Temperature-driven suitability shifts of sea lice species under climate change and the implications for salmon farming

Salmonids are the most valuable marine aquaculture family, worth approximately US$26.2 billion in 2022. However, the industry’s economic value is threatened by sea lice infestations, which can cause production losses and require expensive treatments to control. Climate change is driving distribution shifts in many marine species, including a potential poleward movement for several parasites. Currently, only the distribution response of the Chilean sea louse Caligus rogercresseyi has been examined under climate change conditions, while other harmful sea lice species remain unassessed. Here, we use a maximum entropy model to project the current and future thermal suitability of Lepeophtheirus salmonis , C. elongatus, and C. rogercresseyi under 3 climate change scenarios: SSP1-1.9, SSP3-7.0, and SSP5-8.5. The species’ thermal niches are similar, with preferred mean temperature ranges of 7.1 to 11.1°C for L. salmonis , 6.8 to 11.9°C for C. elongatus , and 11.0 to 12.8°C for C. rogercresseyi . Thermal suitability for all 3 species shifts and intensifies polewards under progressively warmer climate scenarios. As ocean warming also facilitates poleward range shifts of many salmonid species, the overlap in host and parasite distributions indicates that salmon aquaculture at higher latitudes could face increasing lice infestations and associated challenges.