Let me start, while giving my colleague Alistair fair warning that I'm going to ask him to talk on some of the specifics.
I'll start with some sensitivities and assumptions. You talked about what could affect economic viability. We made a number of assumptions. We pointed this out in the executive summary, and the conclusion, and the body of the paper. There are a number of inputs to this that would have a significant effect on bottom-line economic viability. I point to three of them. These affect both closed containment and non-closed containment. I'll start with the price of salmon.
If the price of salmon when we did the study had been what it is today, we likely would have found, even by back-of-the envelope calculations, that the RAS system was not economically viable. When the study was done, the price of salmon was in the range of $2.60. It's now in the range of $2.30. It's gone down significantly. Whether that's because the Chileans have come back into the system because the U.S. market is in tougher shape, or because of the exchange rate, is uncertain. There are a number of factors. But the price of salmon is enormously important. We found in our study that the systems currently being used are economically viable. The RAS system was marginally viable.
Rearing densities are important, those being the number of fish in the pen. We don't have demonstration projects to know how many fish you can stock. So we made some assumptions about how many fish you can put into a pen. We assumed that it would be significantly more than what's in an open-net pen, because otherwise the economics wouldn't be there.
Capital costs are enormous, and a slight change makes a significant difference. You're right to suggest there are serious sensitivities—the price of salmon, rearing densities, capital costs, and exchange rates. As for the specific technical differences between the different RAS-type systems, Alistair can fill you in.