Sturgeon are considered threatened worldwide and they differ in many important ways from other fishes. Two sturgeon species, green sturgeon (<i>Acipenser medirostris</i>) and white sturgeon (<i>A. transmontanus</i>), are found in California and utilize anthropogenically impacted freshwater habitats of the Central Valley. This study evaluated the behavioural effects in endogenously feeding larvae (3-7 days post hatch) of both sturgeon species following an acute exposure (96 hours) to the pyrethroid pesticide bifenthrin at aqueous concentrations ranging from 10 to 2000 ng/l, with selected levels based on previous environmental monitoring. Sturgeon had high survival at all concentrations tested (~95%), yet at higher concentrations (>1000 ng/l) they displayed altered behavioural patterns, including reduced activity, increased meander of the movement path and reduced thigmotaxis. While these higher concentrations of bifenthrin have been observed within water samples from the sturgeon habitats of California, they appear uncommon. The present study suggests that sturgeon larvae are not highly sensitive to acute aqueous exposure under environmentally relevant concentrations of bifenthrin (1-10 ng/l), yet these aqueous concentrations do have behavioural effects that may be of concern for the conservation of these declining species. Additionally, impacts to these species may also occur through exposure to sediment-bound bifenthrin or dietary bioaccumulation, and more work needs to be done to understand the implications of these exposure routes.