In December 1992, some sporophytes of the Asian kelp Undaria pinnatifida were found growing subtidally at 6 m depth below `A . Storni' Port, Puerto Madryn, Argentina . During the winter of 1994, the species expanded significantly from its original location . Sporelings appear in early autumn and attain their maximum size (1 .65 ± 0 .10 m) during winter and early spring, when most of them become fertile . The fronds are lost in summer, with only some holdfasts and sporophylls surviving, and these disappear by the end of summer . The occurrence of U. pinnatifida in Golfo Nuevo is reportedly due to an accidental introduction by cargo ships or fishing vessels arriving from Asian ports .