Could I respond to the question that was put?
First of all, there seemed to be some confusion about lice and where they came from, so let me try to clarify that no one denies that lice are a natural parasite of salmon and always have been. As a kid, I'd catch an adult salmon, and it would have lice on it. There is no question about that.
The problem is that we've put fish farms in the middle of a migratory path that wild salmon pass by on their way in, in the summer and fall, and the juvenile salmon pass on their way out, in the spring. In the meantime, these lice build up to large levels on the farmed fish. This is not part of the normal system. In the normal system that cycle would be broken, because the lice would die when the adult fish return to fresh water, so it's not a question of whether they come ultimately from the wild or from the farm. Yes, they ultimately come from the wild, but the farm is basically having a multiplier effect in the system.
Could I also respond to the comment about the controversy, which I began my talk with? I think I may still have a couple of minutes left of that.
You frequently hear people say that DFO studies show that when you put salmon in a tank and you challenge them with sea lice, if the salmon are over 0.7 grams, they seem to mount an effective immune response and they're just fine, so we don't have anything to worry about. My problem with that point of view is that the science involved is not as much wrong as it is totally irrelevant.
Let me do a thought experiment to maybe clarify this for you. Imagine suddenly being deprived of your eyes and your ears. You're blind and you're deaf and you're placed in a room where someone brings you food every day and takes care of all your other needs. You would survive for a good long period of time. Now let's imagine that you are put outdoors, still blind and still deaf, and no one feeds you. There are freeways running back and forth and you have to cross those freeways to get your food. I don't think you would survive for very long.
That's exactly what I think is going on in the wild. We have considerable evidence that juvenile fish that are parasitized by sea lice are far more vulnerable to predation by trout and larger salmonids. These fish don't have time to mount an immune response; they get eaten and removed from the population.
That, I think, is the difference between a laboratory-based approach looking at immune responses and a field ecological approach looking at the actual impacts on the fish in a wild system where there are predators, diseases, competition, and so on.
Thank you.