New Thresholds for Sealice Chemicals

The Fish Site
by The Fish Site
2 November 2006, at 12:00am

UK - New thresholds for medicines used to treat sea lice infestations in marine fish farms are to be introduced by the Scottish Environment Protection Agency (SEPA).

It follows the publication in 2005 of a five year study monitoring and measuring the potential environmental impacts of using sea lice medicines. The independent PAMP* report confirmed there was no evidence of any impact from these substances on the environment which could be separated from the natural variation found in marine ecosystems.

As a result, the modelling approach which is currently used to determine the license limits for sea lice bath treatments will be changed, extending the time period over which the dispersal of the medicine is modelled from three to six hours.

The use of the revised modelling approach removes some of the precaution in the way that the sea lice treatment Excis is licensed, allowing fish farmers to more effectively treat sea lice infestations at marine cage fish farms. More effective treatment of such infestations may lead to benefits for wild salmon populations as there are anecdotal links between declines in salmon populations and the occurrence of sea lice on wild salmon.

Douglas Sinclair of SEPA said: “We strive to use the best available science to continually improve the way we regulate the fish farming industry and the means by which environmental protection is ensured. The conclusion of the PAMP study has enabled us to review some of the precaution which was implicit in the modeling approach used to derive limits for the use of sea lice chemicals. The change should allow fish farmers to more effectively deal with sea lice infestations while still ensuring environmental protection.”

Full details of the PAMP report are available at and the revised modeling documentation can be found at

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