considerable period of time during each tidal cycle. 

 Hardening results in an increased percentage of 

 survival, better growth rates, and less fouling. In 

 northern Japan, almost all commercial oyster seed 

 production takes place in Miyagi Prefecture. At 

 present, oyster seed production supplies not only 

 domestic uses, but also supplies some 30,000 to 

 50.000 cases of seed per year to the Pacific coast 

 of the United States and to parts of Europe, prin- 

 cipally France. 



Two met hods of hanging oysterculture are usually 

 practiced in southern Japan. In the first method, 

 seed oysters are transplanted to the rafts about 1 mo 

 after setting to grow: no hardening is done. These 

 oysters are harvested at the end of I yr. This method 

 is characterized by a short growing period and low 

 labor costs. In the second method, seed oysters are 

 hardened until autumn orearly winter. They are then 

 transferred to the rafts to grow and are not harvested 

 until the following year (known as 2-yr culture). 



The best oyster producing area in Japan is in the 

 Seto Inland Sea where calm conditions exist. Here 

 there are wide areas which enable the growers to use 

 large size rafts, 20 m long by 10 m wide. The Tohoku 

 region of northern Japan is also favorable for oyster 

 culture and longlines are used in some of the rough 

 water areas. It takes 2 yr for the oysters to grow to 

 market size. 



Oyster production is expected to remain stable 

 over the next few years. New species of oysters such 

 as the European flat oyster, Ostrea editlis. and the 

 Portuguese oyster, Crassostrea aniiiilata. may enter 

 commercial production in the future if the problem 

 of pollution along the coastal areas can be over- 

 come. 



SCALLOP CULTURE 



The aquaculture of scallops. Patinopecten yes- 

 soensis. has recently been developed in Japan. The 

 production of scallops on natural grounds has re- 

 mained poor during the past decade with annual 

 landings fluctuating between 5.000 and 15,000 tons. 

 Since the development of the hanging method for 

 catching seed and culturing scallops, production has 

 increased rapidly during the past few years and will 

 continue to do so. Because considerable quantities 

 of seed are being caught in Aomori and Hokkaido 

 areas of northern Japan, the scallop fishery is cur- 

 rently expanding. Ihe seed is not only beingcultured 

 in nets to market size but also released on the bottom 

 where good returns are being obtained 2 to 3 yr later. 



In 1969, 14.644 tons worth 1,833 million yen were 

 harvested from natural grounds and approximately 

 5,0(X) tons were produced from hanging culture. 



Seed scallops are caught in the spring. Several 

 kinds of cultch materials are used: vinyl fibre (used 

 gill net), vinyl film, branches of trees, etc. These are 

 suspended from rafts or longlines. Three months 

 after setting, the young scallops are transferred to 

 nets where they grow to 3-4 cm by autumn. The 

 culture of scallops can then go one of two ways: 

 Either the seed can continue to grow in nets for l'/2yr 

 to market size or they can be released on the natural 

 grounds. As high as an 809? return has been obtained 

 from released seed on the coastal area of Hokkaido. 



In the near future, a large-scale bottom farming of 

 scallops can be expected along the coast of Okhotsk 

 Sea, Hokkaido. This project will be made possible 

 because large amounts of scallop seed are available. 

 The site once produced 60,000 tons of scallops annu- 

 ally. To make the program successful, systematic 

 engineering and newly developed harvesting 

 machines such as suction dredges and underwater 

 bulldozers will be utilized. 



ABALONE CULTURE 



Considerable interest has developed in the cultur- 

 ing of abalone (Haliotis discus luinai in cold waters 

 and //. discus in warmer waters). These are very 

 important commercial species along the rocky sea 

 bottom both in quantity and quality. Production has 

 remained relatively stable over the past years as a 

 result of good management practices such as the 

 transplanting of natural sets to areas of poor setting. 

 In 1969, abalone landings totaled 6,463 tons valued 

 at 5,692 million yen (Table 1). 



Two approaches are planned in the aquaculture of 

 abalone — mass production of seeds in hatcheries 

 and the artificial production of food in the field by 

 seaweed afforestation. Artificial seed production 

 was developed in the 1960"s. Seed production is 

 expected to expand as studies are compjeted on the 

 conditioning of abalone for spawning and as com- 

 mercial hatcheries are developed. Good returns can 

 be expected from released seeds, 2-3 cm in shell 

 length, when they are harvested 3-4 yr later. 



There is a lack of knowledge about the food condi- 

 tions in the abalone's natural habitat. For this 

 reason, research was initiated in afforestation in the 

 field. .Afforestation could produce about 40 tons of 

 food that could feed up to 4 tons of abalone. The 

 seeds for this program will come from hatcheries. 



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