On a bigger northern, when you take the fillet off lay it shin down. About a third of the way down from the top you will see a row of white dots, the ends of the "Y" bone. I use a long sharp fillet knife.
1. First cut is right along side the row of dot downward until you hit where the bones "Y" then turn the knife and follow the bones til they end.
2. Do the same on the other side of the dots.
3. At the end of the short side turn the knife and cut just under the bones, you should be so close to the bones you can see the knife blade through the bones. Just follow the underside of the bones until you meet up with your first cut.
4. The whole row of bones will lift up and away with virtually no loss of meat.
5. Remove the skin as usual. It helps to leave the skin on until the bones are out as it stabilizes the fillet to work on.
Nice to have a fish that helps you do the work. "Just cut on the dotted line"
Here's a short clip that will show how the bones come out.
https://www.bing.com/videos/search?...ED2363E2EE7A0894B89&&FORM=VRDGAR