As is the case with meat or poultry, cooking fish whole and on the bone adds flavor. Here’s how to fillet it easily once it is cooked.
This is by no means the only method, but it’s a method that works reliably for me. All you need is a fork and a knife. I recommend using a fish knife if you have one, but that is not altogether necessary.
By the way, these pictures are from my recipe for bacon-wrapped stuffed grilled trout. In that recipe, the bacon keeps the fish nicely together and protects the skin on the grill, while lending additional flavor to the fish. However, I use this method with all whole fish.
I pressed a bit hard here and some of the bones (center of photo) came along with the fillet, exposing the herbs. In the best case, this won’t happen to you. However, if it does, simply slide your knife along the fillet to find and remove the bones.