FacultyCenter of Education and Research for Hope-Emergence, and Shunichiro Oshima, Faculty Kuroshio Zone Integrated Faculty of the School of Integrated Sciences, have been published in the journal *Aquacultural Engineering*.
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Preventing Fish Diseases with UV-C LEDs as a Replacement for Mercury Lamps
—A Study on New Sterilization Technologies for Land-Based Aquaculture Systems—
Research findings FacultyCenter of Education and Research for Hope-Emergence, and Faculty Shunichiro Oshima of the Kuroshio Region Faculty Science Faculty in the School of Integrated Sciences have been published online in the journal *Aquacultural Engineering*.
Deep ultraviolet light-emitting diodes (UV-C LEDs) are attracting attention as next-generation sterilization devices to replace conventional ultraviolet sterilizers using mercury lamps, due to their characteristics such as long lifespan, mercury-free operation, and no need for warm-up.In recirculating aquaculture systems (RAS), mercury lamp sterilizers are used to prevent fish diseases; however, they face challenges such as high power consumption and high operating costs. Therefore, this study investigated the sterilization effects of UV-C LED irradiation on various fish disease-causing bacteria, as well as the effectiveness of UV irradiation in suppressing the spread of bacterial infections toward the practical application of deep ultraviolet light-emitting diodes in RAS.
The test organisms included Edwardsiella tarda, the causative agent of edwardsiellosis, Vibrio rotiferianus (the causative agent of vibriosis), Tenacibaculum maritimum (the causative agent of gliding bacteriosis ), Lactococcus garvieae (the causative agent of alpha-hemolytic streptococcosis), Streptococcusiniae (the causative agent of beta-hemolytic streptococcosis), and Nocardia seriolae (the causative agent of nocardiosis).First, we investigated the bactericidal effect of UV-C LED irradiation on these test bacterial suspensions. Next, after evenly mixing the E. tarda suspension within the RAS, we irradiated it with UV light and measured the viable bacterial count in the seawater over time. Furthermore, in addition to the bactericidal effect of UV-C LED irradiation, we estimated the sterilization rate within the tank using simulation based on the water volume and circulation flow rate in the RAS.The results showed that UV-C LED irradiation was effective against all test bacteria, and the number of viable E. tarda bacteria in the RAS decreased over time following UV irradiation. Furthermore, the simulation results indicated that it is possible to predict the sterilization rate based on water volume and circulation flow rate under UV-C LED irradiation, confirming the effectiveness of this method in suppressing bacterial infections transmitted through aquaculture water, including E. tarda.
These research findings demonstrate the potential for a new disinfection method using UV-C LEDs to serve as a reliable technology for use in fish farming operations. It is expected to contribute to the realization of sustainable aquaculture systems that prevent fish diseases while minimizing environmental impact.
[Paper Information]
Paper Title: Infection control of fish pathogenic bacteria using deep ultraviolet irradiation in recirculating aquaculture systems
Authors: Mao Hokin, Natsumi Nagahiro, Hiroaki Enomoto, Naoto Yabuki, Syun-ichirou Oshima
Journal Name: Aquacultural Engineering
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