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[Some examples of introductions and transfers of mollusks].

Human beings have always introduced non-indigenous species into new environments. Such is the case with shellfish, which the Romans, fine connoisseurs, transferred from France to Italy to mature. The Pacific oyster (Crassostrea gigas) and the Manila clam (Ruditapes philippinarum) are among the most significant examples of these introductions. The author examines the causes, conditions, results, and economic and biological repercussions of these examples. The well known cases of the introduction and implantation of new populations of molluscs are relatively recent, dating back to the beginning of this century. These movements result from an intensification of fishing activities, and the development of the mollusc industry and of transportation. The introduction of fish has been attempted for hundreds of species, whereas the introduction of molluscs has involved no more than a few dozen recorded species. Finally, with regard to the deliberate introduction of molluscs, none has led to significant ecological disruption, but on the contrary, has led to the establishment of permanent coastal activities which do not greatly disturb the natural biotopes.