Document Type

Thesis

Degree Name

Master of Science (MSc)

Department

Biology

Program Name/Specialization

Integrative Biology

Faculty/School

Faculty of Science

First Advisor

Deborah MacLatchy

Advisor Role

Heidi Swanson

Second Advisor

Derek Gray

Abstract

Arctic grayling (Thymallus arcticus) are a cold-water salmonid that inhabit waterbodies throughout the circumpolar regions of the northern hemisphere. In the last decade, Ka'a'gee Tu First Nation members as well as local sport fishers, have observed lower catches of Arctic grayling during their annual spawning run in the Kakisa River, NWT. Many potential causes of this decline have been hypothesized including climate change and over harvesting. Outside of the general annual spawning activity in the headwaters of the Kakisa River, the ecology of the population, including post-spawn habitat use and migratory patterns, remained understudied. To address these knowledge gaps, acoustic transmitting tags were surgically implanted into 76 adult Arctic grayling in the spring of 2022. An acoustic receiver array of 27 receivers were deployed throughout the Kakisa River and Beaver Lake, a wide section of the Mackenzie River. In addition, three receivers deployed in southwest Great Slave Lake, part of the Department of Fisheries and Oceans’ (DFO) ongoing fisheries monitoring programs, were also incorporated into the study. Tagged adults were monitored between April 2022 and October 2023. The recovered array of eight receivers captured 10,015 detections of 65 grayling over the study period, providing new insight into the migration patterns, timing of seasonal movements and thermal habitats of adult Arctic grayling in the upper Mackenzie region. The telemetry data revealed new information previously undocumented about grayling movements in the watershed including the dates, water temperatures and ice conditions of entry and exit by grayling into the Kakisa River from Beaver Lake, as well as data on how long grayling remained in the Kakisa River post spawn. Prior to the study, relatively little was known about the migration destination of Kakisa River grayling. The telemetry study found that a number of iii individuals occupied Beaver Lake throughout the summer and fall presumably to carry out summer feeding activities post spawn. In addition, several individuals were found occupying and migrating through Beaver Lake during the winter. Individuals were also tracked migrating to Great Slave Lake, indicating that some grayling travel over 70 km from their natal spawning grounds to reach summer and overwintering habitats. The study provides new information on the post spawn migratory behaviour, particularly with respect to summer feeding and overwintering ecology. The information gathered as part of this study, along with future work on Arctic grayling in the upper Mackenzie River, will be important for predicting and managing the potential impacts of climate and other stressors on this ecologically, socially and culturally important fish species.

Convocation Year

2025

Convocation Season

Spring

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