Modelled distribution of salmon lice in a Norwegian fjord

Abstract

Salmon lice is a huge problem for both wild and farmed salmonid fish in fjords. An assessment of salmon lice in a fjord system will bring forward the knowledge of wild salmonid fish stocks and help manage salmonid fish farming. Numerical models have been used to produce time series of salmon lice distribution in the Norwegian fjord Sognefjorden. Currents and hydrography were calculated from a high resolution, three-dimensional ocean model. Inside the fjords, detailed wind forcing was necessary, and these winds were produced by a meso-scale atmospheric model. The distribution of salmon lice was calculated by a three-dimensional particle advection model including temperature dependent growth. The model results show that the variability in salmon lice distribution is huge for the Norwegian fjord areas, with spreading of lice with the currents ranging from 0 to 100 km within only a few days. We will show the simulated encounter rate of salmon smolt on its way to the ocean and salmon lice, and show how different locations of fish farms affect this.