[A-OS13] Marine ecosystems and biogeochemical cycles: theory, observation and modeling

[AOS13-P09] Marine-Life-Tag: a way forward

*Shin-ichi Ito¹, Kotaro Shirai¹, Kazuki Yokouchi³, Toyoho Ishimura², Kagari Aoki¹ (1.Atmosphere and Ocean Research Institute, The University of Tokyo, 2.Graduate School of Human and Environmental Studies, Kyoto University, 3.Japan Fisheries Research and Education Agency)

Keywords:natural tag, stable isotopes, fish migration

The ocean, which covers 70% of the earth's surface, is home to numerous organisms, but due to its vast area, the life histories of many marine organisms remain largely unknown. Although the migratory pathways of target species have been estimated based on seasonal shift of fishing grounds, there are few examples of direct verification of the migration routes. In recent years, it has become possible to attach small GPS or light sensor to estimate the position of the target species with environments. However, there is no method to directly observe the migration of small marine organisms, especially during the juvenile stage when they are vulnerable to predation in nature and directly linked to changes in abundance.
The lack of information on migration pathways throughout the entire life history of marine organisms has prevented us from studying the environmental changes they experience during each life history stage. Whereas limited dietary information is available from stomach content, we have not been able to elucidate their life history strategies because we do not know their migratory routes and dietary change on the route. Therefore, a scientific question is still underdetermined: "What are the indicators of migration for each marine organism?”.
“Marin-Life-Tag” project was launched in 2022 to elucidate migration route and ontogenetic dietary change of marine organism using biogeochemical information stored in the organism body including tissue, vertebrae, otolith, scale and eye. The time resolution of vertebrae is limited by annual rings, whereas that of otolith is daily. Marine-Life-Tag project is targeting to develop methods to combine the biogeochemical information from multiple parts of the target species and couple to a growth-migration model to accurately determine the migration pathways of fish throughout their entire life history.