First record of the calanoid copepod Acartia omorii (Copepoda: Calanoida: Acartiidae) in the southern bight of the North Sea

The occurrence of the calanoid copepod, Acartia omorii, is reportedfor the first time in the coastal waters of the Southern bightof the North Sea, off Calais harbour. Acartia omorii males andfemales were consistently found in four plankton samples. Thecollected specimens were compared with A. omorii individualscollected from the type locality (Tokyo Bay, Japan). The captureof A. omorii, a species native to Japanese coastal waters, isin agreement with the recent observation of the Japanese macroalgaeUndaria pinnatifida within Calais harbor and the hypothesisof passive transport in ship’s ballast water.