Abstract: To understand the age and growth of neon flying squid (Ommastrephes bartramii) in the eastern and western cohorts, we analyzed their age and growth characteristics based on the samples collected in North PacificOcean in 2010, 2012, 2015 and 2016. The results showed that the life cycle of O. bartramii was approximately one year. The age of the eastern cohort ranged from 133 to 345 d, while the age of female and male in the western cohort ranged from 105-271 d and 95-264 d, respectively. The peak hatching date of the eastern cohort was distributed in August to October. In terms of western cohort, the peak hatching date of the female was distributed in January to April, and that of the male was distributed in February to April. The relationship between mantle length and body mass showed that the growth parameter b value (2.98) was closer to 3 for eastern cohort, indicating a constant growth rate of O. bartramii. The growth parameter b value (3.17 for female and 3.14 for male) were greater than 3 for western cohort, indicating a positive allometry. The relationship between mantle length and age of eastern cohort was in accordance with Logistic function, in which the inflection point of the age was 177 d and the inflection point of mantle length was 261.90 mm. The relationship between mantle length and age of western cohort was in accordance with Gompertz function, in which the inflection points of the age were 76 d for female and 74 d for male, and the inflection points of mantle length were 142.49 mm for female and 137.48 mm for male, respectively. With the increases of age, the growth rate of eastern and western cohorts showed a downward trend. The growth rate of eastern cohort was higher than that of the western cohort, while the growth rate of females in the western cohort was slightly higher than that of males.

Key words: Ommastrephes bartramii, growth inflection point, North Pacific Ocean, statolith.