Introduction of exotic species may cause serious consequences for marine ecosystems. On the shores of the Cantabrian Sea (North of Spain) there is no routine examinations of seaweeds combining molecular and morphological methods for early detection of exotic species and thereby to assess in early stages their establishment and expansion processes as a result of anthropogenic activities (e.g.: shipping, aquaculture, etc). In this work we conducted molecular barcoding (COI and RbcL genes) of red

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... lgae collected in Asturias, Bay of Biscay (Gijón and Candás harbours). The results reveal the presence of the exotic Asian seaweeds (Pachymeniopsis gargiuli, Grateloupia imbricata Holmes and Grateloupia turuturu Yamada). This study constitutes the first report where the presence of these asian algae in this area of the Bay of Biscay is confirmed. The work demonstrates the success in combining morphological and genetic methods in the early detection of exotic algae and proposes that the "molecular barcoding" must be made primarily using the Rbcl gene. The COI Databases are still incomplete and imprecise to obtain successful results in red algae species-level identifications.