The salmon farming industry is crucial to meeting the growing global demand for protein, generating employment, and strengthening the Norwegian economy. However, balancing economic growth, animal welfare, and environmental protection is a complex challenge. To achieve this, in 2017, Norway implemented a rigorous regulatory system, including the Traffic Light System (TLS).
The Traffic Light System (TLS), known as the Sistema de Semáforo (SS) in Spanish, is a tool to manage salmon aquaculture and mitigate the impacts of sea lice on wild salmon. This system uses observational data and models to assess the risk of negative impacts on wild populations. However, a recent comprehensive analysis has questioned the effectiveness of the TLS.
A team of researchers from Marine Prospects AS (Norway), the University of Bergen (Norway), and Fisheries and Oceans Canada published a scientific review in the journal Reviews Aquaculture. The review covers the literature describing the biology of salmon lice, environmental factors, and salmon behavior relevant to the accuracy and reliability of the Traffic Light System (TLS), providing value to the expert community, policymakers, and managers.
The Sea Lice Challenge
Sea lice, a natural parasite of salmon, have become a significant threat to aquaculture and the survival of wild salmon. Their economic impact and the welfare of farmed fish are evident, raising concerns about the conservation of wild populations.
How Does the Traffic Light System Work?
The TLS, introduced in 2017, divides the Norwegian coast into 13 production areas. Based on estimates of wild salmon mortality caused by lice from aquaculture, each area receives a risk classification: green (low), yellow (moderate), or red (high). These categories determine the salmon production limits in each region.
Since directly measuring the impact of farm lice on wild salmon is impossible, the TLS relies on observational data and complex models. These include lice counts on wild and farmed salmon, as well as models estimating lice density, dispersion, and infestation.
Challenges and Opportunities
Although the TLS is an important step towards more sustainable aquaculture, it faces challenges. The accuracy of the models depends on data quality and our understanding of sea lice biology and salmon behavior. Additionally, environmental factors such as water temperature and ocean currents influence lice dispersion.
Researchers identified the following critical flaws in the pillars of the TLS:
- Incorrect infection pressure estimates: The system assumes incorrect dates and durations for the migration of young salmon, leading to unreliable observational data and models, and overestimating infection pressure.
- Inflated larval production: The number of sea lice larvae produced by farmed salmon is being overestimated.
- Questionable data: TLS models rely on or are calibrated with the same potentially flawed data, compromising their accuracy.
- Exaggerated mortality: Wild young salmon mortality caused by sea lice may be overestimated.
- Lack of correlation: Lice infection levels on farms are not associated with measurable effects on wild salmon.
Improving the Traffic Light System
To increase the accuracy and reliability of the TLS, and hence its environmental efficiency, the following measures are proposed:
- Incorporate more variables: Utilize available biological and physical environmental variables more comprehensively.
- Adjust analysis periods: Modify the time period for recording observational data and integrating modeled data.
- Recognize uncertainty: Interpret data considering uncertainty in model results.
- Adjust mortality thresholds: Use more realistic assumptions about lice-induced mortality thresholds.
Implications for the Salmon Farming Industry
The new study casts doubt on the effectiveness of the Traffic Light System (TLS) used in Norway to regulate the salmon farming industry. This system, designed to protect wild salmon from sea lice, appears not to be delivering the expected results.
The research reveals several critical points:
- Factors beyond farm control: The study found that factors such as young salmon behavior, ocean currents, temperature, salinity, and possibly predation significantly impact sea lice infestation levels. This suggests that salmon farms are not the sole contributors to the spread of these parasites.
- Incomplete model: The TLS does not adequately consider these external factors, limiting its precision in predicting risks to wild salmon.
- Discrepancy between theory and reality: TLS predictions about the impact of aquaculture on wild salmon populations do not match real-world observations. This raises serious doubts about the system’s reliability.
In summary, the study concludes that the TLS needs to be improved to more accurately reflect the complex reality of marine ecosystems and ensure effective protection of wild salmon. It is necessary to incorporate more variables into the models used and continuously validate the results with real-world data. Only then can we ensure a sustainable balance between aquaculture and nature conservation.
This finding is crucial for rethinking the management strategies of the salmon farming industry and ensuring the survival of an iconic species like wild salmon.
Contact
Albert Kjartan Dagbjartarson Imsland
Akvaplan-niva, Iceland Office
Akralind 6, 201 Kópavogur, Iceland.
Email: albert.imsland@akvaplan.niva.no
Reference (open access)
Dagbjartarson Imsland, A. K., & M. Jones, S. R. Salmon lice biology, environmental factors, and smolt behaviour with implications for the Norwegian salmon farming management system: A critical review. Reviews in Aquaculture. https://doi.org/10.1111/raq.12953
