In Norwegian Atlantic salmon farming, sea lice infestation is a significant obstacle, drawing widespread attention from stakeholders, authorities, and media alike. Farmers need to manage sea lice outbreaks effectively and, at the same time, keep the welfare of the fish in focus. Consequently, understanding stress dynamics, particularly concerning common treatments like hydrogen peroxide, has become imperative. Hydrogen peroxide, primarily used to combat sea lice and Amoebic Gill Disease (AGD), i s a double-edged sword. While it effectively addresses infestations, its impact on fish stress responses remains less explored. To address this issue, we examined how hydrogen peroxide treatment influences stress responses and the skin proteome and gene expression, shedding light on the underlying mechanisms in Atlantic salmon.
The experiment, spanning four weeks, involved different treatment groups exposed to varying hydrogen peroxide concentrations alongside a control group. Results unveiled a significant increase in plasma cortisol levels across all groups post-treatment, indicative of an acute stress response, particularly at higher concentrations. Notably, the stress response demonstrated a dose-dependent nature, with stronger doses eliciting more pronounced and prolonged responses. Proteomic analysis revealed alterations in protein expression related to structural integrity, wound healing, and immune defence. Concurrently, gene expression profiling highlighted significant increases in genes associated with hydrogen peroxide degradation and immune activation, indicative of an extended stress response lasting beyond 72 hours post-treatment. These findings underscore the interaction between hydrogen peroxide treatment and fish welfare in aquaculture practices. While it proves effective against sea lice, its potential to induce stress necessitates cautious application. Striking a balance between efficacy and welfare considerations remains paramount to ensure the sustainable growth of the Atlantic salmon industry while safeguarding animal well-being.