Abstract: Abstrac:To elucidate the relationship between " Cryptocaryoniasis" caused by Cryptocaryon irritans infection and secondary bacterial infections in Trachinotus ovatus, this study conducted continuous sampling of naturally infected fish in offshore deep-sea cage farming systems and laboratory-reared individuals. Artificial infection experiments with C. irritans were performed to investigate the correlation between infection intensity of the parasite, secondary bacterial infection rates, hepatic bacterial loads, and to identify dominant bacteria in the livers of diseased fish. The results demonstrated that both secondary bacterial infection rates and hepatic bacterial loads significantly increased with the severity of C. irritans infection. Spearman correlation analysis revealed a positive correlation between secondary bacterial infection rates, hepatic bacterial loads, and the clinical severity of cryptoglandular disease (P < 0.01). Peak secondary bacterial infection rates and hepatic bacterial loads were observed at 120 h and 168 h post-C. irritans infection. Among 93 dominant bacterial strains isolated from liver tissues of farmed T. ovatus in the natural marine environment, Photobacterium damselae subsp. Piscicida and Vibrio harveyi were identified as predominant pathogens. This study provides a theoretical basis for the prevention and treatment of C. irritans infection and its associated secondary bacterial infections.