Document Type

Thesis

Degree Name

Master of Science (MSc)

Department

Biology

Program Name/Specialization

Integrative Biology

Faculty/School

Faculty of Science

First Advisor

Dr. Michael P. Wilkie

Advisor Role

Supervisor

Abstract

The lampricide, 3-trifluoromethyl-4-nitrophenol (TFM), has been used to successfully control invasive sea lamprey (Petromyzon marinus) in the Laurentian Great Lakes for over 50 years. TFM’s effectiveness is due to the relatively low capacity of sea lamprey to detoxify TFM. Water temperature has been shown to increase TFM tolerance in larval sea lamprey. However, the effects of temperature on TFM sensitivity in non-target species such as the endangered lake sturgeon (Acipenser fulvescens) are poorly understood, particularly during their early life stages. To determine how temperature affected TFM sensitivity, age 1-year-plus (1+) lake sturgeon acclimated to 8, 16, or 20℃ were exposed to a field-relevant concentration of TFM (4 mg L-1). Survivorship was then monitored over 12 h and found to be lowest at 16℃ compared to cooler (8℃) and warmer (20℃) waters. Fish acclimated to 8°C and 20° accumulated less TFM than those at 16℃. Subsequent exposure to a sub-lethal TFM concentration (1 mg L-1) at each temperature was conducted to compare the effects of TFM accumulation and mRNA abundance of heat shock proteins (hsps) and biotransformation enzymes, including UDP glucuronosyltransferases (ugts) and sulfotransferases (sults). Sturgeon acclimated to 20℃ had significantly lower TFM accumulation in the muscle, suggesting more efficient TFM elimination. Fish acclimated to lower temperatures had greater mRNA abundance of inducible hsps, biotransformation, and oxidative stress enzymes than those at 16 and 20℃, while lake sturgeon at 16 and 20℃ had comparable mRNA abundance. In conclusion, TFM tolerance in lake sturgeon varies with temperature in a bimodal fashion, where tolerance is greatest at 8°C, decreases as temperatures rise to the mid-teens, and increases approaching 20°C. Thus, delaying lampricide treatments until late August or early September when fish are larger and have greater capacity to detoxify TFM would mitigate lake sturgeon mortality.

Convocation Year

2025

Convocation Season

Spring

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