We use ulu's up north to cut everything from potatoes to fish to seal to caribou. Even the kids use them. They're fairly good at it, too! (this is my nephew cutting salmon with an ulu last week.)
Step 1: What Is an Ulu Knife?
An ulu is a traditional "women's" knife used by the Inuit for hundreds of years. Modern ulu's are made with an old handsaw blade, with a pinned handle on top. The ulu is sharpened only on one side, your thumb side, which helps it cut away from your hand.
I fillet all my fish with an ulu. (Which equals about 300 or more per year)
Step 2: Cut Around the Gills
Use your Ulu and cut around the gills, trying to keep as much of the collar as you can. Only cut on one side, and stop at the fin. Be careful not to cut into the guts at the bottom.
Step 3: Cut Around Backbone and Ribs
Find the backbone with your hands, and carefully use your ulu to cut down the back horizontally toward the rib bones. You will pass the "pin" bones and hear little snaps as you cut toward the ribs. Once you hit the ribs, it's easier, because your ulu should glide right around the rib bones. Angle your ulu down slightly and it will keep the meat on the fillet, rather on the ribs.
Step 4: Cut First Fillet Off
Continue to the belly, and carefully slice the belly off, starting under the mouth, working your way down. Ulu's that are sharpened will glide through the belly, toward the tail. Take your first fillet and place it on the table, flip your salmon upside down.
(If you're careful, you won't have punctured any of the guts, still)
Step 5: Repeat With the Second Fillet
Repeat the instructions on the opposite fillet: Cut around gills, down backbone, around ribs, and off.
Your belly piece will still be on this fillet. You can strip the belly for good smoking later, or you can leave it on the larger fillet.
Step 6: Pull Guts Away
You should be able to easily grab the tail and pull away the bones, guts, and head. We always keep the eggs and most of the female heads to eat, as well. Feel free to keep them. The eggs make great caviar. Our kids like to eat them boiled with seal oil.
Clean your fillets, rinse and pat dry.
Step 7: Eat More Fish!
Your fillets can be vac sealed for later, or, you can smoke, grill, brine, or make into lox.