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Lerner, Jacob

University of British Columbia

Chinook salmon (Oncorhynchus tshawytscha) are the largest, fattiest, and most diverse species of Pacific salmon and hold immense cultural, economic, and ecological significance. This is especially true in British Columbia (BC), Canada, where they support Indigenous communities, recreational and commercial fisheries, and endangered resident killer whale populations. Chinook spend the majority of their life in the ocean, where 99% of their growth and lipid accumulation occurs. Despite this, in BC, there are many open questions regarding their population-specific marine ecology, such as how much lipid they accumulate, their patterns of marine distribution, and, subsequently, what food webs they encounter and their role in these systems. This dissertation aims to address these questions, first by resolving differences in lipid content among ecologically significant populations of Chinook and then by using stable isotopes analysis of carbon (δ¹³C), and nitrogen (δ¹⁵N) to better understand their population-specific distribution, marine food webs, and trophic ecology. To do this, first, I calibrated a microwave fat meter to accurately measure whole body lipid content of Chinook salmon and then measured population-specific lipid content for Chinook from the Fraser River. In doing so, I demonstrated population-specific levels and seasonal differences in a trait crucial to successful Chinook spawning and valuable to endangered killer whales. Next, through experimental analysis I determined Chinook-specific verification of the assumptions underpinning the application of stable isotope analysis—lipid correction equations and trophic enrichment factors. With these established, I used stable isotopes infer population-specific differences in Chinook distribution and isotopic niche, complementing existing population distributions. Following this, I investigated regional food web structure in these marine foraging grounds, delineating the trophic relationships of the fish species constituting each food web and showing how food chain length varies with increases in primary production in eutrophic coastal ecosystems. Finally, I resolved population-specific regional trophic ecology using bulk and compound-specific SIA, illustrating the relationship between distribution, food webs, and Chinook foraging ecology. This dissertation provides novel analysis and interpretation of population-specific Chinook lipid content, marine ecology, and food webs, with important applications to the management of Chinook in BC and our understanding of the species’ life history.

Text

2024-02-29

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/87485

Oceanography

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/