The clam-eating alien snail Euspira fortunei and its impact for clam culture in Japan

菲律宾蛤仔（Ruditapes philippinarum）是日本重要的渔业资源。由于日本的产量逐渐减少，近年来从中国和韩国进口了蛤蜊，为水产养殖提供种子，也为休闲贝类采集提供种子。本研究的目的是确认外来物种是否与蛤蜊一起被引入，并获得有关它们在日本沃茨分布的信息。从装有R. fortunei、Glossaulax didyma和Glossaulax reiniana的麻袋中采集到3种食软体动物的月螺。从中国和朝鲜进口。其他七种腹足类，九种双壳类，包括文蛤，钱包蟹Philyra豌豆，和腕足类，Lingula爪，也收集了从麻袋。几乎所有无意引入的动物都是活的，并直接与商业引入的蛤蜊一起被渔民合作社释放到宫城县的Mangoku-ura Inlet。虽然蜗牛E.在日本东部和北方海岸，并不是本地产的，但在滨名湖（静冈）、Obitsu河河口（千叶）、松川浦湾（福岛）、松岛湾（宫城）和Mangoku-ura湾的蛤生产区，数量相对较多。我相信这种入侵蜗牛的种群已经在日本水域中建立，并正在成为蛤蜊种群的新的、强大的捕食者。防止进一步扩散和估计捕食率对文蛤养殖具有重要意义。在本次调查记录的22种外来物种中，有7种也在本地社区中发现。外来人口对原有人口的影响也是需要解决的重要问题。

The Asari clam Ruditapes philippinarum is a commercially important fishery resource in Japan. Because the amount of production has been decreasing gradually in Japan, the clam has been imported from China and Korea in recent years to provide seed for aquaculture and also for recreational shellfish gathering. The object of this study is to confirm whether alien species are being introduced together with the clam and to obtain information on their distribution in Japanese waters. Three species of mollusk-eating moon snail, Euspira fortunei, Glossaulax didyma, and Glossaulax reiniana, were collected from sacks filled with R. philippinarum imported from China and North Korea. Seven other gastropod species, nine species of bivalves including Meretrix pethechialis, the purse crab Philyra pisum, and a brachiopod, Lingula unguis, were also collected from the sacks. Almost all the unintentionally introduced animals were living and were directly released with commercially introduced clams to Mangoku-ura Inlet, Miyagi Prefecture, by a fishermen's cooperative. Although the snail E. fortunei is not indigenous to the eastern and northern coasts of Japan, relatively large populations of it occur in the clam production areas of Lake Hamana (Shizuoka), the estuary of the Obitsu River (Chiba), Matsukawa-ura Inlet (Fukushima), Matsuishima Bay (Miyagi) and Mangoku-ura Inlet. I believe that a population of this invasive snail has already been established in Japanese water and is becoming a new, strong predator of the clam stocks. Prevention of further spread and estimation of the rate of predation are important to the clam culture. Among the 22 alien species recorded in this survey, seven were also found in the native communities. The effect of the alien population on the preexisting population is also important problem to be solved.