Interferon regulatory factors (IRFs) play crucial roles in antiviral processes, such as in the transcriptional induction of interferon (IFN) and IFN-stimulated genes (ISGs). In this study, the genes encoding IRF5 and IRF6 were identified in Pagrus major, and their expression in various organs after pathogen infection was analyzed. In the coding sequences of P. major (Pm)IRF5 and PmIRF6, the DNA binding domain, IRF association domain, and viral-activated domain were found to be highly conserved. Phylogenetic analysis revealed that PmIRF5 and PmIRF6 were most closely related to IRF5 and IRF6 of large yellow croakers. The mRNAs for PmIRF5 and PmIRF6 were constitutively expressed in all organs analyzed but were highly expressed in the liver and gills. As a result of an infection with red sea bream iridovirus, a major pathogen of red sea bream, PmIRF5 and PmIRF6 expression was significantly upregulated in the spleen and kidney. On the basis of these results, it can be concluded that IRF5 and IRF6 expression play an influential role in the immune system of red sea bream infected with viruses.

Emaciation disease has directly affected the production of olive flounder—a major aquaculture species in Korea—since the 2000s. Various myxosporeans have been reported as its causative agents. In this study, we investigated the recent resurgence of emaciation on Jeju Island, considering not only myxosporean infections but also potential environmental factors. Unlike previous studies that have primarily attributed the causes of emaciation disease to infections by myxosporeans, this research aimed to determine whether pathogen infection is indeed the sole cause of emaciation disease through molecular and histopathological analyses. Molecular biological and histopathological analyses of aquaculture and laboratory samples revealed that gross pathology lesions of emaciation can occur in the absence of pathogens, as well as in environments with myxosporean infections. These findings suggest that emaciation disease can be exacerbated by certain environmental factors in addition to myxosporeans. Future research should focus on detailed experimental designs to identify the specific environmental conditions contributing to the severity of this disease.

Suspended solids are small particles transported in the water column, which can damage marine ecosystems and impair the health of aquatic organisms. This study evaluated the physiological responses of clams (Venerupis philippinarum) and Atlantic Bay scallops (Argopecten irradians) to suspended solid exposure. Four concentrations (100–1000 mg/L) were tested, with a control group maintained at 0 mg/L. At each time point (1, 2, 4, 6, 8, and 12 days), hemolymph samples were collected from five individuals per group to measure GOT, GPT, ALP, and cortisol. Exposure to suspended solids significantly increased these biochemical indicators compared with the control. Quantitative survival analysis showed that Venerupis philippinarum survival declined to 83.3% (25/30) at 500 mg/L and 76.7% (23/30) at 1000 mg/L after 5 days, while the control maintained 100% survival. In Argopecten irradians, survival remained close to 100% in most treatments, with a slight reduction to 83.3% (25/30) at 1000 mg/L. No mortality occurred in the control group without suspended solids, whereas mortality was evident under combined temperature stress and suspended solid exposure. These findings demonstrate that suspended solids induce stress responses in both species, with early mortality in Venerupis philippinarum likely caused by particle adhesion to the gills, leading to reduced respiratory efficiency.

Coastal sea-cage aquaculture environments support dynamic microbial communities, yet their viral components remain poorly characterized. This study profiled DNA viral-like reads recovered from total metagenomes of iron-flocculated seawater concentrates (operationally termed DNA virome) at a rock bream (Oplegnathus fasciatus) sea-cage farm off Geoje Island, Korea, at five time points between July 2024 and May 2025 using long-read Nanopore metagenomics. Multivariate analyses of DNA virome composition indicated temporal patterning in virome composition; samples collected within the cages tended to group together. The DNA virome was dominated overall by bacteriophages of abundant marine bacteria and by viruses infecting picoeukaryotic phytoplankton, and it showed marked temporal turnover during the investigated year: Micromonas-associated viruses became prominent in December, whereas Ostreococcus- and Bathycoccus-associated viruses increased during seasonal rewarming in May, suggesting that environmentally driven changes in microbial host communities may contribute to temporal virome turnover. Pelagibacter phage abundance was positively correlated with that of its potential host Pelagibacter ubique, and both Synechococcus T7-like virus and Synechococcus virus were positively correlated with Parasynechococcus marenigrum, associations that are consistent with, but do not demonstrate, taxon-specific virus–host relationships. Nanopore reads assigned to infectious spleen and kidney necrosis virus, now classified within the species Megalocytivirus pagrus 1, were recovered from samples collected in September 2024 (12,960 bp) and May 2025 (340 bp). Average nucleotide identity analysis indicated that the seawater-derived sequence was most closely related to red seabream iridovirus subtype II, the subtype predominant in Korean cultured marine fish. The seawater virome results and the bioinformatic pipelines developed in this study together may provide a non-invasive approach for tracking temporal virome dynamics and for environmental screening of viral pathogen DNA in sea-cage aquaculture.

Surgical techniques are gaining attention for treating physical diseases in aquaculture and aquarium fish. Sturgeon is a suitable species for surgical experiments due to its industrial significance. Maintaining homeostasis is crucial during surgical procedures, and the liver plays a major role in immune regulation. High temperature is suggested to improve physiological activity and wound healing. This study investigated differences in hepatectomy sturgeons’ tolerance and histopathological responses of internal organs. Moreover, this study investigated the effects of high temperatures on wound healing and hematopoietic recovery in fish undergoing surgical procedures. The liver condition was found to play a pivotal role in the analysis, and cortisol levels were affected by anesthesia. The results showed that high temperature facilitated hematopoietic recovery and wound healing, but excessive induction of physiological activity caused damage. Managing high temperatures and liver conditions induced a remarkable improvement in wound healing. However, anesthesia itself can be a significant stressor for fish, and wound healing requires a greater amount of energy. Further research is needed to understand the stress factors caused by surgical procedures and anesthesia and to promote animal welfare in fishery products.