Zebrafish Health, Environmental, and Water Quality Monitoring in Research Facilities: Longitudinal Trends of South Korea from 2018 to 2024
Regular monitoring of laboratory zebrafish health status is crucial for ensuring both animal welfare and scientific validity in aquatic research. While zebrafish usage in research has increased substantially due to their biological advantages and experimental benefits, including high fecundity and vertebrate similarity, systematic health monitoring remains uncommon in South Korean facilities. This study presents a comprehensive assessment of zebrafish colony health monitoring practices in South Korea, combining comparative survey data from 2018 and 2024 with microbiologic and environmental analyses of 11 facilities. Our survey revealed a trend: despite facility scale expansion (proportion of the large-scale facilities with >200 tanks increasing from 41.7% to 54.5%) and universal adoption of recirculation systems, monitoring efforts have declined. The percentage of facilities without active monitoring increased from 50.0% in 2018% to 81.8% in 2024, while awareness of monitoring necessity decreased from 91.7% to 72.7%. To investigate these issues, we conducted analyses across 11 facilities (6 research institutes and 5 local suppliers). The analysis encompassed multiple parameters: 1) detection of key infectious agents (Mycobacterium spp., Aeromonas hydrophila, Flavobacterium columnare, Pseudocapillaria tomentosa, Pseudoloma neurophilia, Pseudomonas aeruginosa) in sump tank biofilm, zebrafish specimens, and feed samples; and 2) evaluation of water chemistry parameters (pH, nitrate concentration, conductivity) in tank water. Our findings revealed that Mycobacterium spp. were present in biofilm samples from all facilities and in >80% of fish samples from research facilities. Aeromonas hydrophila was detected across all sample types. Both Mycobacterium spp. and A. hydrophila are opportunistic pathogens that necessitate careful consideration in long-term zebrafish experiments. Furthermore, evaluation of water quality analyses indicated widespread deviations from acceptable parameters, particularly in nitrate levels and pH values. Our results underscore the need for implementing standardized monitoring protocols and enhanced water system management to safeguard research integrity, animal health, and occupational safety in zebrafish facilities.
Publication trends of zebrafish studies from PubMed (1980 to 2023). (A) The numbers of search results using keywords ‘zebrafish’ and ‘zebrafish’ AND ‘Korea’ are shown. Both global and Korean publication trends have steadily increased since 1980. (B) The proportions of the search results of ‘zebrafish’ AND ‘Korea’ to ‘zebrafish’ are shown. The proportion of the Korean to global publications is increasing.
Survey results of zebrafish facilities regarding zebrafish health monitoring and environmental monitoring in the Republic of Korea in 2018 and 2024. (A–G) Survey results of 12 zebrafish facilities in 2018 are summarized. (H–N) Survey results of 11 zebrafish facilities in 2024 are summarized.
Sample preparation for heath/environmental surveillance in zebrafish facilities. All samples were kept at 4 °C until analysis. (A) Circulating water was sampled using a culture dish and disposable pipette for chemistry analysis. (B) Biofilm on the sump tank was swab-sampled and kept in the transport medium tube for further transportation. (C) Zebrafish were euthanized by hypothermia and sampled in a conical tube for health surveillance. (D) Feed (brine shrimp and/or commercial feed) was sampled in a conical tube. (E) Biofilm and water sampling locations of the zebrafish husbandry system are indicated with a red-dotted circle.
Detection prevalence of representative zebrafish infectious agent detection throughout the South Korean zebrafish facilities by PCR.
Water chemistry analysis of samples from research facilities and local zebrafish suppliers in South Korea. Acceptable ranges of each criterion are highlighted with green-colored boxes, and upper and lower limits are marked with blue dotted lines. (A) Conductivity of the environmental water (acceptable range, 550 to 650 µS/cm). (B) Nitrate concentration of the environmental water (acceptable range, <50 ppm). (C) pH of the environmental water (acceptable range, pH 6.7 to 7.3).
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