Master of Science (MSc)
Faculty of Science
Dr. Michael P. Wilkie
The lampricide 3-trifluoromethyl-4-nitrophenol (TFM) is applied to tributaries of the Great Lakes to control invasive sea lampreys (Petromyzon marinus). Although TFM is selectively toxic to larval sea lampreys, non-target mortality can occur during lampricide treatments. It is important to know whether or not TFM played a role in the death of these fishes, and the most direct means to do this is using forensic science principles. The objectives of this study were to: (i) determine the acute toxicity of TFM to the non-target fishes, rainbow trout (Oncorhynchus mykiss) and white sucker (Catostomus commersonii), and how the lampricide is distributed in the blood, liver and white muscle of these fishes, (ii) establish concentrations in the blood and tissues that could cause death to non-target fishes, and (iii) ascertain the most appropriate methods of blood and tissue sample storage and preservation for the investigations of non-target mortality. TFM concentrations and relative amounts of TFM-metabolites were measured in the blood and tissues of the non-target fish using LC-MS/MS following exposure to their 9-h LC25 for 6 h. Data showed that rainbow trout had a 12-h LC50 of 13.3 mg l-1 compared to a value of 15.0 mg l-1 for white sucker and that TFM concentrations for both species were by far the greatest in the liver, which is well supplied with blood and also equipped with organic anion transporters which transport xenobiotics such as ionized TFM into hepatocytes. At lethal exposure concentrations, a “spill-over” effect was observed characterized by TFM concentrations that exceeded the detoxification capacity of the liver, leading to significantly increased concentrations in the blood and muscle, compared to those measured at sub-lethal exposure concentrations. The testing of various storage methods on the stability of TFM and its metabolites in blood and tissues showed that while liver accumulated the greatest amount of TFM, it was also prone to large changes in both parent TFM and its metabolites at sub-optimal storage conditions for lengths of time greater than 1 h. Concentrations of TFM were most stable in muscle, likely due to its relative lack of detoxification enzymes and isolation from the microbes of the gastrointestinal tract. The present study demonstrates that, if possible, liver, white muscle, and whole blood should be collected from non-target fishes following unexplained mortality and although quick freezing using liquid N2 or dry ice and longer-term storage at temperatures lower than -20˚C is optimal, keeping samples on ice or at room temperature for no longer than 1 h can yield lampricide measurements of reliable quality.
Foubister, Darren, "Distribution and Stability of the Lampricide 3-Trifluoromethyl-4-Nitrophenol (TFM) in Non-Target Rainbow Trout (Oncorhynchus mykiss) and White Sucker (Catostomus commersonii)" (2018). Theses and Dissertations (Comprehensive). 2051.