Application of geochemical markers to fisheries ecology

Megan Katherine Nims

doi:10.7273/000005099

A thorough comprehension of the life history traits of fish populations is necessary for the effective conservation and management of fisheries resources. Fisheries geochemistry is an interdisciplinary approach that merges ecology, chemistry, and geology to provide answers to various life history questions. The overall objective of this dissertation is to enhance the utility of fisheries geochemistry to gain deeper insights into the life history of fish, particularly with regards to the challenges posted by global climate change. The work presented here focuses specifically on the development of geochemical markers to investigate temperature, metabolism, and origin in Pacific salmon. First, Chapter 2 presents a review of methods used for the analysis of calcified fish structures, including a discussion of analytical techniques, their strengths and limitations, avenues for future development, and reporting requirements. Second, Chapter 3 investigates the temperature-dependent fractionation of otolith oxygen isotopes in juvenile Chinook salmon (Oncorhynchus tshawytscha), introducing a species-specific fractionation equation that can be used to retrospectively determine temperature that fish were exposed to. Third, Chapter 4 explores the use of otolith carbon isotopes in juvenile Chinook salmon as a proxy for metabolism. This study resulted in a quantification of the relationship between the proportion of metabolic carbon in the otolith and specific respiration rate (as a measure of metabolism), which can be applied to wild Chinook salmon to examine individual and population specific differences in metabolism. Fourth, Chapter 5 uses strontium isotopes to determine if adult pink salmon (O. gorbuscha) captured in the Arctic are locally produced. This study indicated that while most fish did not originate in the region, Arctic origin could not be ruled out for a small but notable proportion of fish. Taken together, the information presented in this dissertation enhances the utility of fisheries geochemistry as a tool to investigate trends in temperature, metabolism, and habitat use patterns, particularly as they relate to long-term shifts driven by global climate change. The information presented here can be applied in future studies to uncover crucial insights into fish life history and how life history traits can significantly shift in response to perturbations in climate.

Application of geochemical markers to fisheries ecology

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