Occurrence and diversity of barnacles on international ships visiting Osaka Bay, Japan, and the risk of their introduction.

The occurrence and diversity of barnacles attached to the hulls of two intercontinental bulk carriers were studied at the port in Osaka Bay, Japan, to assess the potential risk of introduction of exotic species to the inner part of the bay. Barnacles were sampled from the bulbous bows, near the midship draft marks, and around the propeller posts and rudders. Twenty-two species were found, with 14 of these not previously recorded in Osaka Bay, including four species not previously recorded elsewhere in Japan. From an assessment of environmental similarity between Osaka Bay and native ranges, of the 14 species, Elminius modestus and Amphibalanus variegatus were considered to have the highest risk of introduction to the inner part of the bay.