Variations in female swordtip squidUroteuthis edulislife history traits between southern Japan and northern Taiwan (Northwestern Pacific)

Abstract

Swordtip squidUroteuthis edulisis a commercially important species in coastal waters throughout the Northwestern Pacific, including those of Japan and Taiwan. Despite the importance ofU. edulisto fisheries, previous studies on the life history traits (growth rate, size at maturity, and fecundity) of its populations in the Northwestern Pacific have been localized and region specific. Thus, we report life history traits of female swordtip squid from the waters off southern Japan and northern Taiwan, to identify seasonal variations within each population, as well as geographical variations between them. Variations in life history traits, including growth rate, mantle length (ML) at maturity, and female reproductive traits (gonadosomatic index, fecundity and egg size), are described and recognized to vary seasonally in both populations. Winter spawners in Japan have the highest growth rate, followed by spring spawners and summer spawners. Spring spawners in Taiwan mature at a younger age than autumn spawners. Geographical variations between populations are reported: fecundity level and egg size of spring spawners in Japan differ from those of spring and autumn spawners in Taiwan, but those of summer spawners in Japan are similar to those of spring and autumn spawners in Taiwan. Data on seasonal and geographical variations in life history traits ofU. edulisare useful for effective squid fisheries management.