Salmon lice treatments and salmon mortality in Norwegian aquaculture: a review

Abstract

With the expansion of Atlantic salmon aquaculture, the economic and ecological impacts of salmon lice ( Lepeophtheirus salmonis ) has increased. Norway battles this problematic parasite with various control and preventative methods within farms. We analysed two national‐level databases to examine the number of operations reported each year from 2012 to 2017 and salmon mortality rates attributable to each operation type. From 2012 to 2017, 1.4 times more operations were registered, despite only limited increases in biomass produced across this period. We detected a rapid and recent paradigm shift in the industry's approach to lice control from chemotherapeutant to non‐medicinal operations. Chemotherapeutants (azamethiphos, cypermethrin, deltamethrin and hydrogen peroxide) dominated operations from 2012 to 2015 (>81%), while mechanical and thermal treatments dominated in 2016 and 2017 (>40% and >74%, respectively). Thermal operations caused greatest mortality increases (elevated mortality for 31% of treatments), followed by mechanical (25%), hydrogen peroxide (21%), and azamethiphos, cypermethrin and deltamethrin (

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