, Volume 617, Issue 1, pp 55–63 | Cite as

Geographic and temporal genetic structure in Lepeophtheirus salmonis from four salmon farms along the northwest and west coasts of Ireland: results from a microsatellite analysis



The marine ectoparasitic copepod of salmonids, Lepeophtheirus salmonis (Krøyer), is a major pest of farmed Atlantic salmon (Salmo salar L.) causing great economic impact. The spatial scales over which L. salmonis populations in different salmon farms are typically connected, and the temporal scales over which L. salmonis from the same farm typically undergo genetic change are largely unknown. These questions were posed in a small-scale geographic study of population structure in L. salmonis from four salmon farms, along the northwest and west coasts of Ireland, using two outgroups from Norway and Canada. The temporal stability of genetic composition was also studied in samples collected quarterly during one year from one salmon farm in Ireland. Genetic composition in L. salmonis was characterised using four nuclear microsatellites. Significant but low genetic differentiation was observed between all sites (F ST = 0.08), with no evidence that differentiation was correlated with geographic distance. Temporal genetic differentiation was also evident (F ST = 0.07). An analysis of all L. salmonis samples except the ones from Norway detected two separate clusters. Each cluster contained both geographical and temporal samples. These results are consistent with a population model in which L. salmonis in salmon farms along the northwest and west coasts of Ireland are not isolated, but are potentially subject to (i) localised ecological factors at the particular farm sites or (ii) selection post-settlement or a combination thereof.


L. salmonis Microsatellites Population studies Ireland 



This research was supported by the E.U. supported Operational Programme for Fisheries (Contract 97.IR.MR.011) coordinated by the Marine Institute, Ireland. The gifts of sea lice from Alan Walker and Christopher Todd (Scotland), Per Gunnar Kvenseth and Anne-Mette Kvenseth (Norway), John F. Burka of the Department of Anatomy and Physiology, Atlantic Veterinary College, University of Prince Edward Island (Canada), and David Jackson and Dan Hassett of the Marine Institute (Ireland) are gratefully acknowledged. D. V. Nolan was supported by an N.U.I., Galway postgraduate fellowship. The preparation of this paper was delayed by the untimely death of Dr. Richard Powell and is hereby dedicated to his memory.


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Copyright information

© Springer Science+Business Media B.V. 2008

Authors and Affiliations

  1. 1.Department of MicrobiologyNational University of IrelandGalwayIreland
  2. 2.School of Biological SciencesUniversity of AberdeenAberdeenScotland, UK

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