2020 Volume 55 Issue 2 Pages 42-45
Flavobacterium psychrophilum, which causes bacterial cold-water disease, was detected in the ovarian fluid of female chum salmon used for mating in a hatchery in Iwate Prefecture in 2018. The detection rate of F. psychrophilium in chum salmon was 0.0–91.7% in individuals captured from a river; 0.0–100.0% in individuals captured from the sea and stocked in fresh water before testing; and 21.4% in individuals captured from the sea and not stocked in fresh water. Pre-water-hardening disinfection of fertilized eggs was performed for 21,165 thousand eggs in the hatchery, where the average eyed-egg ratio was 92.4%. Intra-ovum infection was not detected in the disinfected eggs, but 23.3% of non-disinfected eggs became infected.
