Comparative analysis on the productivity, water quality, and gut microbiome of Silurus asotus and Anguilla japonica in a biofloc system

Authors

1 Department of Animal Science and Technology, Konkuk University, Seoul 05029, Republic of Korea

2 Advanced Aquaculture Research Center, National Institute of Fisheries Science, Changwon 51688, Republic of Korea

3 Institute of Biological Resources, Jiangxi Academy of Sciences, Nanchang 330029, China

4 Animal Resources Research Center, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029, Republic of Korea

10.22092/ijfs.2025.134242

Abstract

This study investigated the effects of biofloc technology (BFT) on water quality, productivity, and intestinal microbial diversity in Far Eastern catfish and Japanese eel. A total of 450 Far Eastern catfish or 50 Japanese eels were housed in separate tanks during a 4-week experiment that compared BFT and the control group. The ammonia nitrogen (NH₄⁺-N), nitrite nitrogen (NO₂⁻-N), and nitrate nitrogen (NO₃⁻-N), along with the growth performance and the gut microbial diversity indices were evaluated. Post-breeding, NH₄⁺-N and NO₂⁻-N levels were consistently maintained below 1 mg/L in BFT tanks, while NO₃⁻-N levels exhibited continuous increases. Compared to the control group, BFT tanks showed superior growth metrics for both species, particularly Far Eastern catfish, which displayed significantly higher values for body length, body weight, and stocking density (p<0.05). Principal coordinates analysis revealed notable similarities in microbial communities across treatments. The Firmicutes phylum was predominant in the gut microflora of both fish, while Proteobacteria, Bacteroidetes, and Fusobacteria predominated in the breeding water. The Firmicutes/Bacteroidetes ratio increased in BFT group, suggesting a positive impact on growth. Operational taxonomic units ranged from 94 to 293 for Japanese eels and 234 to 353 for Far Eastern catfish. Based on Venn diagram analysis, 36 to 75 unique species were identified in Japanese eel gut samples, while Far Eastern catfish gut samples contained 72 to 145 unique species. In conclusion, BFT positively impacts water quality, fish growth, and beneficial intestinal microbes.

Keywords

Iranian Journal of Fisheries Sciences
Volume 24, Issue 5
September 2025
Pages 1063-1079

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