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The Lice


The genera Lepeophtheirus and Caligus parasitize marine fish, in particular those species that have been recorded on farmed salmonLepeophtheirus salmonis and various Caligus species are adapted to salt water and are major ectoparasites of farmed and wild Atlantic salmon. Several antiparasitic drugs have been developed for control purposes. L. salmonis is the best understood in the areas of its biology and interactions with its salmon host.


Some evidence indicates that sea lice flourishing on salmon farms can spread to nearby wild juvenile salmon and devastate these populations. Sea lice, particularly L. salmonis and various Caligus species, including C. clemensi and C. rogercresseyi, can cause deadly infestations of both farm-grown and wild salmon. Sea lice migrate and latch onto the skin of wild salmon during free-swimming, planktonic nauplii and copepodid larval stages, which can persist for several days. Large numbers of highly populated, open-net salmon farms can create exceptionally large concentrations of sea lice. When exposed in river estuaries containing large numbers of open-net farms, mathematical models have suggested that many young wild salmon may be infected. Adult salmon may survive otherwise critical numbers of sea lice, but small, thin-skinned juvenile salmon migrating to sea are highly vulnerable.

Public Reporting

A new Order was laid in the Scottish Parliament on 21 December which supports the Scottish Government’s implementation of sea lice policy and management of sea lice on fish farms.

Its provisions introduce a step change in sea lice reporting. It requires average weekly female sea lice numbers per fish to be reported to Scottish Government one week in arrears, in place of current arrangements which require reporting only where specific levels are met or exceeded


The additional information will help the Fish Health Inspectorate to monitor and enforce policy on sea lice management. The data will be published to promote transparency.

As well as making the reporting of average sea lice numbers mandatory, the Order will require a reason for no count to be given and will refer to the penalties for not doing so.

The policy was developed through the Farmed Fish Health Working Group and a six week consultation on the new Order was held with relevant parties including the farmed fish sector, regulators, wild salmon interests, environmental interests and professional veterinarians.

If satisfactory measures cannot be demonstrated then enforcement action will be taken.

The concern here is that, as with all  salmon farming unlawful actives, no enforcement action will actually be taken. At best, there will be a friendly "off record" phone call from Fergus Ewing.

What Actually Happens

More to follow...

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