Search Results (4)

Sebastes thompsoni is a cold-water rockfish of commercial and ecological value off the coast of Korea, requiring conservation management. We analyzed seven microsatellite loci to assess genetic diversity, population structure, and historical effective population size (N_e) of five populations obtained from the South and East Seas of Korea in 2018. The observed heterozygosity (H_O = 0.759–0.816) was higher than previously reported, and none of the STRUCTURE, DAPC, or AMOVA analyses detected geographic differentiation among samples from the South and East coasts of Korea, indicating a single population within these coasts. There was genetic flow between the five groups, with migration rates ranging from 4.1 to 19.11. However, the current N_e of all populations is estimated to be <1000, and VarEff-based reconstructions indicate a recent, severe bottleneck following an expansion approximately 600–1200 years ago (100–200 generations ago). This suggests that genetic diversity loss may persist in the future due to long-term habitat loss, fishing pressure, and ocean current fluctuations. Therefore, S. thompsoni should be established as a single management unit covering the Korean Peninsula coast, and habitat protection, overfishing control, genetic management type resource release using various mother and broodstock, and periodic genetic monitoring should be promoted. This study provides evidence to guide efforts to secure long-term genetic resilience and sustainable management of S. thompsoni in Korean coastal waters. Full article

Korean rockfish, Sebastes schlegeli, a coastal species, is vulnerable to pollutants such as microplastics and bacteria. While interactions between microplastics and other pollutants have been studied, little is known about microplastic and bacteria interactions. This study examined the effects of combined exposure to polystyrene microplastics in the form of microbeads (MB; 0.2 µm, 5 and 50 beads/L) and Streptococcus iniae (1 × 10⁵ and 1 × 10⁷ CFU/mL) for five days on oxidative stress and apoptosis in Korean rockfish. We assessed the mRNA expression and activity of oxidative stress markers (SOD, CAT, H₂O₂, NO, CYP1A1, GST), plasma LPO levels, and caspase-3 expression in liver tissue. Co-exposure to high MB and S. iniae concentrations significantly elevated oxidative stress and apoptosis markers, suggesting enhanced toxicity. This may result from MB facilitating pathogen transport into the fish, indicating microplastics can act as vectors for bacterial infection in aquatic environments. Full article

Aquaculture, a crucial sector of the global food industry, faces a myriad of issues due to parasitic invasions. One such parasite, Microcotyle sebastis, which afflicts Korean rockfish in South Korea, has a significant economic impact. The impending danger of resistance to traditional anthelmintics necessitates the exploration of new antiparasitic candidates. Although the efficacy of salinomycin against aquatic parasites such as ciliates and sporozoans is known, its influence on monogeneans has yet to be studied. Therefore, this study investigated the efficacy and safety of salinomycin for the treatment of M. sebastis infections, presenting the first exploration of salinomycin’s therapeutic potential against monogeneans. In vitro examinations revealed a minimum effective concentration of salinomycin of 5 mg/kg, which led to necrosis of the haptor upon dislodging from the gill filaments. The one-time oral administration of the drug at concentrations of 5 mg/kg and 10 mg/kg showed a significant dose-dependent reduction in parasite counts, with no apparent behavioral side effects in Korean rockfish. Biochemical analyses monitored the liver, heart, and kidney enzymes, specifically aspartate transaminase (AST), alanine transaminase (ALT), blood urea nitrogen (BUN), and creatine kinase–myocardial band (CK-MB). At both 20 °C and 13 °C, no significant differences were observed in the levels of AST and ALT. However, at 20 °C, alterations in BUN levels were evident on Day 14, a deviation not observed at 13 °C. The CK-MB analysis revealed elevated enzyme levels at both temperatures when compared to the control group, reflecting the similar changes observed in terrestrial animals administered salinomycin. The biochemical data suggest that the oral administration of salinomycin is potentially more favorable at 13 °C than at 20 °C. Although our findings warrant further comprehensive studies, including on the long-term and potential effects on nontarget species and water quality, they also suggest that salinomycin could be considered as an alternative or adjunctive treatment if resistance to the currently used praziquantel against M. sebastis is confirmed. Full article

Parasitic infections pose significant challenges in aquaculture, and the increasing resistance to conventional anthelmintics necessitates the exploration of alternative treatments. Levamisole hydrochloride (HCl) has demonstrated efficacy against monogenean infections in various fish species; however, research focused on Microcotyle sebastis infections in Korean rockfish (Sebastes schlegelii) remains limited. Therefore, this study aimed to evaluate the efficacy of levamisole HCl against M. sebastis infections in Korean rockfish with the goal of optimizing anthelmintic usage in aquaculture. In this study, we first assessed the susceptibility of M. sebastis to levamisole HCl in vitro. Subsequently, in vivo evaluations were conducted to assess the drug’s efficacy, safety, and to identify optimal administration methods. In vitro experiments revealed concentration-dependent sensitivity of M. sebastis to levamisole HCl, with a minimum effective concentration (MEC) of 100 mg/L. In vivo experiments employed oral administration, intraperitoneal injection, and immersion treatments based on the MEC. Oral administration proved to be a safe method, yielding efficacy rates of 27.3% and 41.6% for 100 mg/kg and 200 mg/kg doses, respectively, in contrast to the immersion and injection methods, which induced symptoms of abnormal swimming, vomiting, and death. Biochemical analyses conducted to assess the safety of levamisole HCl revealed a transient, statistically significant elevation in the levels of glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT) on day three post-administration at 20 °C. Following this, no substantial differences were observed. However, at 13 °C, the enzyme levels remained relatively consistent, emphasizing the role of water temperature conditions in influencing the action of levamisole HCl. Our research findings substantiate the efficacy of levamisole HCl against M. sebastis in Korean rockfish, underscoring its potential for safe oral administration. These results provide valuable insights for developing parasite control strategies involving levamisole HCl in Korean rockfish populations while minimizing adverse impacts on fish health and the environment. However, this study bears limitations due to its controlled setting and narrow focus. Future research should expand on these findings by testing levamisole HCl in diverse environments, exploring different administration protocols, and examining wider temperature ranges. Full article