Age and growth of the neon flying squid, Ommastrephes bartrami, in the North Pacific ocean

Abstract

Longitudinal sections of statoliths were observed by light microscopy on 237 individuals (158–510 mm mantle length, ML) of Ommastrephes bartrami, obtained from the North Pacific (26 °–46 °N, 143 °E–149 °W) during 1991–1994. The width of each increment sharply decreased from 5–7 μm to about 1–2 μm between the 80th and 100th increment, with a transition zone where increments were inconspicuous. ML-age relationships were linear, and slope and intercept values differed by geographic area, hatch season and sex. Overall growth rates (mm day −1) were generally higher in females (1.1–2.5) than in males (1.1–2.1). Since these values were similar to the growth rates of four individuals which were tagged and recaptured (0.8–2.4), the increments were assumed to be formed daily. The growth rate was highest for individuals hatched in summer, followed by those hatched in spring. Growth rate obtained by length-based methods may be underestimated. The hatch dates of neon flying squid are almost year-round, and the life span is likely 1 year since mature individuals were 7–10 months old.