Detection of Aeromonas salmonicida in the coelomic fluid and kidney of mature chum salmon (Oncorhynchus keta), pink salmon (O. gorbuscha) and masu salmon (O. masou).

Abstract

Detection survey on Aeromonas salmonicida was conducted from the coelomic fluid of 420 mature chum (Oncorhynchus keta), 120 pink (O. gorbuscha), and 180 masu (.O. masou) salmon which have no clinical signs of furunculosis, in 1989 in Hokkaido. A. salmonicida was isolated from 22 out of 120 chum salmon from the Tokachi River. The number of A. salmonicida in the coelomic fluid ranged from 10¹ to 10⁶ CFU/ml in the samples from Shibetsu and Teshio rivers, respectively. It is suspected that the coelomic fluid contaminated with A. salmonicida flows out from the fish at the time of stripping eggs or during maturation in the pond. Since most hatcheries in Hokkaido drain untreated sewage directly to rivers, A. salmonicida in the coelomic fluid from mature fish may contaminate the river water and infect other anadromous salmon with A. salmonicida.