Ecological Impacts and Management of Sea Lice in Salmon Aquaculture

Sea lice infestations, primarily caused by the parasitic copepod Lepeophtheirus salmonis, represent one of the most significant ecological and economic challenges in salmon farming. High stocking densities in sea‐cages facilitate the rapid reproduction and dissemination of lice larvae, leading to elevated infestation pressure on both farmed and wild salmonid populations. Infested wild smolts often exhibit reduced growth, impaired osmoregulation and increased mortality during migration, with cascading effects on fisheries, biodiversity and ecosystem services. The release of vast numbers of infective larvae into coastal waters can overwhelm local predator–prey dynamics, while intensive chemical treatments have driven the evolution of resistant lice strains. In response, a suite of integrated management strategies has emerged, encompassing biological controls such as cleaner fish, mechanical and thermal delousing, fallowing regimes, and spatial planning tools to limit cumulative lice loads. Advances in real-time monitoring and predictive modelling now inform regulatory frameworks that balance industry growth with conservation of wild stocks. Nonetheless, persistent knowledge gaps in larval ecology, host–parasite interactions and the long-term efficacy of non-medicinal treatments underscore the need for continued multidisciplinary research and adaptive governance.

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Ecological Impacts and Management of Sea Lice in Salmon Aquaculture publication trend

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Technical terms

Sea lice (Lepeophtheirus salmonis): Ectoparasitic copepods that attach to and feed on salmon tissue, reducing host fitness.

Traffic light system: A regulatory tool that gauges infestation pressure and environmental risk by categorising regions according to predefined lice thresholds.

Infestation pressure: The concentration of infective sea-lice larvae in the water column surrounding farms or wild migration routes.

Copepodid: The infective larval stage of sea lice that locates and attaches to salmon hosts.

Submersible sea-cage: A farming enclosure designed to position salmon at depths where larvae abundance is lower, thereby reducing infestation.

References

1. Salmon lice biology, environmental factors, and smolt behaviour with implications for the Norwegian salmon farming management system: A critical review. Reviews in Aquaculture (2024).
2. Post-smolt Atlantic salmon can regulate buoyancy in submerged sea-cages by gulping air bubbles. Aquacultural Engineering (2024).
3. Negative association of sea lice from fish farms on recreational fishing catches of Atlantic salmon. Journal of Applied Ecology (2024).
4. Real-time monitoring of cause-specific mortality- and losses in industrial salmon farming. Aquaculture (2023).
5. Sea lice as a density-dependent constraint to salmonid farming. Proceedings of the Royal Society B (2012).
6. Human-induced evolution caught in action: SNP-array reveals rapid amphi-atlantic spread of pesticide resistance in the salmon ecotoparasite Lepeophtheirus salmonis. BMC Genomics (2014).
7. Toward a model-based prediction system for salmon lice infestation pressure. Aquaculture Environment Interactions (2016).