Practices to obtain lice counts at Norwegian salmon farms: status and possible implications for representativity

The Norwegian aquaculture industry faces several challenges. One such challenge is the prevalence of salmon lice, which adversely affect both wild and farmed salmon. At the core of the current regulatory regime are mandatory lice counts that are manually obtained from fish farms. Thus, the objective of this article was to present knowledge regarding counting practices, fish farm employees' perceptions of the strengths and weaknesses of these practices, and possible implications for representativity. Interviews comprised the main method of data collection for this research. The results addressed 3 phases of the lice-counting process: sampling, sedation, and counting. The organizational factors that may influence counting, such as training, time, and manning, are also described. Our results show variations in the choice of equipment used for different stages of the lice-counting process, including sampling and crowding time. In the interviews, employees discussed the challenges inherent in identifying different lice species and the associated developmental stages of the lice. The findings presented in this paper demonstrate the importance of documenting actual practices at the fish farms in order to optimize lice counts and should be considered by the aquaculture industry, technology developers, and industry regulators in the future.