Pukyong National University

PKNU Successfully Suppresses Parasites in Farmed Fish Using a Newly Discovered Korean Microalga

- Research Team Led by Professor Hyun-Ho Shin Confirms Inhibitory Effects Against Parasitic Ciliates in Olive Flounder

Professor Hyun-Ho Shin of the Division of Fisheries Life Sciences (Major in Aquaculture Applied Life Science) at Pukyong National University and a research team led by Professor Min-Jae Kim of the Korea Institute of Ocean Science and Technology(KIOST) School have demonstrated the potential of using marine microalgae as an environmentally friendly method for controlling scuticociliatosis, one of the most serious diseases affecting the aquaculture industry.

Through their collaborative research, the research team discovered that Fukuyoa koreensis, a benthic dinoflagellate species, can effectively inhibit the proliferation of Miamiensis avidus, a parasitic ciliate responsible for significant losses in olive flounder aquaculture farms.

Notably, Fukuyoa koreensis is a newly identified microalgal species first reported to the world from Korean coastal waters by Professor Shin’s research team. The species name “koreensis” reflects its Korean origin. The study is considered highly significant from both academic and industrial perspectives, as it demonstrates how a marine biological resource discovered in Korea can be developed into a practical disease-control technology for the aquaculture sector.

Scuticociliatosis is a disease caused by the parasitic ciliate Miamiensis avidus and is recognized as one of the most devastating diseases affecting olive flounder aquaculture, often resulting in mass mortality events. At present, fish farms primarily rely on chemical treatments and aquaculture management practices to control outbreaks, while antibiotics are sometimes used to prevent secondary bacterial infections. However, growing concerns over drug resistance and environmental residues have highlighted the need for environmentally friendly and sustainable disease-control technologies.

To address this challenge, the research team compared the antiparasitic effects of 13 microalgal species isolated from Korean coastal waters. The results showed that Fukuyoa koreensis exhibited the strongest inhibitory activity against the parasite among all species tested. Notably, the researchers found that not only the microalgal cells themselves but also the cell-free filtrate obtained from the culture medium effectively suppress parasite growth. The inhibitory effect remained significant even under diluted conditions, demonstrating the robustness of the bioactive compounds produced by the microalga. The team also evaluated the safety of the treatment using olive flounder juveniles. No obvious abnormal behavior or signs of acute toxicity were observed in the treated fish. Although increased expression of several stress-related genes was detected, the overall results indicated a high level of safety, supporting the potential application of this technology in commercial aquaculture operations.

The researchers believe that the antiparasitic activity is likely attributable to bioactive compounds or toxin-like substances secreted by Fukuyoa koreensis. Future studies will focus on identifying these active compounds and elucidating their mechanisms of action. The team also plans to advance the technology into a sustainable and environmentally friendly aquaculture solution through the development of mass-cultivation techniques and further commercialization research.

The study is particularly significant because it demonstrates that the allelopathic effects of a benthic dinoflagellate can be utilized to control parasites affecting farmed fish. By presenting a novel biological control strategy capable of reducing reliance on antibiotics and chemical treatments, the research offers a promising pathway toward the development of a more sustainable and environmentally responsible aquaculture industry.

Professor Hyun-Ho Shin stated, “This study demonstrates that a microalgal resource discovered in Korea can be utilized for the control of aquatic diseases. We expect the findings to contribute not only to the development of environmentally friendly aquaculture technologies but also to the expanded industrial utilization of marine biological resources.”

The research findings were published on June 15 in 'Aquaculture Reports', an international journal in the field of aquaculture ranked within the top 10% of journals in the JCR category, under the title “Inhibitory Effects of Cells and Culture Filtrate of the Epiphytic Dinoflagellate Fukuyoa koreensis on the Parasitic Ciliate Miamiensis avidus.” The study was supported by the “Development of Marine Biotoxin Production and Functional Utilization Technologies” program funded by the Ministry of Oceans and Fisheries.