"I have been pan frying trout over campfires for years on fishing trips with my dad. It works great."
I did the same for many years, but quit for a variety of reasons. It is easy to do, but requires a lot of wood to fry up a decent mess of trout. I carried a paper bag of flour seasoned with salt and pepper and shook the trout(whole if small, or pieces if from larger fish) in it to coat them, then fried them until the skin was crispy brown. Ummmm, good, skin, tail, head and all. As a second course, I added rehydrated mashed potatoes seasoned with garlic and spices to the pan drippings, spread it out to make a pancake, and fried until brown on both sides(flipped once, just like a regular pancake). You could also do this with a canister stove, but it would also take a lot of fuel. As for boiling, not so much, if all you do is boil the fish in plain water. A better method is to use any of a number of Asian noodle soups, add pieces of fish 3-4 minutes before adding the noodles, dependiong on the size of the pieces(just enough time to poach them and not until they turn to mush). The fish makes a great addition to the noodle soup and also provides extra protein for your meal. You could do this wwith straight Miso, too, if you wanted a simpler soup. Or chicken bouillon.