Abstract
In total, 57 giant squid, Architeuthis dux, were found between January 2014 and March 2015 in Japanese coastal waters in the Sea of Japan. Occurrences were especially high around Sado Island and in Toyama Bay. All of the squid occurred individually, and 28 were found alive. The occurrences were categorized into three groups based on distance from the shore and the depth at which they were found: (1) washed ashore on a beach or found floating at the surface close to a beach (19 individuals); (2) caught in a fixed net set in coastal waters between 50 and 150 m depths (28 individuals); and (3) caught by bottom trawl or bottom gillnet fisheries several kilometers offshore between 200 and 300 m depths (ten individuals). Two size groups were recognized, one ranging between 80 and 160 cm dorsal mantle length (DML) with a mode at 110 cm and another larger than 160 cm DML. The sex ratio in the smaller group was nearly equal and the larger group was comprised of all females. The Sea of Japan was considered to be a large natural trap for giant squid migrating through southwestern Tsushima Strait.