1. Much of the information publicly available is from Norway, and that is the case because Norway is the only salmon producing country where all delousing events have to be reported to the Norwegian Food Authorities after which they are made publicly available; however these data present many uncertainties (Overton et al., 2018).
2. Where: red bordered rectangles represent different types of management measures; blue bordered ovals represent inputs and their production processes; purple bordered ovals represent outputs; bold blue and purple arrows represent material and energy flows; red arrows represent relationships between the management measures and production inputs and outputs. These are elements of the LCA model and Figure 1 shows both flows and influences included in the model.
3. This method is now only very infrequently employed on Scottish salmon farms, however we have included it in the analysis for comparison purposes.
4. The prices used in the analysis (mostly for years 2013/14 and 2017/18) were comparable. Price standardisation was not considered and testing for nominal values of other variables e.g. sourced for the LCA analysis feeding into CEA was performed using sensitivity analysis.
5. CLDs are a combination of different feedback loops that exist within a system. Feedback loops can be either reinforcing or balancing. Combinations of these loops state the specific behaviour of a system over time (K. Rich 2018. Causal loop diagrams for systems thinking. Training notes).
6. Notations in the CLD:
7. R - a reinforcing loop reinforces behaviour in a system, either leading to a virtuous or vicious cycle.
8. B - balancing loops which, by contrast, counteract and resist change. In a balancing loop, the system converges on a target.
9. CLD was created using Stella Architect software by ISEE Systems, 2016
10. ± signs on arrows: links move in the same direction (denoted by +); links move in opposite directions (denoted by -)
11. Most variables also have an indirect influence on many other variables as shown by sequences of effects (arrows)