SEAWEED CULTURE IN JAPAN 



ROBERT WILDMAN' 



The culture of marine algae, primaril\ for human 

 consumption, is a large and expanding industry in 

 Japan. At the present time, the growing and har- 

 vesting of Porphyra, "nori,"" is considered to be 

 one of the most profitable fisheries in Japan. In con- 

 trast, seaweed culture is still in a research phase in 

 the United States. Our demand for marine algae is 

 much more limited in terms of both total volume 

 and number of species. This is mainly due to the 

 fact that few Americans eat the plants as such. Our 

 use of seaweed is almost entirely in the form of 

 phycolloids extracted from the plants, and to a very 

 limited degree, as fertilizers and food. These uses of 

 several species of marine algae and the recognition 

 that the U.S. possesses a limited supply of the three 

 or four most used species has led to seaweed cul- 

 ture on an experimental basis in this country. How- 

 ever, we have not and, in the foreseeable future, 

 will not place the amount of our coastal waters 

 under '"cultivation" as has Japan. Another impor- 

 tant difference between the United States and 

 Japan is that the seaweed beds can be harvested 

 only by fishermen's cooperative associations in 

 Japan whereas in this country the harvesting is done 

 by industrial firms either directly or through con- 

 tractors. The cooperatives are responsible for the 

 management and protection of these resources 

 while in the United States such efforts are rarely 

 required by the government but are usually volun- 

 tary. 



PORPHYRA (NORI) 

 Culture Techniques 



The most extensively cultivated seaweed in 

 Japan, nori. has been groun since about 1600 (Ta- 

 mura. 1966). The earl v culture techniques consisted of 

 setting bundles of twigs in estuaries on which the 



' Prognim Director. OtTice of Sea Grant. NOAA. Washing- 

 ton. D.C. 20:.\v 



spores settled and grew, and the mature plants were 

 harvested. The nori harvest grew gradually until the 

 end of World War 11 and is now six times that of the 

 prewar level. Much of this increase was made possi- 

 ble by dramatic improvements in culture techniques. 

 Two other factors were the establishment of 

 cooperative unions which increased the profit to the 

 grower and increasing coastal eutrophication which 

 resulted in more fertile waters in many new areas, 

 while the latter is the less important factor. 



At first bamboo twigs replaced the tree twigs, then 

 these were replaced in many areas by nets which 

 were still placed in the water to collect the spores. 

 This use of net collectors is thought to be responsible 

 for a doubling of production, but the discovery by K. 

 M. Drew of the Conchocelis stage in the life history 

 o{ Porphyra enabled the Japanese to make the in- 

 creases in production to the current level. The 

 fisherman or cooperatives are now able to artificially 

 "seed" their nets through the controlled culture of 

 the Conchocelis stage, which in turn releases the 

 spores to attach onto the nets in tanks or in the sea. 

 (See Suto's paper in this report for a complete de- 

 scription of this process.) When the nets are "in- 

 noculated" in tanks, the nets are rotated slowly in 

 the tanks containing the Conchocelis and then trans- 

 ported to the growing area where they are attached 

 to the bamboo poles. This procedure allowed the 

 nori grower to control the seeding of his collectors 

 and thus, be more confident of his crop in areas with 

 a good natural population. It also provided a means 

 of growing nori in regions which had experienced a 

 shortage in natural spores, especially in western 

 Japan. 



With the advent of the use of the Conchocelis 

 — spore culture technique, the predominant species 

 used changed from Porphyra lenera to P. yczoensis 

 which could withstand higher salinities. In many 

 areas P. tencra and P. yezoensis are grown in the 

 inner parts of bays and estuaries with P. 

 p.seiiilollneari.s being grown in the deeper waters. In 



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