Estimation of external infection pressure and salmon-louse population growth rate in Faroese salmon farms

Managing salmon louse Lepeophtheirus salmonis outbreaks is a crucial part of salmon aquaculture in sea cages. Treatment management strategies can be optimized with the aid of salmon-louse population dynamic models. These models, however, need to be calibrated and validated with biologically meaningful parameters. Here, based on a time-series of lice data, we estimated 2 essential model parameters: the external infection pressure and the salmon-louse population growth rate for each active salmon farm site in the period 2011 to 2018 in the Faroe Islands. External infection pressure was found to vary between farm sites and ranged on average from 0.002 to 0.1 lice salmon-1 d-1. Further, external infection was significantly correlated with the total number of gravid lice in the Faroese farm network. Salmon-louse population growth rates were found to vary between farm sites and ranged on average from 1.7 to 5.4% d-1. These model parameter estimates are crucial in developing a salmon-louse population dynamic model for the Faroe Islands, and the method to estimate these parameters may be applicable in other aquaculture regions