Investigation of Disease Outbreak Trends through Monitoring of Olive Flounder Paralichthys olivaceus in Jeju Island

Olive flounder (Paralichthys olivaceus) is a major aquaculture species in Korea, with over 50% of the total production is produced in Jeju. To investigate the disease outbreak trends in olive flounder aquaculture farms on Jeju Island, monitoring was conducted from May 2022 to December 2023. A total of 2,168 olive flounder were collected, and the detection and infection trends of disease outbreak were analyzed. A total of 1,057 cases involving four bacterial species, 1,073 cases involving five parasitic species, and 98 cases involving two viral species were identified and detected. The dominant pathogens detected were scuticociliates, Trichodina spp., two myxosporean species (Enteromyxum leei, Pavicapsula anisocaudata), Tenacibaculum maritimum, and Streptococcus spp. Among them, most pathogens, except for T. maritimum, Edwardsiella piscicida., and E. leei, did not show clear seasonality and were detected year-round. The study found that single infections had a higher prevalence compared to co-infections.