[A-OS15] Marine ecosystems and biogeochemical cycles: theory, observation and modeling

[AOS15-P05] Contrasting life-history traits in Sardinella lemuru populations in the western Pacific

*Alexanra Bagarinao Regalado^1,2,4、Kaito Inoue³、Wilfredo Campos⁴、Shin-ichi Ito² (1.Department of Aquatic Bioscience, Graduate School of Agriculture and Life Sciences, The University of Tokyo、2.Atmosphere and Ocean Research Institute, The University of Tokyo、3.Miyazaki Prefectural Fisheries Research Institute、4.OceanBio Lab, Division of Biological Sciences, CAS, University of the Philippines)

キーワード：Bali sardinella, life-history traits, otolith microstructure, reproductive traits, contrasting environments

The Bali sardinella, Sardinella lemuru, is one of the most abundant sardine species in the tropical western Pacific. In the recent years however, it has been observed to expand its distribution range in the temperate waters off Japan. In this study, a comparison of life-history traits of S. lemuru populations occurring in the tropical and temperate waters of the western Pacific was carried out based on otolith microstructure and reproductive traits analyses. Tropical sardines are characterized by small to medium size (~17 cm SL), faster early life growth (0.5–1.3 mm d^-1), younger(smaller) age(size)-at-maturity (< 1 year), longer spawning duration (6 – 9 mos.), lower fecundity (mean: 20,858) with small to medium size eggs (mean: 303 µm). On the other hand, temperate sardines display contrasting life history traits, with larger size (~23 cm SL), slower early life growth (0.25–0.6 mm d^-1), mature older (> 1 year) and at a larger size (< 16 cm SL), higher fecundity (mean: 50,971) and bigger eggs (mean: 533 µm). Comparison of egg quality indicates that energy allocation also appears to differ with temperate sardines investing more on growth while tropical sardines invest their energy on reproduction. These results are consistent with the temperature-size rule (TSR) and further showed that sardines occupied varying position on the r and K continuum. The expansion in the distribution range of S. lemuru allowed us to examine how populations respond to environmental changes giving insights into possible adaptation and survival strategies under climate change.