The productivity of Cladosiphon okamuranus culture was examined in the field. For the purpose of performing this study a culture-net on which the zoospores naturally attached themselves in the field was used and the net was set in the open sea.
1) Concerning the suitable depth at which this plant grew, the most suitable depth was ascertained to be at 2 meters below the low-tide level, and the second was at 1 meter, the third, at 3 meters and the fourth, at 4 meters, respectively.
2) After setting of the culture-net, the plant on the net showed gradually accelerated growth until it reached maximum flourishing between the 80th and 90th day. Since no further flourishing thereafter was observed at 2 meters in depth, it seemed safe to say that the best harvest time fell during a 10-day-period between the 80th and 90th day after net-setting.
3) The harvest from one sheet of culture-net (1.5×18.2 m) of the plant was 65 ?? 100kg in wet weight. Based on the above-mentioned findings, it seemes feasible to commercialize the artificial cultivation of this plant.