Bull. Jpn. Soc. Fish. Oceanogr. 69(2), Page 91-98, 2005   Characteristics of a Red Tide due to the Harmful Dinoflagellate Karenia mikimotoi Occurred in Usuki Bay, Oita Prefecture, in 2003 Kazuyoshi Miyamura†, Takafumi Mikajiri and Ken Kanazawa †e-mail: