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

Professor/Graduate Co-ordinator

Abstract

Invasive sea lamprey (Petromyzon marinus) contributed to massive declines in fisheries in the Laurentian Great Lakes due to their parasitism of large-bodied salmonid fishes in the 20th century. Chemical control measures, which involve the application of 3-trifluoromethyl-4-nitrophenol (TFM) into rivers containing larval sea lamprey, were successfully implemented approximately 60 years ago to control populations. Recently, however, it was discovered that TFM tolerance increases in sea lamprey with a rise in temperature for reasons which are incompletely understood. Nor is it understood how sea lamprey will respond to warmer temperatures due to climate change, which could affect their distribution in the Great Lakes. Warming waters could also jeopardize lake sturgeon (Acipenser fulvescens) conservation efforts by compromising their physiological capacity to forage, reproduce and evade predators. The goal of this thesis was to:

(i) Determine how the physiological performance of larval and juvenile sea lamprey is affected by warmer temperatures, and how it could influence their distribution in the Great Lakes.

(ii) Ascertain how warmer temperatures affect the physiological performance capacity of juvenile (young of the year; YOY) lake sturgeon in comparison to larval sea lamprey, which occupy similar habitat in the sturgeon’s early life stages.

To determine how warmer waters affected physiological performance, intermittent closed system respirometry was used to construct thermal performance curves in which O2 consumption (ṀO2) measurements were used to calculate standard metabolic rate (SMR) and maximum metabolic rate (MMR) of larval and juvenile sea lamprey, and YOY lake sturgeon, over a range of water temperatures. Aerobic metabolic scope (AMS = MMR – SMR) was then calculated at each temperature tested and used to calculate the thermal optima (Topt) and thermal breadth (Tbr) of the animals. The Topt of larval sea lamprey were 24.6, 25.4 and 26.2°C at acclimation temperatures of 6, 13 and 21°C, with a wide Tbr of 11.9°C (16.9-28.8°C), 10.9°C (18.5-29.4°C) and 10.9°C (19.8-30.7°C). Maximal AMS was highest in larvae acclimated to 13ºC, averaging 11.2 umol O2 g-1 h-1, and lowest at 8.1 umol O2 g-1 h-1 at an acclimation temperature of 21ºC. The Topt could not be calculated for juvenile sea lamprey because their maximal AMS (14.3 umol O2 g-1 h-1) was observed at the highest temperature tested (25°C), suggesting a surprisingly high thermal tolerance. Lake sturgeon were slightly less thermally robust, with a Topt of 22.8°C, but a higher maximal AMS of 14.8 umol O2 g-1 h-1, and Tbr of 11.7°C (range = 15.8 - 27.5°C). In conclusion, the relatively high Topt and wide Tbr of sea lamprey could have been a key adaptation the enabled them to successfully invade and occupy the Great Lakes. However, projected warming of rivers and streams could now result in reduced larval sea lamprey populations in some regions of the Great Lakes where water temperatures are already near their Topt. Conversely, lake-dwelling juvenile sea lamprey populations may benefit from warmer lake temperatures, which could promote growth and increased time to feed. Lake sturgeon populations could also be threatened by warming rivers as water temperatures approach or exceed their Topt, consequentially forcing them to migrate to less optimal habitats where food resources and protection from predators could be limited. The potential need to use higher amounts of lampricide in warmer waters to control sea lamprey, and the possible effects on lake sturgeon requires further investigation.

Convocation Year

2024

Convocation Season

Spring

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Available for download on Wednesday, January 29, 2025

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