Gutting a fish, or removing the entrails from its body cavity, may not be the most enjoyable part of the outdoor experience, but should be done as soon as possible after the fish is killed to prevent the growth of bacteria. All fish have virtually identical body structures, so gutting a rainbow trout is essentially the same as gutting any fish. With a little practice, you should be able to accomplish it in under 30 seconds.
Dispatch the fish. Locate the divot at the back of the fish's head with your finger. Hold the fish under the belly with one hand and strike fish sharply, directly on the divot, with the handle of a pair of scissors or the knife handle.
Hold the fish belly up with your hand under the fish's backbone. Insert the tip of the scissors, or the knife balde, 1/4-inch into the fish's rectum and cut along the belly from the rectum to the throat.
Cut through the cartilage strips on both sides of the throat where the cartilage attaches to the gills. Pinch the served cartilage strips between your fingers and pull up and back towards the tail. The entire intestinal tract will usually come out in one piece. Scrape any remaining intestinal matter out of the body cavity with your thumb or the tips of the scissors or knife.
Do not insert the blades of the scissors or knife deeply into the body cavity or you will puncture the entrails.