However, with increase in population, shortages 

 in the supply of wiki wakame occurred in the 1960's, 

 stimulating the development of its cultivation. A 

 new product, salted wakame, was developed and 

 welcomed by consumers for convenience in cook- 

 ing, and this product did a great deal for increasing 

 consumption. 



Under these circumstances wakame cultivation 

 had an abrupt growth mainly in northern districts of 

 Japan. The annual production was almost zero in 

 1963 and was over 60,000 tons in 1970, which ex- 

 ceeds the harvest from natural beds. 



Processes in Cultivation 



At the end of the season, wakame becomes mature 

 and develops zoospores, at the time fishermen start 

 to prepare the "seed strings"" for the next season. 



For collecting spores, strings of 2-3 mm in diame- 

 ter made of synthetic fiber are used. The 100-m long 

 strings are reeled over a frame made of vinyl plastic 

 tube of 2-3 cm in diameter. A tank is filled with fresh 

 seawater. Mature sporophylls of wakame are put 

 into the tank after half drying. Enormous numbers of 

 spores are released into waters, when the vinyl 

 frames with strings are set in the tank so as to catch 

 the spores. Several sporophylls are necessary for 

 seeding a 100-m string. After 1-2 hr the frames are 

 taken out and are put into culture tanks of about 1 m 

 deep, where they are kept through the summer under 

 controlled light intensity. It is desirable to keep the 

 water temperature lower than 25°C. Favorable light 

 intensity over them is 500 lux at 25°C and 1 ,000 lux at 

 20°C. 



Germlings of wakame develop in the fall when the 

 water temperature goes below 20°C. When young 

 buds grow to about 1 mm in length, the frames with 

 strings are put into the sea hanging from a raft, so as 

 to accelerate their growth. 



In northern waters, where invasion of fouling 

 seaweeds and animals is less, the seeded strings are 

 often cultured in the sea. 



Management and Harvesting 



The cultivation starts when the seawater tempera- 

 ture becomes 15°C and fouling organisms become 

 scarce. A synthetic rope of 100 m long and of 8-10 

 mm in diameter is floated into the sea with the help of 

 buoys and anchors. Often many branch ropes are 

 hung from the rope. Seed strings with young buds of 

 wakame are rolled up to the rope. Sometimes seed 

 strings are attached to the ropes at 10-cm intervals 

 after being cut into pieces of about 10 cm long. 



In waters which are too rough or with many float- 

 ing 5«/\i,'flii///?( plants, the rope is set at a depth of 1 

 m, where the buds can escape being damaged by 

 wave action or by rubbing off by Sciif^a^siiiu. 



Wakame grows quickly in winter. The optimum 

 temperature for its growth may be about IO°C. The 

 longer the period of lower than 15°C, the greater the 

 harvest. However, temperatures lower than 5°C 

 may injure the plant and may decrease the crop. Fast 

 current and strong wave action are favorable for 

 growth of the alga, if they do not damage the cultiva- 

 tion set. 



Harvest is done by cutting the weed which has 

 grown to about 1 m in length. Most of it is dried under 

 the sun or in a drier. Some of it is sold raw to meet 

 local demands. The yield from 1 m of cultivating 

 rope in a season is about 10 kg in wet weight in the 

 northern areas and about 5 kg in warmer districts. 



The amount of labor work in wakame cultivation 

 is far less than that in nori cultivation. The set of the 

 former is more resistant against rough waves than 

 that of the latter. For these conditions the former is 

 more profitable in northern open coast than the lat- 

 ter. However, the amount of consumption is now 

 limiting progress of the industry. 



With the spreading of the cultivation, new prob- 

 lems are occurring, i.e. , damages caused by bacterial 

 diseases and by the eating of young buds by isopods 

 and gastropods. 



Harvest of Wild Wakame 



The amount of production changes every year 

 primarily because of the variations in water tempera- 

 ture. The low temperature in the growing season, 

 winter to spring, brings about a good crop except at 

 the north limit. 



Elimination of harmful seaweeds in wakame beds 

 is found to be effective in increasing production dur- 

 ing the season. The bed is likely to be taken over by 

 other perennial weeds, Phyllospadix in the north and 

 Sargassiim and Ecklonia in the south. The best time 

 to control the weeds may be during the germinating 

 season of wakame buds. 



We have never produced a favorite culture area by 

 throwing stones into the sea. which is effective in the 

 case of Laminaria and Gelidium. Limiting the 

 amount of the harvest and transplanting mature 

 plants were found ineffective for producing a better 

 crop the following year. 



Wakame is an annual plant and there is an enorm- 

 ous mortality in the microscopic phase in the sum- 

 mer. These conditions may cause the ineffectiveness 



13 



