Suspicious patterns in self-reported sea lice data may be explained by population dynamics

Abstract

A recent study by Jeong et al. (2023) demonstrates a puzzling disparity in self-reported sea lice data between Norwegian and Canadian fish farmers. The authors investigate the ratio of reported adult female lice to total mobile lice abundance and find a striking “cliff effect” in the Norwegian data around the maximum permissible sea lice threshold. It is suggested that intentional or unintentional under-reporting is a major reason for the observed effect. In this correspondence, we argue that the observed effect actually reflects an inherent population dynamic characteristic, arising from the frequency of delousing operations in Norwegian farms.