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Determination of the effects of increasing sea lice infestation on key osmoregulatory and stress parameters for Atlantic salmon smolts

Similarly to previous studies in result 11 with wild seatrout smolts, we conducted a further series of laboratory experiments infesting farmed Atlantic salmon with varying intensities of L. salmonis. This allowed us to determine, for the first time, a threshold level of sea lice infestation which induces physiological stress for farmed Atlantic salmon. Results from the high infestation group(25 indicated significant decreases in haematocrit and increases in plasma concentrations of chloride, glucose lactate and cortisol and plasma osmolarity, once sea lice had reached the mobile stages. Piecewise linear statistical modelling again allowed the objective determination of abrupt changes in these physiological markers, attributable to the intensity of L. salmonis infestation on individual fish.20 L. was a consistent breakpoint across several physiological markers indicating the onset of physiological stress above this lice intensity. This allowed identification of 20 as an overall threshold lice burden. This important information will be made available to the aquaculture industry and contribute to management and policy development.

Reported by

University of St Andrews, Gatty Marine Laboratory
East Sands
KY16 8HL St Andrews, Fife
United Kingdom
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