Looks like he went all the way forward through a gill net...Look carefully at the bottom of mark #3 from the front. It looks Like an upsidedown "y"with a slight oblong dot where the Y comes together then at the top a nother line coming in like this >. Those marks are consistent with nets. The large superficial bruising is caused by the fish forcing his way through the net and the constriction. I'm glad your brother caught that fish as the wounds are pretty deep and probably would have been sturgeon bait around bonneville.