Cut off the head and pull out the organs. Tie a rope around the tail and hang it up out of the sun. Blood in meat generally tastes bad. A salmon spine can't take the force of being held by the tail without breaking, so make extra sure to bleed the fish if you intend to hang it. This is a red salmon after a day of hanging. Some people will just throw the fish on top of the cabin in the shade, but hanging it helps get more blood out.
Filleting a fish is generally easy if there is a head to hold on to, so hanging can make the fish hard to fillet. Maybe that means it's time to get a cleaver and do steak cuts.