|Microbiological aspects in marine larviculture|
Dehasque, M.; Bogaert, P.; Sorgeloos, P.; Verdonck, L.; Nelis, H. (1993). Microbiological aspects in marine larviculture, in: Seventh forum for applied biotechnology, PAND, Gent 30 September - October 1993, abstracts. pp. 59
In: (1993). Seventh forum for applied biotechnology, PAND, Gent 30 September - October 1993, abstracts. RUG: Gent. 150 pp., more
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VLIZ: Proceedings 
|Document type: Conference paper|
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- Dehasque, M., more
- Bogaert, P.
- Sorgeloos, P., more
Due to the rapid expansion of fish farming, the increasing production of larvae leads to the intensification of production techniques. More disease problems, often related to bacterial infections, occur and hygiene management becomes more important. Often the live food is suspected to be a source of bacterial contamination. In recent years much attention is given to microbiological research on bacterial aspects related with the live feed, Artemia and rotifers. A first topic covers the quantitative and qualitative study of the bacteriological environment in live food production units in different southern European hatcheries, using different production techniques. An extensive sampling campaign resulted in a collection of more than 1000 bacterial isolates of which the dominant colony types were further characterized using cellular fatty acid fingerprints. Although the microflora in the different hatcheries can be very different, more than 40% of the live food isolates belong to Vibrio spp. Live food disinfection or the development of procedures to reduce the bacterial load (esp. potential pathogenic Vibrio spp.) is important in view of hygiene management. As the live food is considered to be an important source of potential pathogenic bacteria for the predator larvae, disinfection procedures were developed which are able to reduce the bacterial load on hatched and enriched Artemia from more than 107/g to respectively less than 104/g- 105/g without any toxic effect on the Artemia. Disease treatment/prevention in young larval stages through bioencapsulation of therapeutics/Vaccines into live food is also being investigated. Via enrichment procedures therapeutics are incorporated into the live food and fed to the larvae resulting in high therapeutic tissue levels a few hours post feeding. This technique can be used for prophylactic and/or therapeutic treatment of bacterial infections in the young larval stages when oral treatment is only possible through live food. Oral treatment is preferred over bath treatment both for environmental and stress reasons. The same principle is used for vaccination of young larvae. Artemia nauplii are incubated in a vaccine suspension for a few hours and fed to the larvae. This way of oral vaccination also results in a better overall performance, in terms of growth, compared to non-vaccinated fish. Another approach for suppressing pathogenic bacterial growth is the use of probiotics. Although still in its experimental phase, preliminary results are promising. The main principle of probiotics, improvement of intestinal microbial balance and thus of its protective action can also be applied in larviculture. Screening for strains with positive and/or antagonistic effects have to result in more stable, improved rotifer cultures which in their turn will contribute to more predictable, better controllable larval rearing.