Salmon lice loads on Atlantic salmon smolts associated with reduces welfare and increased population mortalities

Modelling potential impacts of salmon lice Lepeophtheirus salmonis on Atlantic
salmon Salmo salar requires estimation of the levels that cause serious sub-lethal physiological impacts and direct mortality. This document analyses results from existing laboratory experiments to identify 2 thresholds; the lower threshold (T1) estimates the level at which lice loads cause systemic sub-lethal effects on smolts likely to impact performance, and the upper threshold (T2) identifies the lice load causing direct mortality.