クロダイ仔稚魚のいわゆる腹部膨満症に関する細菌学的研究

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Mass mortalities had been frequently occurring in the early stage of development of hatched black sea bream Acanthopagrus schlegeli at hatcheries in west Japan. Normal, morbid and dead fish were collected at three, six and fourteen days after hatching at Kochi Prefectural Fish Farming Center during the period from April to June 1984. After homogenation of these fish, total number of bacteria and bacterial flora were determinded. Number of total bacteria was about ten times greater in morbid fish than in normal fish after an outbreak of the disease. Three species, Vibrio alginolyticus, Vibrio nereis, and Alcaligenes Cupidus were found dominant in the bacterial flora of morbid fish. Using waterbone infection and oral infection by feeding rotifer, Brachianious plicalitis artificially infected with these microorganisms, V. alginolyticus and A. cupidus gave high mortality in norsmal fish but not V. nereis. The results indicate that V. alginolyticus and A. cupidus may cause the mass mortality in black sea bream fry.