Four new species of Ceratomyxa were found during parasitological studies of fish caught in shallow areas of Peter the Great Bay, Russia. Two of them (C. aspera n. sp. and C. durusa n. sp.) were found in the gall bladders of the flounders Limanda aspera and L. herzensteini. The third species (C. azonusi n. sp.) infected the gall bladder of the greenling Pleurogrammus azonus, and the fourth (C. lianoides n. sp.) was found in the gall bladder of Stichaeus grigorjewi. Ceratomyxa spp. have not been previously described from P. azonus or S. grigorjewi.