Notice of the Final Oral Examination for the Degree of Doctor of Philosophy
Topic
Using microchemistry to track the marine migrations of coho and Chinook salmon
Department of Biology
Date & location
- Tuesday, March 31, 2026
- 1:00 P.M.
- Clearihue Building, Room B007
Examining Committee
Supervisory Committee
- Dr. Francis Juanes, Department of Biology, 探花系列 (Supervisor)
- Dr. John Dower, Department of Biology, UVic (Member)
- Dr. Tanya Brown, Department of Biological Sciences, Simon Fraser University (Outside Member)
External Examiner
- Dr. Karin Limburg, Department of Environmental Biology, State University of New York College of Environmental Science and Forestry
Chair of Oral Examination
- Dr. Doug Magnuson, Department of Educational Psychology and Leadership Studies, UVic
Abstract
Pacific salmon (genus
Oncorhynchus) display complex life history strategies from estuary entry to their return migrations. During this marine migration and residency period, Pacific salmon can traverse thousands of kilometers, moving to and through multiple unique marine regions with their own unique set of environmental and ecological conditions that these fish must contend with to survive. The marine migration and residency period of Pacific salmon, is still poorly described, often considered a black box, despite 100 years of considerable international effort. Current methods using passive tags are often difficult to interpret through seasons and across patchy distributions and inconsistent fishery efforts. Active tags can provide more high scale resolution, though at a steeper cost and substantial tag burden effects for smaller salmon. Intrinsic tags, those aspects of the fish that are universally part of an organism’s biology, provide researchers with a novel method of tracking fish migrations. This dissertation reports on the results of using otoliths as intrinsic tags in both coho (O. kisutch) and Chinook salmon (O. tshawytscha). Chapter 1 acts as an introduction and a 100-year retrospective on Pacific salmon tagging ventures up to this point in time. Chapter 2 and 3 focus on using otolith microchemistry to identify the marine migrations of coho and Chinook respectively. Chapter 4 identifies growth considerations within coho salmon related to migration, with slower growing coho in the early marine period being more likely to partake in further migrations. Chapter 5 focuses on producing otolith size to fork length size to interpret early life stage events in Chinook and coho salmon, with some investigations into the estimation of the size at estuary entry and estuary residence time of Chinook salmon. Chapter 6 looks at ageing Chinook salmon through otolith microchemistry, with some key findings including that older Chinook are more likely to be underaged by scales, and that larger Chinook salmon at their first ocean winter return at a younger age and smaller size. Chapter 7 applies otolith microchemistry analyses to contaminants research, identifying that predicted otolith marine migration life-history types match general expectations for contaminant profiles of Chinook salmon that conduct migrations to both coastal and offshore environments. Finally, chapter 8 is a six-year retrospective on this type of research and some considerations for future international collaborations.
