SEPA's Sea Lice Regulatory Framework

Annex A: Scientific Foundations

UK Fisheries Act 2020 applied to the development of the Sea Lice Regulatory Framework

1. The Fisheries Act 2020^[5] contains a fundamental scientific principle: management decisions must be based on the best available scientific advice, not perfect knowledge. This approach reflects scientific understanding that regulatory action cannot be postponed by uncertainty whilst acknowledging the inherent limitations of current knowledge.

2. The Act's scientific evidence objective mandates that scientific data relevant to management of [fish and] aquaculture activities be collected, shared between authorities where appropriate, and that management be based on the best available scientific advice. This creates a legal framework that aligns with scientific best practice whilst recognising the practical realities of regulatory decision-making.

3. In environmental sciences, management recommendations are routinely based on incomplete data sets, utilising statistical confidence intervals, uncertainty analysis, and precautionary measures. The Act's framework legitimises this approach in regulatory contexts.

4. The Act defines the precautionary approach as one where "the absence of sufficient scientific information is not used to justify postponing or failing to take management measures to conserve target species, associated or dependent species, non-target species or their environment". From a scientific standpoint, this principle is important for establishing a sea lice regulatory framework because it accounts for scientific uncertainty and knowledge gaps. Primarily these being:

• Population-level effects of sea lice (predominantly Lepeophtheirus salmonis, but also other Caligidae such as Caligus elongatus) on wild Salmo salar (Atlantic salmon, which will be referred to as salmon in this document) and sea trout (Salmo trutta) are inherently difficult to quantify due to multiple confounding factors affecting wild salmonid survival
• Cumulative impacts across multiple salmon farm sites require complex numerical modelling with associated (quantifiable) uncertainties
• Climate change interactions with host-parasite dynamics introduce additional uncertainty layers
• Threshold effects may exist where small increases in sea lice pressure cause disproportionate impacts (“tipping points”)

5. The scientific literature demonstrates that whilst we cannot precisely quantify all sea lice impacts, evidence indicates there is potential for significant effects on wild salmon populations. The Act's framework enables regulatory action grounded on this evidence base without attaining some prescribed level of certainty.

6. SEPA’s framework aligns with the Act's scientific principles of implementing practical risk assessment methodologies. When fully implemented, this represents an application of evidence-based decision-making under conditions of uncertainty.

7. The screening models assess relative risk using available data on salmon farm locations, sea lice levels, and wild salmon migration routes. These models partially account for uncertainty by applying conservative assumptions, and variable post-smolt routes.

8. There is a tiered assessment with an approach that adopts screening for initial assessment, then refined modelling for higher-risk scenarios, optimising inspection and evaluation resource allocation whilst maintaining best possible scientific practices.

9. The framework includes model validation against monitoring data ensuring scientific credibility whilst acknowledging inherent knowledge limitations in complex ecological systems. It aims to be adaptive and encourages regular updates incorporating new scientific evidence, reflecting the iterative nature of scientific understanding and regulatory improvement.

10. Exposure thresholds are established related to on-farm biomass and sea lice counts. This represents a translation of population-level risk into operational thresholds. The scientific basis for understanding the population vulnerability during migration periods reflecting scientific understanding of when wild salmon are most susceptible to sea lice-induced exposure.

11. The risk assessment incorporates proximity to migration routes, reflecting understanding of sea lice dispersal and salmon migratory behaviour.

12. There needs to be an acknowledgement of the scientific limitations in implementing the regulatory framework in that attributing mortality to sea lice remains complex due to multiple pressures affecting wild salmonids, as well as sub-lethal effects such as impacts on growth, condition, immune function, and behavioural impacts. There is a need for cumulative system assessment where multi-site interaction effects require continued model development and validation. There is also the overarching uncertainty of climate change interactions, and with the changing temperature and salinity regimes affecting host-parasite dynamics.

13. The regulatory framework proceeds despite these many uncertainties, implementing management measures based on available evidence whilst maintaining capacity for refinement as scientific understanding advances. The Act's provisions for adaptive management reflect core scientific methodology - hypothesis testing, data collection, analysis, and revision of understanding.

Scientific Assessment of Framework Adequacy

14. From a scientific perspective, the full SEPA framework represents a proportionate response to current evidence whilst maintaining capacity for evaluation. The framework acknowledges uncertainty whilst implementing protective measures based on available data, an approach scientific advisory bodies recommend for environmental management under uncertainty.

15. However, there is a need for transparency, reproducibility and detailed process description for operators and the public, and details of how the framework can be adapted as new evidence emerges. There is also the requirement for defining the refined modelling processes as well as the use of historic data. That is, the framework should be adopted in full.