I suppose if you're limiting this discussion to commericially harvested salmon, then I would agree with Salmo's line of thought. I have worked on a catcher processor (between college) that drag's the bottom for cod. Those things drug up everything on the bottom, bicatch was huge and it was utterly disgusting. While the gill netters may be able to target species more so than purse-seigners and definitely more that the dragging fleet, they still must get bicatch (haven't worked a commercial salmon boat).