In the years 1932-52, Yoshiro Otsuki, while living in China, investigated how to cultivate Saccharina japonica var. japonica (Makombu) and Undaria pinnatifida (Wakame) in the Yellow Sea area in China. In 1938 he was able to develop a seeding method that could release numerous numbers of zoospores from mature Makombu and Wakame within several hours by stimulating the seaweed through partial drying of their thalli also known as “dry stimulation method ”. Consequently, he was able to establish the complete cultivation of Wakame using the raft cultivation method near the sea surface. However, Makombu has to be submerged on the seabed during the summer season because of too high temperature. Otsuki solved this problem by cultivating the gametophyte stage in the oligotrophic seawater below the sea surface and by this treatment, the gametophyte stage developed some form of resistance against environmental change. He was able to establish the complete cultivation technique of Makombu in 1952. However, he was not able to apply the technique in commercial scale in China as he had to return to Japan in 1953, just after being released from detention by the Chinese government. In Japan, he started the cultivation of Wakame in Onagawa, Miyagi Prefecture as soon as he returned home. This time he succeeded in the commercial cultivation of Wakame. Some Chinese researchers have evaluated his contribution to the establishment of cultivated technology of Makombu in Yellow Sea, where it does not grow naturally. Unfortunately, Otsuki's achievements have been almost unknown to the Japanese-both to the general public and the fishermen.

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In Japan, deployment of substrata has been employed to expand macroalgal beds as the local fishing grounds in shallow waters. However, most of them were left without any management. In our study site, Uchiura Bay, central Pacific coast of Japan, unmanaged two cuboid concrete blocks (3.5 × 3.5 × 0.5 m) were left with dominance of diadematoid sea urchins and crustose coralline algae. To probe the possibility of restoration of macroalgal beds on such unmanaged blocks, we kept small number of sea urchins on one (treated) of the concrete blocks. Further, we monthly investigated dominant macroalgal species and number of sea urchin on the two blocks (treated and control) between June 2012 and December 2014. The annual kelp, Eckolonia radicosa, formed dense stands on the treated block throughout the study period, especially on the edge of the block. On the contrary, the dense stands hardly appeared on the control block because of the persistence of sea urchins with a large number (113.8 ± 5.9 inds. in average). The present study showed that restoration of macroalgal beds is possible even on the long-left concrete blocks, but continuous monitoring and management (control of density of herbivores) are needed.

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