Larval and juvenile growth of chub mackerel Scomber japonicus in relation to recruitment in the western North Pacific

Abstract

To detect indices of recruitment intensity of the Pacific stock of chub mackerel Scomber japonicus, the relationship between the growth rate during early life and recruitment variability and the effects of temperature on annual change of the growth rate were examined. Growth-trajectories in larval and juvenile stages were back-calculated by otolith microstructure analysis using juveniles collected in the Kuroshio–Oyashio transition region of the western North Pacific in May and June from 2002 to 2011. A total of 532 otoliths were analysed. Hatch dates were distributed from mid-March to mid-May and most chub mackerel hatched in April. Mean daily growth rates ± standard deviation (SD) of the April cohort in larval and juvenile stages ranged between 1.03 ±0.10 (2006) and 1.52 ±0.23 mm day−1 (2009). The mean daily growth rate and larval stage duration were significantly related to recruitment which had been estimated by virtual population analysis. The results indicated the growth rate of the April cohort was an important index of year-class strength. There was a significant correlation between sea surface temperature experienced by each fish and the mean daily growth rate during the larval period. Higher water temperature led to faster growth and shorter larval stage duration of the April cohort of the Pacific stock of chub mackerel.