Influence of fresh water bathing on stress response of yellowtail <I>Seriola quinqueradiata</I>

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  • ブリのストレス応答に及ぼす淡水浴の影響
  • ブリ ノ ストレス オウトウ ニ オヨボス タンスイヨク ノ エイキョウ

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Abstract

Bathing in fresh water is performed at aquaculture sites to exterminate parasites of yellowtail. However, fresh water bathing is likely to be associated with stress in fish due to the change in osmotic pressure. Here, the stress reaction after fresh water bathing was examined in yellowtail Seriola quinqueradiata followed by examination of the changes in sensitivity to infection using experimental infection. The blood cortisol concentration, which is used as a stress indicator, tended to increase at 0.5 and 1 h and then again 24h after fresh water bathing. In addition, an impact on host defense, such as reduction in phagocytic activity of leukocytes of the head kidney, was observed in five fish after 1 and 6h. When experimental infection using a nodular disease-causing bacterium, Photobacterium damselae subsp. piscicida, was carried out 1 h after fresh water bathing, the cumulative mortality rate was 90%, which was significantly higher than that in the control group. The viable bacteria count adhering to the gills was examined during the experimental infection, and adherence in the fresh water bathing group was significantly higher than that in the control group. In conclusion, fresh water bathing increases susceptibility of yellowtail to infection in addition to causing stress.

Journal

  • Aquaculture Science

    Aquaculture Science 63 (1), 79-87, 2015

    Japanese Society for Aquaculture Science

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