13:45 〜 14:05
[AOS13-13] Biogeochemical fingerprints of ocean migration of Pacific salmon
★Invited Papers
キーワード：同位体地図、サケ、回遊経路、窒素安定同位体比
Long-distance ocean migration by marine fish has long fascinated scientists, and a better understanding of such migrations may hold important keys to understanding the impacts of ongoing climate change as well as the evolutionary history and mechanisms of niche partitioning in these taxa. However, research into this topic has been hampered by the substantial investment of time and effort required to monitor fishes in the ocean using field surveys.
The migration history of a fish can be recorded as isotope ratios in tissues such as the otolith and vertebral centrum that undergo incremental growth. Specifically, by combining data on spatial patterns in isotope ratios (isoscapes) with retrospective isotope analysis of vertebral centra, it is possible to reconstruct potential individual migration routes.
In this study, I revealed chum salmon migration routes using the isoscape and retrospective isotope analysis of the salmon. Initially, the isoscape of stable nitrogen isotope ratios (δ15N) at the base of the food web (δ15NBase) in the northern North Pacific was generated by conducting compound-specific isotope analysis of amino acids from copepods sampled across the region. Then, I performed retrospective stable nitrogen isotope analysis of mature chum salmon sampled from different streams in Japan. Finally, the migration routes of individual salmon were estimated by using a state-space model which can incorporate the isoscape and retrospective isotope shifts of salmon.
The isotope tracking successfully reproduced a known salmon migration route between the Okhotsk and Bering seas. In addition, the results suggested the presence of a new migration route to the continental shelf of the eastern Bering Sea during a later growth stage. The later stage of skeletal growth of salmon is corresponds to the timing of sexual maturation of this species. For this reason, this study strongly suggested that the Bering Sea Shelf is a destination of ocean migration of chum salmon, and the purpose of their journey should be fulfilling the nutritional demands of sexual maturation in this highly-productive region.
The results of this study suggested that Asian population of chum salmon strongly depend on the nutrient in the Bering Sea Shelf in the far distance from Japan. It anticipates that monitoring and management of the environment of their habitat while traveling in the ocean as well as their natal river and coastal area are important for sustainable use of salmon resources. The isoscape of stable nitrogen isotope ratios generated in this study can be applied for isotope tracking of various animals which migrate the North Pacific Ocean. Hence, the method of this study will strongly promote the future use of isoscape for migration study of marine animals.
The migration history of a fish can be recorded as isotope ratios in tissues such as the otolith and vertebral centrum that undergo incremental growth. Specifically, by combining data on spatial patterns in isotope ratios (isoscapes) with retrospective isotope analysis of vertebral centra, it is possible to reconstruct potential individual migration routes.
In this study, I revealed chum salmon migration routes using the isoscape and retrospective isotope analysis of the salmon. Initially, the isoscape of stable nitrogen isotope ratios (δ15N) at the base of the food web (δ15NBase) in the northern North Pacific was generated by conducting compound-specific isotope analysis of amino acids from copepods sampled across the region. Then, I performed retrospective stable nitrogen isotope analysis of mature chum salmon sampled from different streams in Japan. Finally, the migration routes of individual salmon were estimated by using a state-space model which can incorporate the isoscape and retrospective isotope shifts of salmon.
The isotope tracking successfully reproduced a known salmon migration route between the Okhotsk and Bering seas. In addition, the results suggested the presence of a new migration route to the continental shelf of the eastern Bering Sea during a later growth stage. The later stage of skeletal growth of salmon is corresponds to the timing of sexual maturation of this species. For this reason, this study strongly suggested that the Bering Sea Shelf is a destination of ocean migration of chum salmon, and the purpose of their journey should be fulfilling the nutritional demands of sexual maturation in this highly-productive region.
The results of this study suggested that Asian population of chum salmon strongly depend on the nutrient in the Bering Sea Shelf in the far distance from Japan. It anticipates that monitoring and management of the environment of their habitat while traveling in the ocean as well as their natal river and coastal area are important for sustainable use of salmon resources. The isoscape of stable nitrogen isotope ratios generated in this study can be applied for isotope tracking of various animals which migrate the North Pacific Ocean. Hence, the method of this study will strongly promote the future use of isoscape for migration study of marine animals.