Age, growth, and population structure of the red flying squid (Ommastrephes bartramii) in the North Pacific Ocean, determined from beak microstructure

To explore the feasibility of using beak microstructure to estimate the age of oceanic squid, sagittal sections in the upper beak were used to validate the age of the red flying squid (Ommastrephes bartramii) in the North Pacific Ocean. The growth rates of mantle length (ML) and body weight (BW) were estimated on the basis of beak increments. We compared growth curves derived from previous statolith-based studies and those from this study. Results indicate that the mean age of females and males was 203 d (standard deviation [SD] 55) and 180 d (SD 45). The hatching period occurred during October–June of the following year, and hatching peaked during January–April on the basis of back-calculation. All sampled squid belonged to the winter–spring cohort. Females and males had a similar growth pattern in ML and BW with increased ages, except for male ML after age 301–350 d. An exponential model best described the relationships between age and ML as well as BW for both sexes. The difference in growth curves and lower growth rates reported here, compared with those of previous studies, may result from different stock structures and extreme weather. This study confirmed that beak length works well for estimating the age of oceanic squid.