Reproductive biology of Pasiphaea japonica females in Toyama Bay, central Japan

Abstract

The reproductive biology of female Pasiphaea japonica, including the minimum size of females carrying embryos, spawning and hatching seasons, and brood size, was examined in Toyama Bay, central Japan, during 2004 through 2007. Sampling was conducted onboard a commercial seiner and a fisheries research vessel. The minimum size of ovigerous females was 47.7 mm body length. The percent occurrence of ovigerous females increased with body size, reaching 50% at 57.9 mm body length. Ovigerous females occurred all year round with a seasonal change in percent occurrence, ranging between 41.5 and 94.3% of the total observed females. Consequently, reproduction in females seems to occur throughout the year in Toyama Bay, with seasonal differences in reproductive intensity. Spawning intensity was high during April–July and October–January based on the occurrence of the early developmental stage of embryos, while hatching intensity was high in October–May based on the occurrence of embryos just before hatching. Brood sizes were similar at the same size of body length regardless of embryo stage, except just after spawning.