Introduction
Parasitic salmon lice (Lepeophtheirus salmonis) remain a significant economic and welfare challenge faced by the salmon farming industry. Studies show that salmon lice account for a significant proportion of biological losses and the consequent loss of revenue to the industry (e.g. Walde et al. 2023). While reactive treatments can mitigate these losses (Mustafa 2001) the most common types of treatments used today have been linked to an increased prevalence of injuries and wounds, reduced growth, and increased mortality rates (Overton et al. 2001). In response to this welfare paradox, several innovative technologies for the prevention or control of salmon lice infestations are increasingly utilized. While some of these have been shown to successfully reduce the infestation burden or need for reactive treatments (e.g., Cerbule & Godfroid 2020; Gr��ntvedt et al., 2018; Stien et al., 2016; Worm et al., 2026), studies investigating the economic impact of such strategies are still scarce. Yet, this knowledge can unlock the potential for production optimization, providing an invaluable contribution to the future of salmon farming. We therefore provide an economic analysis of one of these innovative technologies: optical delousing. Optical delousing is a non-handling, in-pen, control strategy in which laser pulses are used to remove lice from salmon and has previously been shown to decrease by half the number of reactive treatments (Worm et al. 2026).
Methods
We used a bioeconometric model incorporating baseline mortality and temperature-dependent growth for the grow-out phase, with temperature predictions for each of the 13 production areas (PAs) defined by the Norwegian Traffic Light System. We parametrized the model with empirical data from the literature and from reports submitted by farmers to the Norwegian government, and calculated production cost, revenue and net profitability for the production cycles obtained. To contrast the cost of salmon lice under scenarios in which production cycles utilize or not optical delousing as control strategy, we simulated 2000 reactive treatment schedules per scenario. We used temperature-dependent weekly probabilities of treatment obtained from Worm et al. (2026), where treatment probability depends on the use of the control strategy. Based on the literature, we assumed treatments incurred lost feeding days (i.e., lost growth), excess mortality, and decreased product quality at harvest. Frequencies for different treatment types were calculated from official reports (BarentsWatch, n.d.), and excess mortality rates per treatment type were obtained from Walde et al. (2021).
Results
Our simulations recovered the expected effect of the control strategy on reducing the number of treatments across all 13 production areas analysed. This reduction in treatments due to the use of the control strategy led to a ca. 45% average (across the 2000 simulated treatment schedules for each of the 13 PAs) mitigation in the excess mortality resulting from treatments observed in scenarios when no control strategy was deployed. This resulted in a mean increase in live biomass at the time of harvest of over 400 tones, and a mean increase in profit of 3.79 (NOK kg gutted-1). This increase in profit was despite the increase in total costs resulting from the added cost for the control strategy, as well as the increase in cost for feed, due to the reduction in lost feeding days.
Conclusions
Our results demonstrate that optical delousing is an economically viable control strategy. The economic benefit of control incorporates increased growth by avoiding lost feeding days, reduction of handling-related mortality, and better product quality at harvest. Even more, our results reinforce the idea that investing in welfare of farmed fish can provide good economic returns to the industry.
References
BarentsWatch. (n.d.). Data. https://www.barentswatch.no/data
Cerbule, K., & Godfroid, J. (2020). Salmon Louse (Lepeophtheirus salmonis (Kr��yer)) Control Methods and Efficacy in Atlantic Salmon (Salmo salar (Linnaeus)) Aquaculture: A Literature Review. Fishes, 5(2). https://doi.org/10.3390/fishes5020011
Gr��ntvedt, R. N., Kristoffersen, A. B., & Jansen, P. A. (2018). Reduced exposure of farmed salmon to salmon louse (Lepeophtheirus salmonis L.) infestation by use of plankton nets: Estimating the shielding effect. Aquaculture, 495, 865-872. https://doi.org/10.1016/j.aquaculture.2018.06.069
Mustafa, A., Rankaduwa, W., & Campbell, P. (2001). Estimating the cost of sea lice to salmon aquaculture in eastern Canada. Can Vet J, 42(1), 54-56.
Overton, K., Dempster, T., Oppedal, F., Kristiansen, T. S., Gismervik, K., & Stien, L. H. (2019). Salmon lice treatments and salmon mortality in Norwegian aquaculture: a review. Reviews in Aquaculture, 11(4), 1398-1417. https://doi.org/10.1111/raq.12299
Stien, L. H., Dempster, T., Bui, S., Glaropoulos, A., Fosseidengen, J. E., Wright, D. W., & Oppedal, F. (2016). 'Snorkel' sea lice barrier technology reduces sea lice loads on harvest-sized Atlantic salmon with minimal welfare impacts. Aquaculture, 458, 29-37. https://doi.org/10.1016/j.aquaculture.2016.02.014
Walde, C. S., Bang Jensen, B., Pettersen, J. M., & Stormoen, M. (2021). Estimating cage-level mortality distributions following different delousing treatments of Atlantic salmon (Salmo salar) in Norway. Journal of Fish Diseases, 44(7), 899-912. https://doi.org/10.1111/jfd.13348
Walde, C. S., Bang Jensen, B., Stormoen, M., Asche, F., Misund, B., & Pettersen, J. M. (2023). The economic impact of decreased mortality and increased growth associated with preventing, replacing or improving current methods for delousing farmed Atlantic salmon in Norway. Preventive Veterinary Medicine, 221, 106062. https://doi.org/10.1016/j.prevetmed.2023.106062
Worm, M., Bulla, J., Pettersen, J. H., & Frenzl, B. (2026). Control of salmon lice through optical delousing in commercial salmonid aquaculture. Aquaculture, 610. https://doi.org/10.1016/j.aquaculture.2025.742910