Growth rate variability of Pacific saury, Cololabis saira, larvae in the Kuroshio waters

Abstract

AbstractGrowth rate time series of Pacific saury, Cololabis saira, larvae in the Kuroshio waters were constructed using a previously reported relationship between early life stage growth rates and environmental factors in winter (January to March) 1971–2000, including sea surface temperature, chlorophyll a concentration and copepod density. Pacific saury has been commercially exploited and its stock size shows large fluctuations. It spawns from autumn to spring. Growth and survival in the early life stage have been considered the major factors controlling recruitment fluctuations. The winter spawning cohort showed a fast and stable growth rate during their early stage. Ages of 40 mm juveniles (t40) calculated from growth rate estimations were stable during the 30‐yr period and showed a significant positive correlation to the Pacific Decadal Oscillation index in winter. A negative correlation between the t40 and the catch record of medium size saury (24.0–28.9 cm) was detected but was not significant. Recruitment of the winter spawning cohort is thought to be regulated not only by the duration of the vulnerable larval period but also by other biological factors, i.e. mortality after the larval stage and the abundance of predators.