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Diseases of Aquatic Organisms

    DAO prepress abstract   -  DOI: https://doi.org/10.3354/dao03674

    Prolonged low-salt immersion effectively controls Flavobacterium columnare infection of Murray cod Maccullochella peelii peelii

    Zhenguo Zhang, Shuang Hao, Xiaohui Bai, Hongzheng You, Yanhui Wu, ShouMing Feng, Lianying Zhang, Zhang Luo*

    *Corresponding author:

    ABSTRACT: A disease outbreak occurred in Murray cod Maccullochella peelii peelii in a recirculating aquaculture farm in Tianjin city, China, in 2019. Strain MRX-2019 was isolated and considered to be the etiological pathogen. It was identified as Flavobacterium columnare based on a 16S rDNA gene sequence analysis and physiological and biochemical tests. The effect of salinity on the growth of strain MRX-2019 was investigated in vitro. Salinity > 4‰ (i.e., 6‰) inhibited MRX-2019 growth, whereas 8 and 10‰ salinity killed it. The effect of 4‰ salinity on F. columnare was not significant (p > 0.05). When MRX-2019-infected Murray cod were treated with 4, 6, or 8‰ salinity, the mortality rate was reduced by 8.9, 67.76, or 75.56%, respectively, compared with that of the control. However, the mortality rate increased by 7.77% at 10‰ salinity. In this study, we found that maintaining the fish in freshwater with 6–8‰ salinity effectively reduced the mortality of these fish when infected with F. columnare. The findings of this study provide an environmentally friendly control strategy for columnaris disease in Murray cod.