seaweed

" Between 1981 and 1994 world production of seaweed increased from 3.2 million tonnes (fresh weight) to nearly 7 million t. The seaweeds that are most exploited are the brown algae with about 5.2 million t (75％) followed by the red algae (1.73 million t; 25％) and a small amount of green algae (about 0.5％). The seaweed that is most cultivated in the kelp Laminaria japonica, which accounts for most of Chinese production (about 3.8 million t). Laminaria japonica is the most important economic seaweed in China. Mariculture on artificial floating rafts started in 1952 and production increased steadily until 1980 when the highest production of 252,907 dry tons (about 1,500,000 wet tons) was achieved. In the late 1980s, the cultivation area and total yield declined due to the development of shellfishculture as farmers preferred cultivating shellfish to kelp. Currently, the yield of kelp seems to be about 700,000 dry tons, amounting to some 3,500,000 wet tons, but precise figures are difficult to get."