Effect of lampricide exposure on olfaction and stress physiology in juvenile lake sturgeon (Acipenser fulvescens)

Abstract

Freshwater ecosystems are facing increasing pressures from invasive species, habitat alteration, and chemical pollutants. In the Laurentian Great Lakes, lampricides have been used for decades to suppress invasive sea lamprey, and the sea lamprey program is widely credited as a critical component of the recovery and maintenance of native fisheries. However, the application of these chemicals in nursery streams also creates potential risk for non-target species of conservation concern, such as lake sturgeon (Acipenser fulvescens), whose early life stages often overlap spatially and temporally with treatment zones. While young-of-the-year (YOY) sturgeon have been shown to exhibit functional impairments following lampricide exposure, the vulnerability of older juveniles remains unclear. To address this gap, I investigated whether short-term exposure to TFM or a TFM with 1% niclosamide mixture affects olfactory sensitivity or stress physiology in yearling (age 1+) lake sturgeon. I exposed fish for either 30 minutes or 12 hours and evaluated responses immediately after exposure and following a six-day recovery period. I measured plasma cortisol and glucose concentrations to evaluate baseline endocrine function, responsiveness to handling stress, and post exposure patterns over time. I used electro-olfactography to assess activation of microvillous and ciliated olfactory sensory neurons using L-alanine and taurocholic acid as stimuli. I found no treatment-related effects on baseline cortisol, cortisol responsiveness, circulating glucose, or stress-induced glucose, indicating that endocrine and energetic function remained intact under the exposure conditions used in this study. I also observed no reductions in EOG amplitudes, suggesting that peripheral olfactory sensitivity was not impaired. In contrast to YOY sturgeon, my results indicate that yearling lake sturgeon may have greater physiological tolerance to lampricide exposure, particularly under moderate alkalinity and near-neutral pH conditions. Overall, my research adds to a growing body of literature that collectively demonstrates that non-target vulnerability to lampricides is strongly influenced by life stage, physiological development, and environmental context, and contributes evidence that can improve life-stage-specific risk assessment and conservation planning for lake sturgeon.