The culture of marine algae, primarily for human consumption is a large and expanding industry in Japan. At the present time, the growing and harvesting of Porphyra, "nori," is considered to be one of the most profitable fisheries in Japan. In contrast, 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 culture on an experimental basis in this country. However, we have not and, in the foreseeable future, will not place the amount of our coastal waters under "cultivation" as has Japan. Another important 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 contractors. 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 voluntary.


Culture Techniques

The most extensively cultivated seaweed in Japan, nori. has been grown since about 1600 (Tamura 1966). The early culture techniques consisted of setting bundles of twigs in estuaries on which the spores settled and grew, and the mature plants were harvested. The nori harvest grew gradually until the end of World War II and is now six times that of the prewar level. Much of this increase was made possible 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 of Porphyra enabled the Japanese to make the increases 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 description of this process.) When the nets are "innoculated" in tanks, the nets are rotated slowly in the tanks containing the Conchocelis and then transported 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 tenera to P. yezoensis which could withstand higher salinities. In many areas P. tenera and P. yezoensis are grown in the inner parts of bays and estuaries with P. pseadolinearis being grown in the deeper waters. In the former situation, the nets (18.2 m x 1.3 m) are stretched between bamboo poles stuck to the bottom, with the nets being tied at the mean water level. The nets with P. pseudolinearis growing on them float on the water surface, anchored to maintain their position, and kept on the surface by glass or plastic floats.

Recent work by Imada and co-workers has yielded results that could increase the production of nori. This research indicated that amino acids are effective growth promoting substances for Porphyra and that the exposure of the fronds to air by tidal fluctuations is a significant factor in disease control (Imada, Saito, and Teramoto, 1971). Crossing experiments by Suto between different species of cultivated Porphyra succeeded, the cross developing to the Conchocelis phase. Other attempts at crossing monoecious and dioecious species, and between species with different chromosome numbers were not as successful (Suto, 1971).

Production and Use

The demand for nori in Japan and the increasing production capability have resulted in a very significant industry. In 1970, about 60,000 hectares (150,000 acres) of coastal waters in Japan were being used for nori cultivation. This acreage produced nearly 6 billion sheets of the dried product worth 70-80 billion yen per year (approximately $230 million). Each paper-thin sheet is 20 cm (8 inches square and weighs about 3 g. In addition, 200 million sheets are imported from Korea, a number now limited by an import restriction and one which could be increased to 1 billion sheets in the future (see Suto).

Approximately 60,000 fishermen are now cultivating nori, setting about 10 million nets each year and realizing the 50% (Furukawa, 1971) to 70% (see Suto) net income for their efforts. This level of production is required to meet the needs of the average Japanese who consumes 50-60 sheets of nori per year. The price of nori, up to $15 per kilogram dry weight (nearly $7 per pound), is a major factor in making this the most profitable of all fisheries in Japan.

Problems and Needed Advances

In spite of the high level of productivity, the Japanese recognize the need to increase their pro-auction and improve the profit potential of this fishery. Briefly summarized, these problems and activities are as follows. (Again, see Suto's paper in this report for a more complete description of them.)

1. Development of new nori grounds or improvement of old ones, using the new net collector techniques, the floating net cultures and coastal engineering works (pilings to protect growing areas, deepening such areas to increase water exchange, etc.). This would bring new areas into production to replace old ones lost because of pollution and increase the productivity of existing areas.

2. Prevention of large-scale fluctuations (heavy losses) yearly production primarily through disease control. This is done partially now by preventing overcrowding of the nets in the growing areas and by refrigerating the "buds" (juvenile plants, 5-50 mm in length) at -20°C. This refrigerating procedure is applied to a large part of the newly hatched fronds essentially for the procurement of frond stocks. These stocks are used to replace poorer quality fronds in the growing areas. By refrigerating these buds, the "weeds" (such as Enteromorpha) and diatoms are killed, and the development of a parasitic fungus is prevented. By 1970, one-half of all culture nets used were refrigerated using this technique (Okazaki, 1971). Most of the diseases or diseaselike problems are not well understood, or, in many instances, not even identified. Frequently, the plants appear to be infected by a fungus, but this could be caused by environmental or physiological conditions (temperature, salinity, malnutrition, etc.). Most of these conditions are called various kinds and colors of "spot disease" or "rots," but the exact causitive agent is not identified.

Work reported recently by Ohio and his coworkers identified pollution from chemical plants as a cause of one type of algal disease. A "cancerous" disease observed in Porphyra in shallow coastal waters polluted by industrial wastes was shown to be related to contact between the fronds and the contaminated bottom mud. The mud was extracted and it was found that the carcinogenic fraction contained a mixture of organic compounds discharged by a dye factory which uses tar distillates as raw materials (Ishio, Yano, and Nakagawa, 1977).

3. Mechanization of nori cultivation and processing. With the current labor shortage in Japan and other industries drawing workers away from the fisheries, with the resultant rising labor costs, as much of the growing, harvesting, and processing of the nori must be mechanized as possible. Even so, the nori fishery is not suffering nearly as severe a problem as that facing the oyster fishery.

4. Eutrophication in the coastal areas around Japan. This, in fact, is going on, and it may provide nutrients to the nori cultivating areas to some extent, but most of the causative elements of coastal eutrophication such as industrial discharge, domestic sewage, and agricultural runoff contain undersirable constituents. Industrial pollution, particularly that which contains cadmium, mercury, and other highly toxic elements poses a much greater threat to nori cultivation. Pollution of all kinds is now a very serious problem for Japan, but their heavy dependence on seafood, much of which comes from their coastal waters, makes marine pollution a very real health and economic threat.

5. Potential for oversupply with its resultant economic effects. With the high prices, the growers are obviously attempting to increase their total production. The success of efforts to expand the nori growing areas, solve the disease problems, eliminate pollution problems, and mechanize the industry will all lead to increased production. Further, the growing tendency of separating the producers and processors into separate operations will cause the producers to grow more algae to maintain their income level. Another possibility is that with the increasing mechanization and increasing size of cultivation operations, fewer workers and separate operators will be needed. Thus, many nori fishermen will be moved into other types of employment.



In comparison to nori, cultivation of the brown alga, Undaria, is of relatively recent origin. The amount of wakame grown is still significantly less than nori, but is increasing rapidly from almost zero production in 1963 to over 60,000 tons in 1970. This exceeds the amount being harvested in Japan from natural beds. This alga, one of the Laminariales, is not native to American waters.

Culture Techniques

In the spring when the mature plants release the zoospores, "collector strings" are hung in the water on which the spores attach and the sporophytes grow. As with nori, this seeding now takes place in tanks although in the past it was done in the sea near natural beds. Also, past efforts to expand the beds have included creating new substrate surface by dropping rocks onto the bottom and exploding existing rocks with dynamite in areas with natural populations of Undaria. A wide variety of other techniques have been experimented on over the past 55 yr with some success (Tamura, 1966).

However, currently the collector string method is used in which the mature sporophylls are partially dried, placed into the tanks of fresh seawater and the released zoospores settle on a 100-m long string, previously wound around a vinyl plastic frame. The frame is removed after 1-2 hr and transferred to a l-m deep culture tank for the summer season. When the young plants reach about 1 mm in length (in the fall), the strings are transferred to rafts in the sea. The plants are harvested when they reach about 1 m in length.

Attempts to produce hybrids of three species of Undaria have met with some success, indicating that at least closely related species can be crossed (Saito, 1971).


If the strings are placed on the rafts before the water temperatures have dropped to 15°C, serious fouling can occur. Also, if the rafts are located in a rough water area and left floating on the surface, the young plants can be seriously damaged. In these areas the rafts can be anchored to a depth of 1 m to avoid this problem. Other problems which are not so easily remedied include some bacterial diseases and grazing of the young plants by isopods and gastropods. One last potential problem is the indication that production is increasing to the point of equalling, if not exceeding, the demand for wakame in Japan.



Many species of this genus are used by the Japanese as food; several of them being cultivated at the present time. While important as a food and as a source of alginic acid, kombu is still not in as great a demand as are nori and wakame.

Culture Techniques

The cultivation, dating back 250 yr, is quite different than that for nori and wakame. Kombu production is increased primarily through the improvement of available substrate and control of harmful "weeds" such as Phyllospadix, a marine spermatophyte. The latter is accomplished by dynamiting to clear the Phyllospadix from areas suitable for growth of Laminaria. The former involves the placing of additional large rocks on the seabed on which the plants may grow or, in some instances, using artificial substrate such as various shapes of concrete. In addition, some cultivation has been done using a hanging culture system (line and float).


Laminaria is one of the many valuable marine algae which have been plagued by the phenomenon called "iso-yake" by the Japanese which prevents the plant from adhering to the bottom. Apparently, the cause of this problem still has not been identified, but it usually occurs in areas where the bottom is covered with coralline algae. Some investigators have advanced the theory that this results in a "desert" condition with very little in the way of edible seaweeds available to shellfish in the area. Thus, if juvenile plants of Laminaria and other such algae begin to grow, they are grazed off rapidly.

In this same vein, the Japanese have determined, as we have in California, that abalone are found only where their primary source of food (brown algaekelps) is available (R. Burge, pers. comm.). In many areas, the brown algae are completely lacking and, thus, coastal waters in which abalone could grow, are not usable for cultivation. A very large-scale experiment is planned to begin in 1972 which will involve the establishment of a large kelp bed in a bay. If this is successful, 10 million abalone seed per year for 3 yr will be introduced into the kelp bed. This could lead to a new technique for expanding the capability of the Japanese for producing both Laminaria and abalone (Hisashi Kan-no, pers. comm.).

Other possibilities being researched include the development of techniques for cutting the normal 2-yr growth period to harvest down to 1 yr (Hasegawa, 1972). This has been accomplished and should lead to significant production increases.



Perhaps the most familiar algal extract to Americans because of its wide use as a component of bacterial growth media in both educational and medical facilities, agar is used for similar purposes in Japan. It is harvested for both domestic and export purposes, including sales in the United States. However, to meet the demand of the processors, Japan must now import about 5,500 tons of the 12,000 tons dry weight used in agar production.

Many red algae belonging to the families Gelidaceae and Gracilariaceae serve as the source of agar, but Gelidium is the most important genus in both Japan and the United States.

Culture Techniques

While much of the raw material for agar production is harvested from natural beds, some artifcial propagation is practiced and has been for about 300 yr. In the past, this has consisted largely of increasing the available substrate by throwing large rocks into the coastal waters in areas near existing beds where spores will be sufficiently abundant to seed the rocks. Other efforts to increase the supply of agarophytes have included mechanical cleaning of the rock surfaces, eliminating weeds (Ecklonia and Eisenia) from Gelidium beds, growing young plants to harvestable size attached to ropes hanging from floating lines, and, more recently, fertilizing the coastal water in which the algae are growing (Yamada, 1972). In this last effort, a lump of fertilizer (in the form of urea, ammonium sulfate, or a "nitrogen/phosphate mixture") is placed on the seafloor in the Gelidium bed and allowed to dissolve slowly. While this has succeeded on a commercial scale, the economic feasibility of this practice has not been fully demonstrated as yet.


Gelidium and its relatives are among the harvested seaweeds known to suffer from the iso-yake phenomenon. To date it has not been possible to control the release of spores from Gelidium as has been done with many other algae. Ability to do this would make the establishment of new populations much more certain. Another potential problem is Korea's growing production and export of agar which could create an excess and result in a profit loss for Japan.


Although the Japanese are still encountering many problems in optimizing the culture of the several species of marine algae, they are able to produce nearly as much as they need. Their real problems of the future appear to lie in the fields of l) undesirable pollution, 2) oversupply with its resultant lowering of price, and 3) idealizing the labor situation (improved working conditions, keeping wages and profits in line with other industries in Japan, keeping sufficient workers in the industry and finding acceptable employment for any excess over that which is needed, etc.).

Many of the techniques developed in Japan could be used by U.S. industry, but we face many problems which the Japanese do not. Our labor costs are already so high that nearly all seaweed farming in the United States would have to be essentially totally mechanized. Since the principal uses of seaweed in America are for nonfood purposes. the price paid for raw material will remain quite low. It is very doubtful that the public will allow the surface of our coastal water to be covered with a bambo-net type system used for Porphyra except in some very remote areas, such as in southeastern Alaska or on U.S. controlled islands.




1 Program Director. Office of Sea Grant. NOAA. Washington. D.C.20235

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