I have cooked a lot of fish on a stove and it is so variable that you could not come up with an exact time to cook or heat setting. A 8-inch pan full of fish takes at least 4-5 minutes on med-low heat. Depends on how willing you are to eat fish cooked rare. It is critical to have a pan with a tight lid. You basically steam the fish and then if you want a crispy skin, take off the lid the final few minutes. You can save a bit of fuel if you have a larger heavier fry pan, but then the extra weight of the pan is more than the fuel. Tiny fish are a pain to eat (pick out bones) and big fish hard to cook. I do best with medium size (about a fat 10-inch trout), cut in half, tails and heads removed. I actually do not mind taking extra fuel for fish- if I do not catch fish I can have lots of extra hot drinks. Fuel is never "wasted". Hot water to wash my face is a real luxury.