Clava multicornis (Forsskål, 1775): rediscovery of a North Atlantic hydroid (Cnidaria, Hydrozoa, Anthoathecata) on the Pacific coast of North America
The shallow-water hydroid Clava multicornis is reported from the west coast of North America for the first time in nearly six decades. A North Atlantic species often occurring on intertidal fucoid algae, it had been found elsewhere only in heavily-invaded San Francisco Bay, California, with records dating from the late 19 th to mid-20 th centuries. The species has not been reported from the Bay Area since 1954, in spite of intensive recent collecting, and it is presumed to no longer exist
... longer exist there. During the winter and summer of 2013, robust colonies (which were fertile in the winter) were discovered in fouling communities on floating docks further north in Coos Bay, Oregon. This estuary harbours a large number of introduced species from both the western Pacific and the North Atlantic. We suspect that C. multicornis was introduced to Coos Bay in one of two ways. One means of transport might have been in hull fouling on ships, either directly from the North Atlantic or possibly from another Pacific coast estuary where the species remains undetected. A second possibility is on fucoid algae used in the shipment of polychaete bait worms from the State of Maine, on the Atlantic coast of the United States.