 However, in the early 1970s, there were reports of a brown "Didemnum " ascidian on oyster beds in the region.Around the same time, oyster spat from Japan was introduced into the Pacific coastal regions of Canada and the USA and soon afterwards an ascidian was observed there, and later identified as "D. vexillum".By 2014, this tunicate was present in the eastern Atlantic, North Sea and Mediterranean Sea in the Netherlands, the United Kingdom, Ireland, France and Italy.