Effects of hatch timing and sex on growth of the winter-spawning stock of Japanese common squid Todarodes pacificus migrating in the Pacific Ocean

Abstract

To identify factors aŠecting the somatic growth of the winter-spawning stock of Japanese common squid, the somatic growth of squid caught in the East China Sea, the Paciˆc Ocean and the Tsushima Strait from 2000 to 2011 was estimated using age determination from statolith microstructure analysis. The relationship between estimated age in days and dorsal mantle length wasˆtted using a Gompertz growth equation. The residuals of dorsal mantle length from the growth equation diŠered among year classes, hatch months, and sexes. Although no environmental factors correlated with the annual diŠerence in growth, increased sea water temperature in spring in the Kuroshio Oyashio transition region corresponded to increased growth with hatch month. Growth was smaller in males than in females during the southward migration, which suggested depressed growth in males due to earlier sexual maturation than in females.

Study on the Geographic Variation and Trophic Variation of Todarodes pacificus in Different Areas Based on Stable Isotope Information from the Gladius

“…T. pacificus plays an important role in the marine ecosystem [ 5 , 6 , 7 ]. To date, national and international scholars have studied the resource distribution [ 5 ], age [ 8 ], population structure [ 9 , 10 ], and reproduction of T. pacificus [ 11 , 12 ]. Studies have shown that T. pacificus in the Sea of Japan migrates northward for feeding and then migrates southward for spawning, and the trophic level of feeding increases during migration [ 3 , 13 ], but the feeding ecology and migration path of T. pacificus in the East China Sea are less known.…”