Nemopilema nomurai

Nemopilema nomurai is a large rhizostome jellyfish that grows to approximately 200 cm bell diameter and 200 kg wet weight. It is probably distributed predominantly in the northern East China Sea, Yellow Sea, and Bohai Sea, but may also be advected northward by the Tsushima Current into the Sea of Japan. For most of the last century, it was not abundant in the coastal waters of Japan; during such 'normal' years (e.g. 2001) only one or two medusae per week were caught in any particular set-net. In contrast, N. nomurai occurred at exceptional abundances around Japan during 1920, 1958, 1995, 2002, 2003, 2005, and 2006; during such 'bloom' years up to 1500 medusae have been caught in a set-net in a single day. Preliminary observations in the Tsushima Current during May-June 2007 indicate the largest bloom since 2002 is currently on its way toward Japan.