monitoring sea lice burdens

Interactions with Aquaculture Project

seine netting post smolts at Camas na Gaul

seine netting post smolts at Camas na Gaul

Imagesea lice on sea trout

sea lice on sea trout

Image

Since Scotland’s first fish farm started operating in Loch Ailort in 1967 there has been conflict between wild fish and aquaculture interests.  In 1999 a group was set up to bring together representatives from Scottish Government, aquaculture and wild fish interests to address this conflict.  Since then Area Management Agreements (AMAs) have been signed throughout the west coast of Scotland with the emphasis on finding local solutions to the problem.  These commit fish farms within a given area to a range of objectives including strategic lice treatments and synchronised production cycles.  The free flow of information between signatories of an AMA is also a central tenet of the process.

Lochaber Fisheries Trust is a signatory to three AMAs – Linnhe/Lorne/Etive/Sound of Mull/Sunart, Loch Ailort and Loch Nevis – and all marine farm sites in Lochaber are covered by AMAs.  We attend regular meetings to discuss progress on lice control, escape prevention and the health of wild fish stocks with representatives from local farm companies.  For many years government has provided funding for the Trust to monitor lice levels on wild sea trout post smolts by seine netting in sea lochs.  We have collected a dataset that clearly demonstrates a biennial cycle in lice levels in Upper Loch Linnhe linked to the local fish farm production cycles.  Netting in other areas has been more problematic but we recently found a site at Loch nam Uamh near Arisaig.  There is a pressing need to improve our knowledge of sea lice distribution and dispersal patterns from farms.

There have been clear improvements in farm lice levels and escapes since 1999.  It is impossible to quantify how much of this is due to conversations between wild fish and farms, and how much is because of the availability of improved lice treatments, cage technology and the development of better farm practices.  However, salmon and particularly sea trout numbers on the west coast are still at worryingly low levels and high lice levels and farm escapes continue to occur.  The Trust is continuing to engage with its AMG partners, but it is becoming increasingly clear that the local influence of AMAs is limited and national action will be required to solve these problems.

The percentage of sea trout post smolts infected with lice (prevalence) and the average number of lice per fish (abundance) in seine netting samples from Camas na Gaul.

The percentage of sea trout post smolts infected with lice (prevalence) and the average number of lice per fish (abundance) in seine netting samples from Camas na Gaul.

Lochaber Fisheries Trust