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Biol Lett. Aug 23, 2010; 6(4): 548–551.
Published online Feb 17, 2010. doi:  10.1098/rsbl.2009.0872
PMCID: PMC2936189
Temporal and spatial patterns of sea lice levels on sea trout in western Scotland in relation to fish farm production cycles
S. J. Middlemas,1* J. A. Raffell,2 D. W. Hay,1 M. Hatton-Ellis,2 and J. D. Armstrong1
1Marine Scotland Science, Freshwater Laboratory, Faskally, Pitlochry PH16 5LB, UK
2Marine Scotland Science, Shieldaig Field Station, Shieldaig, Strathcarron IV54 8XJ, UK
*Author for correspondence (s.middlemas/at/
Received October 22, 2009; Accepted January 22, 2010.
The relationship between aquaculture and infestations of sea lice on wild sea trout (Salmo trutta) populations is controversial. Although some authors have concluded that there is a link between aquaculture and lice burdens on wild fish, others have questioned this interpretation. Lice levels have been shown to be generally higher on Atlantic salmon farms during the second years of two-year production cycles. Here we investigate whether this pattern relates to lice burdens on wild fish across broad temporal and spatial axes. Within Loch Shieldaig across five successive farm cycles from 2000 to 2009, the percentage of sea trout with lice, and those above a critical level, were significantly higher in the second year of a two-year production cycle. These patterns were mirrored in 2002–2003 across the Scottish west coast. The results suggest a link between Atlantic salmon farms and sea lice burdens on sea trout in the west of Scotland.
Keywords: Lepeophtheirus, Salmo trutta, aquaculture
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