On a 2-3 day trip, I would be willing to leave behind 1/3 of my food - in other words be willing to go hungry one day if I caught no fish. I often walk back to my car on the last day of a backpack with no remaining food. However, be sure you are going in an area with known good fishing. If I am exploring lakes to see if there are fish, I do not depend on catching any.

Last summer we did an 11-day trip (no rest days) in the Wind Rivers and caught all the fish we wanted every day and walked from about 8AM to 4PM every day. You still need a bit of carbs with the fish - instant potatoes or cous-cous are good and light. And be sure to take oil for cooking. Also have a good spice kit because plain fish every night for 11 days gets really boring. I cut down our ration from the usual 1.5 pounds per day to 1 pound per day per person. However my husband, who is not as keen on ANY probability of missing meals, added some trail bars and "goo" for his comfort. He made it clear that he was not going to share these goodies if we could not catch fish! I took only fly fishing gear and he took only spin gear. Between the two of us, we always caught fish. He would troll for the big fish (about 14-16 inches - two of these fish were all we needed). If he had no luck, I would go out and catch enough small fish to fill the frying pan.