Marine tenacibaculosis is a severe bacterial disease distressing a great variety of marine fish especially cultured species. Both adult and young are liable but the young fish are being affected that too severly. The filamentous organism Tenacibaculum maritimum (formerly FLexibacter maritimus) is the causing agent of ‘marine flexibacteriosis’, which is affecting cultured marine fish in Japan and Europe. Since fish farming is becoming a progressively growing industry, outbursts of tenacibaculosis have arisen everywhere in the world. It had been recorded in Japanese stumble, Paralichthys olivaceous and yellowtail Seriola quinqueradiata and other fishes in Japan.