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Chub mackerel, Scomber japonicus, is a species of major importance to fisheries, particularly in eastern Asia. To aid in the sustainable management of this fisheries resource, we isolated eight novel microsatellite loci from the fish and examined their polymorphisms to estimate genetic variability. Genetic variability differed at each locus. The number of alleles ranged from 5 to 14, and observed and expected heterozygosity ranged from 0.43 to 1.00 and 0.50 to 0.86, respectively. One locus showed significant Hardy-Weinberg disequilibrium. No linkage disequilibrium was found. The high variability revealed in this study suggests that these microsatellite markers could prove to be a useful tool for further conservation genetics studies.

First annulus formation and age determination of otoliths were examined for chub mackerel Scomber japonicus collected in Korean waters over the one year from January to December in 2009. Translucent zone was regarded as an annual mark. Age interpretation criteria was based on the data of the number of translucent zone, capture date, and edge type of the otolith, assuming the nominal birthday to be 1 January. Monthly changes in mean marginal index indicated that translucent zone was formed once a year, mainly in June. The otolith of 0-ring group was detected comparing the progression by month of the smaller fish length, appearing to be a single first opaque zone. The average distance from the core to the first translucent zone was ~1.77 mm, provided as supplementary information to increase ageing accuracy. The ageing criteria for chub mackerel was made to determine correct year-class with the purpose of effective stock assessment. This method using nominal birthdate and edge type analysis could estimate age of fish closer to the true age than purely counting the number of translucent zone on a whole otolith.