prawns are protected for a certain period and re- 

 leased after adapting them to natural water, 5 to 10% 

 of the released numbers can be harvested. 



As a result of this program, prawn has been pro- 

 duced on a commercial scale. Also red sea bream, 

 octopuses, globefish, scorpionfish, sea-eel. blue 

 crab, and abalone. The prawn project is emerging 

 from its experimental to a semibusiness stage. 



The prawn commonly cultured in Japan is Pen- 

 aeiis juponiciis. It is one of the most expensive of 

 seafoods in Japan. Artificial culture techniques for 

 this species have been developed over the last 10 yr 

 by fisheries biologists and professional aquacul- 

 turists. Despite a number of technical and 

 socioeconomic difficulties in the commercial pro- 

 duction of prawn in Japan, it is evident to the 

 Japanese that an increasing demand for prawn and 

 shrimp will stimulate the development of its culture 

 as an industry wherever in the world it is at all 

 feasible. Culture should be particularly promoted in 

 the untouched, widely ranging swamplands in the 

 tropical zones. However, presently in Japan, poor 

 culture techniques, defects in the present system of 

 intensive culture, laborious rearing operations, ris- 

 ing land costs, and unfavorable rearing conditions 

 owing to pollution make for unstable and costly pro- 

 duction on prawn farms. A decrease in artificial pro- 

 duction is anticipated. Culturists wonder whether 

 prawn farms can even be maintained in Japan in 

 competition with more productive enterprises. Yet, 

 an overwhelming demand continues to exceed pro- 

 duction even though at the Tokyo Central Fish Mar- 

 ket a kilogram of live prawn has been sold for as 

 much as 8 to 30 U.S. dollars (Second International 

 Ocean Development Conference, 1972). 



The prawn fishery.justasthe shrimp fishery in the 

 United States, might well be the fishery that would 

 benefit monetarily most quickly from a well- 

 integrated, sensibly supported genetics program. 



Experimental studies on the hybridization of the 

 freshwater shrimp are being carried on at the Tokyo 

 Fisheries University (Uno and Fujita, 1972). Cross- 

 es of Macrohracliiiim nippoiiense Q x M. for- 

 luoscnsc -i" and reciprocal crosses were reared 

 from the larval stage to sexual maturity. Morpholog- 

 ical comparisons of hybrids to each parent were 

 made. These interspecies crosses were achieved by 

 exposing the excised spermatophores to 50% seawa- 

 ter for 15 to 30 min. and then attaching them to the 

 ventral thoracic part of the female of the other 

 species just before she spawned. Such hybrids could 

 have advantages over nonhybrids for intensive 



aquaculture under artificial conditions, or for "col- 

 onization" of a new area in the wild. 



POLLUTION AND INTENSIVE AQUACULTURE 

 WITH "SEMIDOMESTICATED " STRAINS 



Possibly, even before breed improvement, with 

 concomitant genetic adaptation to the cultivated 

 state, aquaculture of some ""semidomesticated" 

 forms will become a success with the disappearance 

 of their wild progenitors from Japan's coastal wa- 

 ters, or when these wild forms accumulate enough 

 contaminants to become unfit for human consump- 

 tion. Oyster seed production has been eliminated 

 from around the City of Hiroshima with implications 

 for the entire fishery. Yet. while pollution of wild 

 stocks and their demise by marine contaminants may 

 make some aspects of commercial hatchery produc- 

 tion more attractive, too widespread pollution would 

 render even artificial production in natural seawater 

 virtually impractical. The Japanese regard the future 

 success of artificial culture to be intimately tied to a 

 resolution of pollution problems. 



APPLIED AND BASIC GENETIC RESEARCH 

 TO SUPPORT FISH BREEDING 



For many years Japan has emphasized applied 

 research in the fishing fields. A system of extension 

 services for the fisheries is well established. In the 

 United States the Sea Grant Program stresses ap- 

 plied research and extension services, but Japan is 

 looking in the opposite direction. Unlike the Ameri- 

 cans, the Japanese have made near maximum and 

 efficient use of applied research. Now, Japanese 

 scientists actually carrying out the work and their 

 research administrators alike are of the opinion that, 

 to increase further the productivity of their fisheries, 

 more basic research is required. In the past, such 

 research has been largely confined to universities 

 where it has not been well funded and to special 

 national institutes. Basic research, they believe, is 

 necessary to develop reliable means of carrying reg- 

 ularly large numbers offish from egg through sexual 

 maturity, and this in the face of serious pollution. 

 Such work should be deliberateh associated with 

 breed improvement programs, and the Japanese 

 recognize this. Even if the\ did not. some useful 

 genetic selection would occur inadvertently. 



Food and disease appear to be presently regarded 

 as more important constraints on aquaculture gener- 

 ally than lack of special breeds. However, the 



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