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Diseases of Aquatic Organisms

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DAO 56:105-113 (2003)  -  doi:10.3354/dao056105

Bacterial influences on Atlantic halibut Hippoglossus hippoglossus yolk sac larval survival and start feed response

David W. Verner-Jeffreys1,3, Robin J. Shields2,4, T. Harry Birkbeck1,*

1Institute of Biomedical and Life Sciences, Division of Infection and Immunity, Joseph Black Building, University of Glasgow, Glasgow Gl2 8QQ, UK
2Seafish Aquaculture, Ardtoe, Argyll PH36 4LD, UK
3Present address: CEFAS Laboratory, The Nothe, Weymouth, Dorset DT4 8UB, UK
4Present address: Aquaculture Wales, University of Wales, Swansea, Singleton Park, Swansea SA2 8PP, UK
*Corresponding author. Email:

ABSTRACT: A bacteria free halibut larval rearing system was used to test 20 bacterial isolates, from British halibut hatcheries, for their toxicity towards halibut yolk sac larvae under microbially controlled conditions. The isolates tested spanned a range of genera and species (Pseudoalteromonas, Halomonas marina, Vibrio salmonicida like, Photobacterium phosphoreum and V. splendidus species). A pathogen of turbot, Scophthalmus maximus, V. anguillarum 91079, and 2 isolates from adult halibut were also included. Isolates were inoculated, at a concentration of 5 x 102 cfu ml-1, into flasks containing 25 recently hatched axenic halibut larvae, using a minimum of 3 flasks for each treatment. Control survivals to 38 d post hatch for the 3 experiments averaged 84, 51.5 and 49%, respectively. With the exception of V. anguillarum 91079, which was highly pathogenic towards halibut yolk sac larvae, there was no statistically significant difference in survival between the controls and the different treatments. This suggests that most of the bacteria routinely isolated from halibut hatcheries are not harmful to yolk sac larvae, even though most flasks contained in excess of 5 x 106 cfu ml-1 of the inoculated organism when the experiments were terminated. Three organisms previously shown to inhibit growth of bacteria in vitro were tested for their ability to protect halibut yolk sac larvae against invasion by V. anguillarum. In 4 separate challenge experiments none of the test isolates, a Pseudoalteromonas strain and 2 Carnobacterium like organisms, showed any protective effect. To investigate how particular bacteria influence their start feed response, larvae were fed axenic and gnotobiotic Artemia colonized with a range of different Vibrio spp., and examined after 8 d. There were no statistically significant between treatment differences in the proportion of Artemia containing larvae, indicating that bacterial contamination of the live food does not appear to influence initiation of the feeding response.

KEY WORDS: Halibut larvae ·Bacteria · Probiotic · Vibrio anguillarum

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