Sure. The floating closed containment system is completely enclosed except, obviously, for the opening at the top. It's like a bathtub, but when it draws the material out of the bottom, it takes it into a separate area where the water is separated from the solids. The water is then returned to the ocean, but only after the solids have been removed. Of course, the solids include mortalities and things like that.
There's no way for the fish to actually get out of the solid wall. In fact, they have fences around the top and a netting over the top so the fish can't even jump out, if they were inclined to do so. So it will keep the salmon that are in the closed containment system separated from the wild salmon.