Chalimus Stages in Salmon Lice

Two similar but independent experiments were conducted at the Sea Lice Research Centre (Experiment 1) and the Institute of Marine Research in Bergen (Experiment 2) to determine the number of chalimus stages in L. salmonis. Experiment 1 used observations of abandoned L. salmonis exuviae in incubators to identify molting events prior to the preadult 1 stage. In experiment 2 morphometrics were used to identify the number of distinct morphological groups of L. salmonis chalimus larvae and to assess molting in incubators.
In both experiments Atlantic salmon (Salmo salar) were stocked in 500L fish tanks (1x1x0.5 m) with flow-through full salinity seawater (34.5‰, 10±0.3°C). The fish were infected with L. salmonis copepodids as described by Hamre et al. [17 (link)] using 150-200 copepodids fish^-1. The lice used belong to the laboratory strains LsGulen and LsOslofjord [17 (link),18 ]. Both experiments were carried out in strict accordance with Norwegian legislation and the experiment was approved by the Norwegian Animal Research Authority (permits nr. 2010/245410 and 2009/186329).