河川における冷水病菌をめぐる在来魚と放流アユとの関係  [in Japanese] Relationships of the infectivity of Flavobacterium psychrophilum between native fishes and released ayu Plecoglossus altivelis in a river  [in Japanese]

アユ放流前(2月)の河川においてオイカワに発生した冷水病の原因菌をめぐる在来魚種と放流アユとの同所的動的関係を冷水病菌のPCR-RFLP型を識別手段として4月から6月まで追跡した。オイカワの冷水病菌(BS型)は,アユ放流後の5月下旬までオイカワにのみ保菌されていた。一方,アユでは冷水病の発症,保菌が6月下旬まで確認されたが,BS型は検出されなかった。オイカワとアユの冷水病菌の間には宿主をめぐって一定の隔離があることと,室内実験からも冷水病菌の宿主に対する感受性に違いがあることが明らかになった。

To clarify the dynamics of the infectivity of Flavobacterium psychrophilum between wild fishes and released ayu, PCR-RFLP analyses of F. psychrophilum isolated from wild fishes collected in the Kako River from April to June were performed. F. psychrophilum (BS type) isolated from pale chub was killed by the cold water disease in February, before the release of landlocked ayu of Biwako, and was isolated only from pale chub until late May. 0n the contrary in ayu, although an outbreak of the cold water disease was confirmed by late June, the BS type of F. psychrophilum was not detected. It was clarified that there were different strains of F. psychrophilum infecting pale chub and ayu. It was confirmed that there were differences also in the sensitivity of hosts from the challenge test in the laboratory.