Fecundity of snow crab Chionoecetes opilio off Wakasa Bay in the Sea of Japan

Abstract

To determine fecundity, female snow crabs Chionoecetes opilio were caught off Wakasa Bay. The number of oocytes for pubescent females (prior to the terminal molt; mean carapace width 66.2 mm previously reported off Wakasa Bay) and for young adults (spawners less than 4 years after the terminal molt; 77.4 mm) correlated with the carapace width. However, the number of oocytes for pubescent females was 62.8% that of young adults. The difference in the number of oocytes might be caused by the body size when they developed their ovaries. Because the number of eggs attached to pleopods for primiparae (primary spawners) and young multiparae (repeat spawners within 1.5 to < 4 years after the terminal molt) originated during the ovarian development of pubescent females and young adults, respectively, the number of eggs for primiparae was 66.3% that of young multiparae. The number of oocytes and eggs for aged multiparae (more than 4 years after the terminal molt) was less than those for young multiparae and there was no correlation with their carapace width, probably because of the decline of ovarian activity in addition to insufficient number of sperm to accomplish full fertilization.