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

[AOS13-P09] Estimating some aspects of the biology of Sardinella lemuru recently recorded in the waters off Japan

*Alexanra Bagarinao Regalado^1,2、Shin-ichi Ito^1,2 (1.Atmosphere and Ocean Research Institute, The University of Tokyo、2.Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo)

キーワード：Otolith, Sardines, Age and growth, Reproductive biology, Indo-West Pacific

The genus Sardinella is abundantly distributed throughout the tropical and subtropical Indo-West Pacific (IWP) region, where they contribute economically and ecologically. Among the Sardinella species, the Bali sardinella, Sardinella lemuru, is one of the most abundant and heavily exploited in the area. The Bali sardinella was recently recorded in Japanese waters where information on some aspects of its biology is still lacking. This study provides initial estimates of age, growth, and reproductive characteristics of S. lemuru. Specimens were collected from Kanagawa and Kagoshima prefecture by commercial fisheries in July 2023 with size ranging from 16.4 to 22.4 cm SL. The estimated age range based on daily otolith increments is 371 – 435 d with hatch months corresponding from May to July 2022. Wide increment widths were observed at day 40 – 80, which could indicate faster growth during the early life stage. Almost all the individuals caught are mature or at the spawning stage, with gonado-somatic index (GSI) ranging from 1.9 to 7.9, indicating that reproduction is occurring in the waters off Japan. Estimated total fecundity for individuals with size range 17.4 – 18.4 cm SL range from 28,080 to 32,954. However, it is not clear whether they can close their life cycle in the waters off Japan or not. Otolith microchemistry analysis is expected as a future study to investigate their origin.