Estimation of age, growth and maturation of purpleback flying squid, Sthenoteuthis oualaniensis, in Bashi Channel, central Pacific Ocean

Beak Microstructure Estimates of the Age, Growth, and Population Structure of Purpleback Flying Squid (Sthenoteuthis oualaniensis) in the Xisha Islands Waters of the South China Sea

“…The age structure in our results was approximately half a year, belonging to the dwarf form. This result is also similar to the age structures of forms caught in the Bashi Channel, eastern tropical Pacific Ocean, and western waters of the Philippines [22,23,62,63].…”

“…If more mature females are sampled in a given area, this could indicate that the area serves as a spawning ground [71]. According to our results, we suggest that the waters around the Xisha Islands are not the spawning grounds of the autumn-winter hatching group, because mature squid accounted for less than 50% of the total samples [63,71]. We found a significant sex difference in the relationship between mantle length (ML) and age.…”

“…Previous studies have estimated the life span of S. oualaniensis in other areas of the South China Sea with statolith increments; these life spans have mostly been 1-4 months, except for squid collected in the western waters of the Philippines (life span: 95-275 days, 3-9 months) [23,24,26,27,61]. For example, the life span of squid in the Bashi Channel, the eastern tropical Pacific Ocean, the northern Pacific Ocean, and the Bay of Bengal is approximately 2-6 months (53-155 days, 84-168 days, 52-186 days, and 40-120 days, respectively) [22,25,62,63] (Table 2). In addition, squid in the western waters of the Philippines have an estimated life span of 3-9 months (95-275 days) [23].…”

“…Spring and summer hatching groups of S. oualaniensis in the northwestern Indian Ocean and Arabian Sea have been recorded, but mixed groups (consisting of four seasons) were also observed along the southwestern coast of India and in Taiwanese waters [4,5,58]. However, the peak hatching periods in the South China Sea, Bashi Channel, eastern tropical Pacific Ocean, and southeastern Arabian Sea were distributed in January, February, and December, representing the winter hatching groups [62,63,65,66] (Table 2).…”

Age and growth of the little Indian squid, Loliolus hardwickei (Gray, 1849) in the Arabian Sea

“…Sexual dimorphism, where females are larger than males, is common among the genus Loliolus (Lu et al ., 1985). Advancing maturation of males is thought to be a characteristic for all cephalopods (Gonzalez et al ., 1994) and was also observed in other loliginid species (Arkhipkin, 1995; Jackson et al ., 1997) and ommastrephids (Arkhipkin & Silvanovich, 1997; Markaida et al ., 2004; Liu et al ., 2017). Male maturation is not as energy-demanding as female maturation, and this could be a reason for the difference in age-at-maturity between males (52 days) and females (62 days).…”