I don't think we know. Before this issue became so prominent, sea lice on the farms were probably quite a lot more numerous than they are today, with the integrated treatment system we have. I don't think we have any way of knowing exactly where the sea lice are coming from. They've infected the pink salmon.
There are a whole lot of questions that remain unresolved. I'm not casting doubt that they could have come from salmon farms; it's perfectly logical to say that they did or that some proportion of them did. But we don't know about other reservoir populations. We don't know about the winter infection, for example. It seems to begin in December, when most of the wild fish have already come in.
There are a host of issues and questions that aren't resolved. If I'm correct in thinking that the salmon farms now have a good management approach, which means that the sea lice on the salmon farms are very reduced at the time when the young wild fish come out, then I would say we have solved the problem in a practical way, although we still don't understand the dynamics of the situation, with or without farms.