EN
The examinations were done on 40 cods fished at the Baltic sea during a scientific cruise of the „Profesor Siedlecki” boat. The level of specific antibodies against bacteria pathogenic for cods such as Vibrio sp., Aeromonas sp. and Pseudomonas sp. was determined by passive haemagglutination test using strains isolated from sick cods fished during the cruise and laboratory strains. Antibodies were found in 50% of sera of normal and 20% of sera of sick cods. The titre of antibodies was low, the highest titre was 1:16. Antibodies against Vibrio sp. were most prevalent. Less often were found antibodies against Pseudomonas sp. and Aeromonas sp.