SHELLFISH CULTURE IN JAPAN 



WILLIAM N. SHAW 



INTRODUCTION 



Japan has long been recognized as a leader in the 

 aquaculture of molluscs. In 1969, approximately 

 560,000 tons (with shell) of shellfish were harvested 

 (Japanese Fisheries Association, 1971). Principal 

 species under cultivation include Pacific oysters, 

 Crassostrea gigas, scallops, Patinopecten yessoen- 

 sis. and the abalone, Haliotis discus. Several species 

 of clams and snails also play an important role in the 

 total production figures, but these are mostly caught 

 from wild populations and are not farmed to any 

 extent. 



During my short tour of aquaculture sites in Ja- 

 pan related to the UJNR (United States-Japan Nat- 

 ural Resources) Aquaculture Panel, I concentrated 

 my effort on surveying the areas where oysters, 

 abalone, and scallops are being farmed. An over- 

 view based on these visits is listed below. 



OYSTERS 



Oyster production in Japan has shown a steady 

 increase in recent years. From 1958 to 1968, landings 

 rose from 151,894 tons (with shells) to 265,881 tons 

 (Furukawa. 1971). Production declined slightly in 

 1969 when 245.000 tons were harvested (Japanese 

 Fisheries Association, 1971). 



A major reason for the increase in production is 

 the expansion of the hanging method of oyster cul- 

 ture, raft, longline, and rack. By using the third 

 dimension, the yield per acre is greatly increased 

 over the bottom or sowing method. Furukawa (1971) 

 estimates that the oyster yield from raft culture in the 

 Hiroshima Prefecture is 20 tons of oyster meats per 

 acre per year. These figures compare favorably with 

 Ryther and Bardach's ( 1968) estimate of 23.3 tons 

 per acre per year. 



The entire industry is dependent on the natural 



' Middle Atlantic Coastal Fisheries Center. National Marine 

 Fisheries Service. NO.A.A. Oxford. MD 21654. 



production of seed oysters. Both scallop shells 

 (northern and southern variety) and oyster shells are 

 used for cultch. Shells are strung on wires ('/2-inch 

 bamboo spacers are used to separate scallop shells) 

 and draped over racks. Following setting, the seed 

 caught on scallop shells is used domestically while a 

 considerable portion on oyster shells is exported to 

 the United States and France. 



Twomajorareasofoysterproduction were visited 

 during the tour — Miyagiand Hiroshima Prefectures. 

 In addition, we visited Lake Hamana, the only 

 saltwater lake in Japan, where shallowwater rack 

 culture is being carried out. 



According to Furukawa (1971), Miyagi Prefecture 

 produced 3,814 tons ofoyster meats in 1968,orabout 

 9.3% of the total Japanese production. Matsushima 

 Bay has been one of the most important culture areas 

 in Miyagi Prefecture. In 1959, 1,456 tons of shelled 

 oysters were harvested. However, beginning in 1961 

 mass mortalities occurred in Matsushima Bay. Total 

 annual losses from 1961 to 1964 were 62. 5, 41. 6, 42. 3, 

 and 51.9%, respectively (Kan-no et al., 1965). 



From our on-site visit of Matsushima Bay, it was 

 apparent that the Japanese had solved their oyster 

 mortality problems by converting the Bay's use from 

 oyster culture to seaweed culture. Very little oyster 

 culture in the Bay proper was observed. 



Yet, total oyster production for Miyagi Prefecture 

 has declined only slightly. The Japanese have ex- 

 panded raft and longline culture in areas outside 

 Matsushima Bay. 



One big industry in the Miyagi Prefecture is the 

 exportation of seed oysters. On our tour, we had the 

 opportunity to visit this operation at Watanoha 

 as they were preparing seed for air shipment to 

 France. Oyster seed, which is hardened on racks 

 for 3 mo, is brought ashore in small boats. The 

 seed (all caught on oyster shells) is removed from 

 the galvanized wire strings, placed in baskets, 

 and thoroughly washed. It is then culled into 

 single pieces and examined for predators; all shells 

 with six or less sp^t are discarded. The good shells 



107 



