It would be hard to overemphasize the importance 

 hybrid vigor will have in developing hatchery lines of 

 oysters, lobsters, scallops, fish and other marine 

 food animals, and algae. Hybrid vigor is so impor- 

 tant because, unless artificial seawater is used, water 

 pollution will always be a threat to the commercial 

 success of a hatchery. Because a hatchery must 

 carry its product through its most sensitive larval 

 stages, in smaller numbers than in the wild, and in 

 one spot as opposed to many in the wild, water 

 pollution can have a more disastrous effect in a 

 hatchery than in the field. 



Widespread use of artificial seawater would 

 necessitate the breeding of lines commercially pro- 

 ductive in such a media. Drastic changes in the 

 genotype would most probably be necessary. This is 

 not a genetic improbability by any means, but 

 aquaculturists do not give the idea much thought. 



LABORATORY VISITS 



Even though there has been no general, broad 

 program of fish or aquacultural genetics in Japan, 

 some fine genetic research has gone on in various 

 fishery laboratories. This work has not yet had a 

 great deal of impact on the general fisheries. It is 

 related here along with comments and discussions 

 regarding aquaculture-related genetics. The re- 

 search cited is a sampling of the sort of work that will 

 most likely be conducted in the future on a larger 

 scale. 



Oyster Research Institute at Kesen-numa on 

 Mohne Bay — Oyster, Scallop, and Abalone 



The Oyster Research institute at Kesen-numa 

 (chief researchers now H. Kan-no and T. Seki) de- 

 veloped, under the leadership of T. Imai, methods 

 for the artificial rearing of the Japanese oyster, C. 

 f;if>a.s. This Japanese work paralleled the prior work 

 of Loosanoffand Davis (1963) of the Milford Biolog- 

 ical Laboratory, now part of the National Marine 

 Fisheries Service. From the Kesen-numa Labora- 

 tory also came a breeding study on C. fiii^'us, which 

 included the effects of inbreeding, hybridization be- 

 tween members of different geographic races, and 

 interspecies crosses using the Japanese oyster as one 

 of the species parents (Imai and Sakai, 1961). Addi- 

 tional aquaculture and breeding information is con- 

 tained in a recent book edited by Imai et at., 1971, 

 "Through culture in shallow seas (progress in shal- 

 low seas culture)." This book is now being trans- 



lated from the Japanese through the auspices of the 

 National Oceanic and Atmospheric Administration. 

 At least for some considerable period of time adult, 

 fertile hybrids of the cross C. gigas x C. angulata 

 were maintained at the Kesen-numa Laboratory. 



This Institute is now rearing the European oyster, 

 Ostrea ediilis. which does well in Japan as a hatchery 

 species. These oysters are sold as spat to growers 

 and marketed. C. angiiUita is also being reared. No 

 genetic studies are now being conducted on the oys- 

 ter. 



The sea scallop, Patinopecten, is also being 

 raised. The scallop fishery still depends on the cap- 

 ture of juveniles, not on hatchery rearing. However, 

 at least in Mutsu Bay annual catches of P. yessoensis 

 fluctuate widely. This is attributed to a natural insta- 

 bility of the reproduction of this species. Natural 

 reproductive instability would make this scallop an 

 excellent candidate for reproduction in the hatchery. 

 Some of the scallops are known to be functional 

 hermaphrodites. Use could so be made, for both 

 experimental and commercial breeding work, of 

 their rapid inbreeding potential by self-crossing. 



Research at the Kesen-numa Laboratory is now 

 concentrating on the abalone. The market for this 

 marine gastropod is excellent, and there is an urgent 

 need to mass produce the young. Unlike the situa- 

 tion for the oyster and scallop, mass collection of 

 wild abalone is fairly difficult. Young abalone escape 

 from the collectors, and in their natural habitat, they 

 shelter themselves under boulders or rocks. To in- 

 crease production it is, therefore, essential to pro- 

 duce the young artificially. 



In Japan 10 species of abalone are found. Only 

 four of these species constitute the staple food 

 products — HuHutis haliotis discus hannoi, H . dis- 

 cus, H. sieboldii, and//, gigantea. Of the total catch 

 H . discus hannoi supplies 58%. 



At present, no genetic studies on abalone are 

 being conducted at Kesen-numa. However, there is 

 interest in possible genetic causes of the less than 

 desired percent survival of the young larvae, in the 

 chromosomes of the abalone, and in genetic resis- 

 tance to disease. Disease is anticipated as a potential 

 serious problem in the very intensive system under 

 which the abalone will be reared. The intensive sys- 

 tem includes a period of growth in the heated waters 

 of a nearby power plant at Shiogama. An above- 

 ground running water tank system contains the 

 abalone at this time, and a hatchery with experimen- 

 tal facilities has been built at the power plant near the 

 tank farm. 



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