We investigated the invasion history and geographic distribution of marine nonnative species anthropogenically introduced to or within Japan using a questionnaire survey that was distributed to experts in such academic fields in 2022–2023. A total of 7,458 records on their occurrence in the field or at aquaculture facilities, including published and unpublished records, were reported by 36 respondents. According to the criteria for determining nonnative species by Iwasaki (2004a), we found 112 nonnative species that were introduced from abroad to Japanese waters (nonnative species with foreign origin), 63 native species introduced from abroad (nonnative populations with foreign origin), 46 native species introduced within Japan (nonnative species with domestic origin), and 60 cryptogenic species whose native areas have been unclear. Of the 112 nonnative species with foreign origin, 77 were unintentionally introduced with ballast water, ship fouling, or imported live fish and shellfish for aquaculture, and remaining 35 were introduced intentionally for aquaculture, fish baits, or as ornamental aquatic plants. For the taxonomic groups of the nonnative species, 16 species were pathogens (four viruses, six bacteria, three platyhelminths, etc.), and 95 others were non-pathogens (five cnidarians, 25 mollusks, 10 annelids, 33 arthropods, eight ascidians, 10 fishes, etc.). The rate of introduction per decade, as revealed by the first year of relevant data collection in Japan, increased after the 1950s to 1990s with a maximum of 26 species per decade and thereafter decreased. Understanding the import and domestic transport of live fish and shellfish needs more effort, and reinforcing legislative management is essential for controlling marine nonnative organisms.
Iwasaki et al. (Thu,) studied this question.