crops to recover when the planted nori become se- 

 verely damaged by disease or by some accident. 

 Nets with young buds are dried until the water con- 

 tent of the nori comes down to about 20-309f , are 

 packed in polyethylene bags, and are stored in re- 

 frigerators at about -20°C, in which buds can be 

 kept alive for more than 6 mo and capable of recover- 

 ing normal growth whenever they are returned to 

 sea. Even wet buds can endure the cold storage for a 

 short period, while many of the weeds and diatoms 

 are killed. Also a parasitic fungus, which often 

 causes disease on nori. loses its ability to reproduce 

 by this treatment. 



The number of nets with young buds stored in 

 refrigerators has increased in the past 5 yr. as shown 

 in Figure 1. This brought about new difficulties in 

 bud rearing, because cultivators have to rear the 

 buds with doubled amount of nets. In 1966-70, when 

 too many nets are set during bud rearing, these nets 

 often caused severe damage to the buds, resulting in 

 a sharp decline in harvest. This problem is now 

 solved by reducing the nets to a reasonable and 

 manageable amount on each ground. 



Techniques to expand nori grounds. -By using the 

 net collectors, nori culture has developed the 



c 



>- 2 



o = 



c Z 



O Q 



= 2 

 iQ < 



"" tn 



Z I- 

 O LlI 



F ^ 



O u. 



-I 



10 



9 



8 

 7 

 6 

 5 

 4 

 3 

 2 



NETS USED 



TOTAL SET 

 PRODUCTION 



C3/f^ 



1 



NETS 

 REFRIGERATED 



— FLOATING 

 SYSTEM 



— CLASSIC 

 SYSTEM 



I960 



1965 



1970 



Figure I. — Change inannualamount of "nori" production and in 

 the amount of cultivating sets and nets used. Generally a net is 

 spread in a set. 



grounds in the new areas after the old grounds were 

 destroyed by polluted waters and so on until 1965: 

 after that the development and loss came into bal- 

 ance. However, nori grounds are still showing an 

 overall increase by using a new rearing system, i.e.. 

 a floating-net system, which can make profitable 

 grounds out of waters of about 20 m deep and with 

 strong wave action. 



Generally a square frame of synthetic rope is set 

 floating on the surface of the sea with the help of 

 buoys and anchors, and 20 nets with small buoys can 

 be set in it. Waters with currents faster than 30 

 cm/sec or with somewhat strong wave action are 

 convenient for rearing nori by this system. The 

 frame systems can resist the impact of a wave 4 m in 

 height without any damage to nori. 



Mechanization of processes in nori culti- 

 vation. — Labor shortages and culture enlarge- 

 ment demanded the mechanization of each process 

 of production. It turns culture labor into a comfort- 

 able and profitable one. keeping the young labor force 

 from tlowing out into land industries. This is an 

 exception to the labor shortage situation for all 

 fisheries. For instance, oyster culture appears more 

 profitable in some localities than nori cultivation, but 

 labor in oyster culture is far more severe and dirty, 

 causing an outflow of young labor from the culture 

 industry. This loss of labor is making the culture fall 

 behind the nori cultivation. 



Introducing engineering principles to nuike or to 

 improve nori grounds. -From about 1965 engineering 

 principles have been introduced in nori cultivation. 

 For example, concrete or iron piles were set to de- 

 crease wave action in order to have nori culture 

 possible behind them. On the grounds in shallow 

 waters, water ways were dug to better the exchange 

 of water and to increase the harvest, and now in 

 several old grounds digging works are planned. Here 

 the connection between the biological and engineer- 

 ing techniques have to collaborate closely to make 

 the effort effective for production increment. 



Problems in Nori Cultivation 



The demand for nori by consumers, which is sup- 

 posed to increase year by year, was estimated at 

 about 5-6 billion sheets a year in 1970. The import of 

 nori from Korea is now politicallv limited to 200 

 million sheets a year, but it may increase to I billion 

 sheets in the future. Cultivation in Japan produced 6 

 billion sheets in 1970. satisfying the amount of con- 



11 



