Stingray Marine Solutions

Edit: Farmed Salmon Mortality During Sea Lice Treatment in Aquaculture

Case

Stingray Marine Solutions partnered with the Terravera Foundation to assess how different sea lice treatment strategies influence mortality in farmed salmon and rainbow trout.

The analysis shows that reactive, handling-intensive delousing is consistently associated with elevated mortality in production fish. It indicates that reducing intervention frequency is a key lever for improving survival outcomes in salmon farming systems.

Sea Lice Treatment as a Driver of Fish Mortality

Sea lice are managed through reactive interventions when infestation levels exceed regulatory limits. This typically involves crowding, pumping, and treatment using thermal delousing, mechanical delousing, or medicinal treatment, although physical delousing has become the dominant method in Norwegian aquaculture due to resistance development and reduced effectiveness of medicines.

How Delousing Operations Affect Fish Survival

Scientific studies show that handling during delousing is a key stressor for farmed fish. Thermal and mechanical treatments can cause acute stress during crowding and transport, physical damage to gills, skin, and fins, and in severe cases increased mortality risk.

Outcomes vary significantly between sites depending on fish health, temperature, size, and treatment history, but the overall pattern is consistent: handling intensity is a major driver of biological stress and mortality risk.

System-Level Mortality Patterns in Norwegian Aquaculture

National aquaculture data indicates that over 54.9 million salmon and 3.2 million rainbow trout died during the sea phase in 2025. Mortality remains consistently linked to periods of intensive treatment activity, and fish survival varies strongly with intervention intensity and operational conditions.

Across studies, a recurring system pattern emerges where higher treatment intensity is associated with higher biological losses.

Treatment Intensity and Operational Change

Norwegian aquaculture has shifted toward increased use of physical delousing over the past decade, driven by reduced effectiveness of medicinal treatments, regulatory requirements for low lice levels, and operational need for rapid intervention. This has increased the frequency of handling-based interventions across production cycles.

Terravera data modelling

What is being modelled
Mortality risk in farmed salmon linked to sea lice treatment operations.

What the model actually does
The model links treatment frequency and handling intensity during delousing to mortality outcomes, using published effects from thermal and mechanical treatment methods and scaling them across production systems.

Core comparison
High-intervention, handling-intensive treatment systems versus reduced-intervention systems enabled by continuous in-pen delousing.

Output
Estimated treatment-attributable mortality burden across production cycles.

Continuous Optical Delousing as an Alternative

Stingray’s optical delousing system uses cameras, machine learning, and laser technology to detect and remove sea lice directly inside salmon pens. The system operates continuously and without handling, reducing the need for crowding, pumping, vessel-based delousing operations, and repeated intervention events.The analysis indicates that reducing handling intensity may lower mortality pressure across production systems.

System Implications for Salmon Farming

Terravera’s modelling shows that sea lice management directly affects fish survival. The findings indicate lower mortality risk when handling is reduced, reduced biological stress across production cycles, fewer intervention-driven mortality peaks, and more stable production conditions.Overall, the results point to a shift from reactive intervention systems toward continuous prevention models with lower biological cost.

Terravera System-Level Modelling

Terravera provides system-level modelling that translates aquaculture operations into comparable biological impact metrics.For Stingray, this enabled assessment of how different sea lice control strategies influence mortality risk, handling intensity, intervention frequency, and system-wide biological pressure.The modelling helps quantify how sea lice management strategies affect both operations and biological outcomes across aquaculture systems.

  • Veterinærinstituttet, "Fish Health Report 2024," Veterinærinstituttet, Tech. Rep. Report 1a/2025, 2025. [Online].

  • Fiskeridirektoratet, "Biomass statistics by production area," Accessed: 2026-01-24. [Online].

  • H. McKay and S. Shah, "Mapping salmon welfare: Sea lice treatments," Rethink Priorities, Nov. 2025. [Online].

  • C. Sviland Walde, B. Bang Jensen, J. M. Pettersen and M. Stormoen, "Estimating cage-level mortality distributions following different delousing treatments of Atlantic salmon (Salmo salar) in Norway," Journal of Fish Diseases, vol. 44, no. 7, pp. 899–912, Jul. 2021. doi: 10.1111/jfd.13348

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