2004 年 59 巻 p. 22-44
To investigate the invasion history and recent geographic distribution of marine organisms introduced to Japan or transferred domestically to non-native regions, a questionnaire survey on their occurrence in the field, including both published and unpublished records, was conducted in 2002-2003. A total of 105 taxa was reported by 94 respondents. According to three criteria, viz. known or unknown geographic origin, established invasion history, and presumed dispersal mechanisms associated with human activities, 42 taxa were designated as non-indigenous species introduced to Japan through human activities, 26 taxa as indigenous species that are distributed both in Japan and other countries but are introduced from abroad to Japan for fisheries or as fish bait, 20 taxa as cryptogenic species which are not demonstrably native or introduced, two taxa as non-indigenous species that have extended their range to Japan through natural dispersion, and one taxon as an indigenous species. The remaining 14 taxa were considered to have been transferred domestically to new areas. Analysis of the years of first record of 42 non-indigenous species suggests that the rate of invasion has increased over the past century, with seven or eight species being introduced per decade after 1960. Data on temporal change in geographic distribution revealed that many non-indigenous species have become widespread recently, from the Pacific coasts of central Japan to the coasts of the Sea of Japan or northward. However, the species listed in the present study are not exhaustive, and more extensive investigations covering all taxa and all presumed dispersal mechanisms are urgently needed before consideration of legislative management of introduced marine organisms.