New biocides used against sea lice compared to organo-phosphorous compounds
Boxaspen, K.; Holm, J.C. (1992). New biocides used against sea lice compared to organo-phosphorous compounds, in: De Pauw, N. et al. (Ed.) Aquaculture and the Environment: reviews of the International Conference Aquaculture Europe '91, Dublin, Ireland, June 10-12, 1991. EAS Special Publication, 16: pp. 393-402
In: De Pauw, N.; Joyce, J. (Ed.) (1992). Aquaculture and the Environment: Reviews of the International Conference Aquaculture Europe '91, Dublin, Ireland, June 10-12, 1991. Special Publication European Aquaculture Society, 16. European Aquaculture Society: Gent. ISBN 90-71625-10-9. 536 pp., more
In: Special Publication European Aquaculture Society. European Aquaculture Society: Bredene. ISSN 0774-0689, more
|
| Available in | Authors |
|
Document type: Conference paper
|
| Abstract |
Experiments with pyrethrum, a flower extract normally used as an insecticide, have been carried out at Austevoll since 1989. Different types of administration medtods have been tested and a practical, large-scale method to reduce salmon lice infestation is developed. A large-scale experiment (3 000 salmon, 700g) caried out in February 1991 resulted in a delousing effect of 96%. In the system used it is easy to recollect the pyrethrum treatment solution. If some of the treatment solution should escape it is readily broken down by sunlight in short time. Pyrethrum has a long history of use as an insecticide and the effects on warm-blooded animals (including man) are well documented. No negative effects have been documented on humans. On the contrary , doses of up to 20g have been taken every day as an inhibitor against internal parasites. The effect on fish are not fully documented in the way described here but so far we have had no loss of fish contributed to the use of pyrethrum. Organo-phosphorous compounds as trichlorfon and dichlorvos have been used so far in the combat of the lice problem. Consumers as well as fish farmers are however getting aware of the potential ill effects of these compounds. Dichlorvos acts as a nerve poison and protection of skin, eyes, and mouth is highly recommended and necessary when handling the compounds. Fish have to be retained from the market at least 14 days after treatment (Norway) and in this time new build-up of lice often occur. The alternatives listed above, will probably not need such rigid marketing restrictions. At the end of 1990 farmers claimed that they had started to use sliced onions (Allium cepa), to combat sea lice and that it worked. In early 1991 this statement was modified somewhat to comply only for the younger stages of the lice. Tests at our Institute with onion extract show no acute lethal effects on adult and preadult stages of the lice. However, it is not unlikely that onion compounds in seawater will be able to repel the free swimming stages of the lice since such effects are well known to insects. Garlic (Allium sativum) is also being introduced, One of Norway's largest producers of fish feed have recently made up 50 tonnes moist pellet containing garlic to test if this will have any effect on the lice population. Garlic in some form have been tried before but no significant results have been reported. The fish fillet did however get a detectable taste of garlic. Compared to the positive effect of chemicals like Ivermectin administered orally it is not unlikely that a feed compound can affect the lice in some way. Both onion and garlic have been further tested during 1991 at Austevoll Aquaculture Research Station. Both have been mixed in moist pellet at a 10% level (wet weight basis ). The salmon fed onions showed at no time lower concentrations of lice but the salmon fed garlic had a significantly lower level of lice compared to the control after 14 days. |
|
