Fisheries Research Institute, Toyama Prefectural Agricultural Forestry and Fisheries Research Center, Namerikawa, Toyama 936-8536, Japan
To clarify the growth of female beni-zuwai crab Chionoecetes japonicus, they were collected from the central part of Toyama Bay at the depth of 1060-1270 m by beam trawls from 2006 to 2011. Carapace width (CW) measurements revealed 9 and 2 modes in the size frequency distribution in juvenile and immature, and adult female, crabs respectively. Dividing into each normal distribution by the Hasselblad method, the mean size in CW was estimated to be 6.3, 9.0, 12.8, 18.0, 24.4, 33.2, 43.2, 56.1 and 66.1 mm in juvenile and immature crabs, and 68.5 and 81.5 mm in adult crabs, which were thought to mean CW at the 3rd to 11th instars and 11th to 12th instars, respectively. The size frequency distribution showed that most females would experience terminal molt at the 10th instar and grow into adult females at the 11th instar.