Date of Award

5-16-2025

Publication Type

Thesis

Degree Name

M.Sc.

Department

Earth and Environmental Sciences

Keywords

Acoustic Telemetry; Centrarchidae; Climate Change; Inverse Stratification; Thermal Ecology; Winter Limnology

Supervisor

Aaron Fisk

Supervisor

Bailey McMeans

Rights

info:eu-repo/semantics/openAccess

Abstract

Under a changing global climate, north temperate lakes are experiencing warmer winter temperatures with receding ice duration. Yet, how warm-water fish inhabiting these ecosystems behaviourally respond to changing year-over-year winter conditions is unknown. Here, I employed acoustic telemetry to track the overwintering behaviours (daily temperature occupancy, depth, and activity, and winter home ranges) of 13 adult smallmouth bass (Micropterus dolomieu), a warm-water centrarchid, in a boreal lake (Smoke Lake, Algonquin Park, Ontario) across three consecutive winters (2021-22, 2022-23, 2023-24). Winter temperatures and smallmouth bass overwintering behaviours varied across the three years. Within-year variation across individuals was high, but the population migrated to deeper depths to maintain consistent experienced temperatures during years 1 and 2 (9.0 +/- 6.6 m and 14.9 +/- 6.9m, respectively, and 2.34 +/- 0.20˚C and 2.26 +/- 0.36˚C, respectively). However, the bass remained at shallower, colder depths in year 3 (7.8 +/- 5.0 m and 1.84 +/- 0.24˚C), the year with shortened ice duration, despite warmer temperatures being available deeper. Overwinter space use size was greatest in year 2, with significant variation observed among individuals. Finally, in the year spring warming began two weeks earlier, an increase in smallmouth bass activity coincided. My research provides evidence of a Centrarchidae species responding to changing thermal conditions in winter via behavioural traits, including what appears to be the first confirmation of flexible depth use beneath an ice-covered lake, which may play an important role in their responsiveness to climate warming.

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