Sea lice are ectoparasitic crustaceans that reduce the somatic growth and food conversion efficiency of farmed salmon resulting in substantial economic losses. Treatment methods include chemotherapeutics administered in-feed or as a bath, cleaner fish, or harvesting the salmon and having the farm remain fallow before restocking. The population biology of sea lice depends on temperature-dependent maturation rates and salinity-dependent mortality rates and egg production. We derive a stage-structured delay differential equation model with periodic temperature and salinity to understand sea lice population dynamics. We numerically calculate threshold conditions for sea lice growth and compare model predictions using environmental data from salmon farms on the east and west coasts of Canada. We add chemotherapeutic treatments into the model and validate model predictions against sea lice abundance data. As such, we develop and test a model describing the population biology of sea lice that will serve as a foundation for future work to characterize optimal sea lice treatment strategies.

Co-authours: Matthew Rittenhouse, Marty Krkosek, Crawford Revie, Xiunan Wang and Xiaoqiang Zhao