First record of Undaria pinnatifida (Harvey) Suringar (Laminariales, Phaeophyta) on the Pacific coast of Mexico

Undaria pinnatifida, a laminarian kelp (Phaeophyta) native to Japan, Korea and northern China, has been introduced recently to the coast of southern California (USA). We present the first record of this invasive species on the Mexican Pacific coast, and show the current southern limit along the Pacific coast of North America. U. pinnatifida was found on September 28th, 2003, growing attached to small rocks on a sandy bottom in the subtidal zone at 12-14 m depth at Todos Santos Islands, in Baja California, Mexico. This population consisted of 15 sporophytes, with an average length of 50 cm and with mature sporophylls. This new finding suggests that the colonization of the Pacific coast of North America by this invasive species is still occurring, and its distributional range is expanding.