The urchin barren has increased and maintained along the coasts of Kochi Prefecture, Japan. In these urchin barrens, Anthocidaris crassispina and Echinometra spp. dominate on bedrock and boulders. Algal succession and density of invading sea urchins were studied after removing sea urchins at five stations (Kamikawaguchi, Ikenoura, Kutuu, Tei and Sakamoto). In 2009, fishermen, students and volunteers removed sea urchins by skin and scuba diving at Kutuu. Sargassum duplication, S. assimile and S. tenuifolium growing in adjacent areas colonized coralline covered bottoms within a year. Removal of sea urchin was the most effective method to regenerate seaweed bed at Kamikawaguchi, Kutsuu and Ikenoura. In contrast, at Tei and Sakamoto, we also have to reduce the browsing activity of herbivorous fishes. Sustainable cooperative activities are needed among fishermen, students and volunteers.
