A system dynamics approach to sea lice control in Norway

Abstract

Various methodologies have been used to model the epidemiology and economics of aquatic diseases, including input-output models, benefit-cost analysis, linear programming, compartment models based on differential equations, and spatial models. Despite the virtues of each of these models, there is a need to develop a more integrated approach to the epidemiology and economics of disease that better represents and captures existing feedback mechanisms that can influence the success of disease control interventions and their cost-effectiveness. In this paper, we motivate the use of system dynamics (SD) modeling in the context of sea lice control in Norwegian farmed salmon. Separate models of sea lice and salmon growth were designed and integrated to capture the feedbacks between them. Different simulation scenarios highlight the benefits of the approach. Model results indicated that changing the timing and type of treatment vis-à-vis current practices can markedly reduce sea lice infection pressures; such simulated practices are also more cost effective. Our approach further highlights how delays and feedbacks present in these systems influence the success of any disease control protocol, and demonstrates the utility that SD models can play in aquatic health.