Variations in female swordtip squid Uroteuthis edulis life history traits between southern Japan and northern Taiwan (No
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ORIGINAL ARTICLE Biology
Variations in female swordtip squid Uroteuthis edulis life history traits between southern Japan and northern Taiwan (Northwestern Pacific) Yumeng Pang1 · Chih‑Shin Chen2,3 · Yoko Iwata1 Received: 30 March 2020 / Accepted: 24 August 2020 © Japanese Society of Fisheries Science 2020
Abstract Swordtip squid Uroteuthis edulis is a commercially important species in coastal waters throughout the Northwestern Pacific, including those of Japan and Taiwan. Despite the importance of U. edulis to 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 of U. edulis are useful for effective squid fisheries management. Keywords Swordtip squid · Uroteuthis edulis · Life history traits · Northwestern Pacific
Introduction Squid typically grow fast and have short life spans and flexible life history traits, which enable them to respond rapidly to changing environmental conditions (O’Dor and Webber 1986; Rodhouse 2001; Pecl and Jackson 2008; Xavier et al. * Yumeng Pang [email protected]‑tokyo.ac.jp Chih‑Shin Chen [email protected] Yoko Iwata [email protected]‑tokyo.ac.jp 1
Atmosphere and Ocean Research Institute, University of Tokyo, 5‑1‑5 Kashiwanoha, Kashiwa, Chiba 277‑8564, Japan
2
Institute of Marine Affairs and Resource Management, National Taiwan Ocean University, Keelung 20224, Taiwan, ROC
3
Center of Excellence for the Oceans, National Taiwan Ocean University, Keelung 20224, Taiwan, ROC
2015). The ambient environment of a squid varies seasonally and geographically, which can greatly affect its life history traits, particularly its growth, maturity, reproduction and migration (Chen and Chiu 2003; Moreno et al. 2005; Pecl et al. 2004a; Pierce et al. 2008; Rodhouse et al. 2014), and lead to great variability in its annual abundance and distribution patterns (Dawe et al. 2000; Rodhouse 2001). For example, trends in abundance of Loligo bleekeri were largely driven by latitudinal differences in envi
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