North Pacific Anadromous Fish Commission

Technical Report 23

Table of Contents

Development of the Approaches Using Otolith Carbon and Oxygen Isotopes to Reconstruct Metabolic Histories and Experienced Temperatures of Juvenile Chum Salmon

Authors:
Yuxiao Gou, Takaaki K. Abe, Takatoshi Higuchi, Shiono Miki, Ryuji Hattori, Kentaro Honda, Kotaro Shirai, and Takashi Kitagawa

Abstract Excerpt:
To better understand the intrinsic and extrinsic factors that contribute to the high mortality of juvenile chum salmon Oncorhynchus keta during primary ocean migration, this study developed approaches using otolith carbon and oxygen isotopes to reconstruct their metabolic histories and experienced temperatures. Given that carbon in the otolith aragonite calcium carbonate is composed of metabolically derived carbon released from food respiration and dissolved inorganic carbon (DIC) in ambient water, and that the carbon in fish blood physiologically regulate blood pH to an optimum state, the relative contribution of metabolically derived carbon in otoliths can therefore reflect fish metabolic rates, relating to their physiological conditions. Since the metabolism-derived carbon is isotopically distinct from DIC (> 15‰ lower than DIC; Solomon et al. 2006), otolith carbon isotopes (δ13Cotolith) theoretically vary with fish metabolic activities and have been shown to be a useful metabolic indicator (Chung et al. 2019; Martino et al. 2020). Oxygen isotopes in otoliths (δ18Ootolith) are believed to be precipitated in or near isotopic equilibrium, and the precipitation process is primarily influenced by temperature (Morrissett et al. 2023). The species-specific fractionation of δ18Ootolith with temperatures has also been determined in chum salmon (Gou et al. 2022), thus δ18Ootolith is available to reliably reconstruct the experienced temperatures of juvenile chum salmon during primary migration.

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DOI:
https://doi.org/10.23849/npafctr23/21e-pji

Citation

Gou, Y., T.K. Abe, T. Higuchi, S. Miki, R. Hattori, K. Honda, K. Shirai, and T. Kitagawa.  2024.  Development of the approaches using otolith carbon and oxygen isotopes to reconstruct metabolic histories and experienced temperatures of juvenile chum salmon.  N. Pac. Anadr. Fish Comm. Tech. Rep. 23: 68–71.  https://doi.org/10.23849/npafctr23/21e-pji