supplied to all farms in the country from 28,363.000 

 to 30.780,000 per year (Harada, 1970). 



The young yellowtail are reared in small net en- 

 closures for 1-2 mo until they reach a length of 25-40 

 mm. These seedlings are then placed in larger float- 

 ing net cages approximately 6 x 6 x 2 m in which 

 1, 500-2. .SOO fish can be kept. By December the yel- 

 lowtail reach a size of 1 .0-1 .5 kg and are shipped to 

 market. 



In southern Japan where the minimum tempera- 

 ture exceeds ITC, it is possible to hold yellowtail 

 through the winter and sell them in April when they 

 reach a weight of 2-3 kg. but winter temperatures 

 farther north are too low for yellowtail. According to 

 Fujiya (1969), about 95% of the yellowtail are ship- 

 ped to market by December. Detailed descriptions 

 of yellowtail farming procedures are included in 

 papers by Harada ( 1970), Furukawa (1970). and Fu- 

 jiya (1969). 



Problems of the industry include 1 ) a stable supply 

 of seedlings. 2) disease control, and 3) adequate food 

 supply or development of suitable artificial diets. 



1 )Stahli' supply ofscedliniis. Production from yel- 

 lowtail farming is limited to approximately the pres- 

 ent level because of government restriction on the 

 number of young fish which can be taken from 

 coastal waters. According to Harada (1965), it is 

 highly desirable to produce seedling yellowtail by 

 artificial fertilization in a hatchery. This has been 

 accomplished recently on an experimental basis, but 

 has not been perfected for commercial application. 

 In the meantime. Harada recommends collecting the 

 seed (larval or juvenile fish) at as early a stage as 

 possible and keeping them under careful manage- 

 ment to reduce mortalities. 



Although production could be increased by im- 

 proving growth rate, reducing mortality, or by ex- 

 tending the rearing time in places where winter water 

 temperatures are not too low. ultimate development 

 of the industry will require maintenance of a spawn- 

 ing stock, collection and hatching of eggs, and rear- 

 ing of larval stages to assure a dependable supply of 

 seedlings. 



2) Disease control. The monogenetic trematode. 

 Beneclenia seriolae. infects the skin of the yellowtail 

 causing an unsightly appearance, loss of appetite, 

 weakening or death of the fish. This parasite is con- 

 siderably less resistant to low specific gravity than 

 the host fish and consequently is easily controlled by 

 dipping the infected fish in fresh water for a few 

 minutes and then returning it to seawater. The time 



of dipping must be shorter in the summer (3 min at 

 26X ) than in the autumn (5 min at 16°C) to prevent 

 damage to the fish. Since this parasite grows very 

 fast and becomes adult within 2 or 3 wk. the freshwa- 

 ter treatment must be repeated frequently during 

 periods of infection. 



Another monogenetic trematode. Av/'/ic iHeter- 

 axine) helerocercd. infects the gills of yellowtail 

 causing anemia which may kill the fish. Treatments, 

 according to Fujiya (1969). include 4-min bath in 

 water containing 4% salt. 2) dipping in a 1% solution 

 of "Tremaclean"" for 30 sec, and 3) oral treatment 

 by including "Bitin"" (4,5-dichlorophenol) in the 

 food. 



The bacteria Vibrio can cause extensive infections 

 in yellowtail populations. Treatments include incor- 

 poration of sulfa drugs or antibiotics in the food. 



Virus diseases are suspected, but no information 

 is available concerning these. 



The feeding of oxidized, unsaturated fatty acids 

 contained in fish used as food causes nutritional 

 diseases of yellowtail. This can be prevented by 

 feeding white-meated fish instead of anchovy, mack- 

 erel, and sand lance. 



3)Adeqiuitefo()cl supply or development of artifi- 

 cial diet. Farming of yellowtail in Japan depends on 

 availability of large quantities of cheap fish suitable 

 for use as food. These include mackerel, horse mack- 

 erel, anchovy, sand lance, and saury. With conver- 

 sion rates of 6: 1 to 8:1 the food must be obtained at 

 very low price in order to make yellowtail farming 

 economical. Expansion of the industry or perhaps 

 even continuation at the present level will require 

 development of artificial diets which will provide 

 better nutrition for the fish and reduce dietary dis- 

 ease problems. Furthermore, the artificial diet must 

 be available at a price which will permit economic 

 fish farming. 



PUFFER CULTURE 



Puffers, also known as globefish or blow fish of the 

 genus Filial, are in high demand as a luxury food in 

 Japan even though certain species are extremely 

 toxic. About 10 species of edible puffers occur in 

 Japan, but one species. Fuiiti ruhripes nihripes. is 

 used principally for farming ventures. The toxicity 

 of puffers changes seasonally, becoming the greatest 

 in the spawning season from May through June. The 

 toxic substance "Tetradotoxin" occurs mostly in 

 the ovary, liver, intestines and skin, and rarely in the 

 muscle. When prepared carefully by licensed cooks 



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