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A baseline study of the occurrence of non-indigenous species in Danish harbours

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Jesper Harbo Andersen, Emilie Kallenbach, Mathias Brink Kjeldgaard, Steen Wilhelm Knudsen, Wenche Eikrem, Camilla With Fagerli, Eivind Oug, Trine Dale, Jens Thaulow, Janne Kim Gitmark, Anders Hobæk, Norman Whitaker Green, Martin Hesselsøe, Josianne Støttrup, Jesper Kuhn, Dorte Bekkevold, Lars Magnus Wulf Jacobsen, Peter Rask Møller, Christian Aakjær Olesen, Henrik Carl, Frank Stuer-Lauridsen


We report the first ever nation-wide study of the occurrence of non-indigenous species in Danish harbours. The sampling was car-ried out using both conventional and biomolecular methods (eDNA). In total, 16 harbours were covered – Esbjerg and Aarhus, the two largest harbours in Denmark, with intensive sampling and 14 harbours with a reduced programme. 26 non-indigenous species were recorded using conventional sampling and 13 species were recorded using eDNA-based methods. Excluding overlapping rec-ords, we have recorded a total of 34 non-indigenous species in the 16 harbours studied. Based on the results, we conclude the following: 1) more non-indigenous species are found in the western parts of Denmark (North Sea region) then in the eastern parts (Baltic Sea), and 2) a few species previously unseen in Danish marine waters were recorded, i.e. the two bristle worms Eteone het-eropoda (fam. Phyllodocidae) and Streblospio benedicti (fam. Spionidae). Further, we provide a proof-of-concept regarding the overarching objectives of the MONIS 1-3 projects and the eDNA-based test systems developed. The results constitute a baseline for future studies in Danish ports and other hotspot areas.