Published 2006

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Publication details

Journal : Canadian Journal of Fisheries and Aquatic Sciences , vol. 63 , p. 2809–2821 , 2006

Publisher : NRC Research Press

International Standard Numbers :
Printed : 0706-652X
Electronic : 1205-7533

Publication type : Academic article

Contributors : Wells, A; Grierson, CE; Reinardy, H; Middlemiss, C.; Todd, CD; Hazon, N; MacKenzie, M; Russon, IJ; Bonga, Sjoerd E. Wendelaar; Bjørn, Pål Arne; Finstad, Bengt

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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 (Kroyer, 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 center dot 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.