The long spawning season of the swordtip squid found in our study may be a strategy of this species to compensate variable environmental conditions that affect hatching (Melo and Sauer, 1999, Perez et al., 2002 and Boyle and Rodhouse, 2005). The relative high monthly GSI and percentage of mature individuals indicated that there were two major spawning seasons in the northeastern waters of Taiwan, autumn (with the peak in October) and spring (with the peak in April), and two spawning groups.