batch. As a control, eight scallops were immersed into a seawater suspension of 105 R. salmoninarum cells per ml for 4 h and then were cultured for 30 days in an aquarium at Kitasato University. Two scallops were examined after 2 days and the other scallops were examined 30 days later for the presence of R. salmoninarum. R. salmoninarum antigen could be detected by IFAT and IDBA using polyclonal antibody from six samples of flathead and one of Japanese sculpin (Table 1). In the case of monoclonal antibody, the same samples were also positive for R. salmoninarum. However, these antigen-positive fish did not show any signs of BKD. R. salmoninarum antigen was not detected in the kidneys of flounder or greenling. No bacteria were isolated on SKDM, nor were R. salmoninarum cells observed by Gram staining. Isolation of R. salmoninarum from the seawater was attempted, and several colonies grew on SKDM from each batch. However, by the Gram stain and serum agglutinating test, no colonies were identified as R. salmoninarum. The R. salmoninarum antigen was detected, by IFAT and IDBA using the polyclonal antibody, in the midgut gland of 31 samples of scallops (Table 2). With the monoclonal antibody, 25 samples of 31 R. salmoninarum polyclonal antibody-positive samples showed a positive reaction by the IFAT and the IDBA. Thus, R. salmoninarum antigen was detected in 25 of 86 scallops examined. R. salmoninarum isolation from these scallops was also attempted; however, no bacteria identified as R. salmoninarum grew. BKD infection is limited to salmonids, although lamprey (Lampetra tridentata) (4), carp (Cyprinus carpio) (12), and sablefish (Anoplopoma fimbria) (3) have been experimentally infected with R. salmoninarum. Sablefish became moribund or died of apparently incomplete infections of R. salmoninarum within 50 to 71 days. We detected R. salmo