Eight experimental fishings with crab traps were made to study the spatial distribution pattern of snow crab Chionoecetes opilio on the bottom of a bank known as the Yamato-tai located in the center of the Japan Sea. The size of the terminal molt crab was comparatively examined for three regions, i. e. Yamato-tai in the Japan Sea, coastal waters of the Japan Sea off Kyoto Prefecture, and coastal waters of the Pacific Ocean off Fukushima Prefecture.
Adult females were mainly distributed in an area shallower than around 320m in depth in conditions of a gradual down ward slope with a muddy bottom. On the other hand, males were distributed in all survey areas from 290m to 349m in depth.
Terminal molt males were divided into five groups with average carapace sizes of 64.9mm, 80.5mm, 96.4mm, 110.5mm, and 125.0mm. Adult female sizes of terminal molt females was 69.8mm. These sizes were 10-20mm smaller than the terminal molt size of crabs obtained from the coastal areas off Kyoto and Fukushima Prefectures.