Physiological effects of simultaneous, abrupt seawater entry and sea lice ( Lepeophtheirus salmonis ) infestation of wild, sea-run brown trout ( Salmo trutta ) smolts

Alan Wells, Christal E Grierson, Monique MacKenzie, Iain J Russon, Helena Reinardy, Claire Middlemiss, Pål A Bjørn, Bengt Finstad, Sjoerd E. Wendelaar Bonga, Christopher D Todd, Neil Hazon

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55 Citations (Scopus)


For wild, sea-run brown trout (Salmo trutta) smolts, the physiological consequences of abrupt transfer to seawater and simultaneous challenge with copepodid larvae of the sea louse, Lepeophtheirus salmonis (Krøyer, 1837), were investigated in the laboratory. Analysis of osmoregulatory, metabolic, and stress markers allowed the derivation of a sublethal threshold burden of L. salmonis, above which the host suffers major physiological stress. Noticeable lice effects, consistent across all measured markers, were not observed until L. salmonis developed to the mobile preadult and adult stages. Preadult L. salmonis caused significant increases in plasma chloride, osmolality, glucose, lactate, and cortisol and a significant reduction in haematocrit. Piecewise linear statistical approaches allowed the determination of abrupt changes in these physiological markers, attributable to the intensity of L. salmonis infestation on individual fish, and identification of overall threshold lice burdens. Thirteen mobile lice·fish–1 (weight range 19–70 g) was a consistent breakpoint across several physiological measures. This information will provide a valuable, objectively derived tool to aid in the formulation of effective wild fisheries management policy concerning S. trutta conservation. Résumé
Original languageEnglish
Pages (from-to)2809-2821
Number of pages13
JournalCanadian Journal of Fisheries and Aquatic Sciences
Issue number12
Publication statusPublished - Dec 2006


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