Factors influencing the long-term dynamics of larval sea lice density at east and west coast locations in Scotland

Anna J. Harte, Alan S. Bowman, Nabeil K.G. Salama, Campbell C. Pert

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Sea lice (Copepoda: Caligidae) are marine copepods that parasitize finfish, and in cases of high infestation can result in severe epithelial damage and mortality. In Scotland, two species of sea louse, Lepeophtheirus salmonis and Caligus elongatus, pose a significant economic burden to the marine Atlantic salmon aquaculture industry, as well as potentially impacting wild salmonids. The purpose of this study was to determine how the density of pelagic sea lice is affected by external variables, in order to improve our understanding of sea lice dynamics. Long-term data from two sampling sites on the east and west coast of Scotland, UK, were modelled independently in conjunction with environmental and anthropogenic variables. Statistical analysis identified that at the east coast site, the most influential factor affecting lice density was salinity. On the west coast, salinity, rainfall, and farmed salmon production year were most influential. Molecular and morphological techniques also showed that the individuals recorded on the east coast were C. elongatus, a generalist copepod parasite, whereas only the salmonid-specific L. salmonis were found on the west. These results reiterate the role of environmental factors in influencing sea lice dynamics, and that salmonids are the primary hosts of sea lice on the west coast, but there could be non-salmonid host species as well as salmonid species influencing east coast sea lice densities.
Original languageEnglish
Pages (from-to)181-192
Number of pages12
JournalDiseases of Aquatic Organisms
Issue number3
Early online date21 Mar 2017
Publication statusPublished - 2017

Bibliographical note

We thank the skipper and crew of the ‘Temora’ (Jim Brown and Paul MacDonald) as well as the willing volunteers who participate on the Stonehaven sampling rota as part of the Scottish Government project ST03p.
We also thank Eileen Bresnan for the original idea of using the samples to analyse sea lice dynamics, Zoe Allcock for advice on the statistical analysis, Jim Raffell for assistance with the Shieldaig samples, Marine Harvest for providing west coast temperature data and Catherine Collins for guidance with the molecular identification. We recognise the valuable feedback provided by the 2 anonymous reviewers.


  • sea lice
  • Scotland
  • environmental parameters
  • Caligus elongatus
  • Lepeophtheirus salmonis


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