Variations of life history parameters in two geographical groups of the neon flying squid, Ommastrephes bartramii, from the North Pacific

The neon flying squid, Ommastrephes bartramii (Lesueur), is a widespread subtropical to temperate species, and is composed of several tempo-spatial groups in the North Pacific. We analyze the growth parameters of two allopatric stocks with two seasonal cohorts using statolith microstructure, and propose a tempo-spatial migration model. We used 571 statoliths, obtained from juvenile/adult squids (175–527 mm mantle length, ML). Based on precise digitized statolith growth marks, various early life demographic traits were estimated by the back-calculation method. Two cohorts of autumn and winter were identified in the northeastern (NE) North Pacific, while only a comparable winter cohort was found in the northwestern (NW). There was a significant difference in the relationships of statolith radius (Ra) to increment numbers (In) between NE and NW stocks. However, linear ML to Ra relationship exhibited no geographic difference in large females (>350 mm ML), but significant difference between NE and NW in both small females (