Comparison of growth histories of immature Japanese common squid Todarodes pacificus between the autumn and winter spawning cohorts based on statolith and gladius analyses

Abstract

Growth of the autumn and winter spawning cohorts of the Japanese common squid Todarodes pacificus was examined based on daily growth increments in the statolith and gladius. The samples were taken from three groups of young (≤180 days old) squid: the autumn cohort collected in the Tsushima Current and the winter cohort collected in the Pacific near the coast and 1100 km offshore. The growth rate based on statolith analysis was highest in the winter cohort near the coast and similar in the two other groups. The daily growth based on gladius analysis during the month before capture was also highest in the winter cohort near the coast, and fluctuated more in the autumn cohort than in the winter cohort. The results suggest that gladius growth increments will be an important tool in future studies of growth in T. pacificus.