Now that you have caught your fish, you have to clean it. There are several ways to clean a fish. Always wash the fish first with cold running tap water. Avoid using the lake or river water if possible. Also, try to clean the fish as soon as possible after removing it from the water to avoid excessive bacterial growth.
The first and easiest way to clean a fish is to lay the fish on its side and using a sharp knife, cut from the gills through the backbone. Then when you snap and pull on the head, the entrails will just follow. Then cut along the belly of the fish from the gills to the vent (the small anal opening near the tail). Inside the fish, scrape along the backbone to remove the blood vein. Then rinse the fish thoroughly with cold water. If you wish, you can just cook the fish with the skin on it until the skin begins to peel away from the flesh. Easily remove the skin and the dorsal fin will follow.
The second way to clean a fish begins by rinsing the fish using cold tap water and then de-scaling it. Not all fish need to be de-scaled. To determine if your fish needs to be de-scaled, lay the fish flat and with the dull edge of a knife, at almost a 90-degree angle to the fish, use short strokes moving from the tail to the head. If the scales are large and flat, then they should be removed. Keep removing them until the fish is smooth. Repeat on other the side. Note that if you are planning on skinning the fish before cooking, then this is not necessary.
Next, with a sharp knife, cut from the gills along the belly to the vent. Open up the fish and remove all of the entrails with your fingers. Then scrape along the backbone, using your thumbnail or spoon, to remove the blood vein. Wash the fish thoroughly again using cold tap water. If you are planning on cooking the fish whole, it's a good idea to remove the dorsal fin (top fin) next. Just cut along both sides and pull using a pair of pliers. Rinse the fish one last time.
For your safety, always use care when using sharp knives. Also, when storing fish in a cooler on ice, be sure that the fish is not allowed to sit in the melted ice water. Allow the water to drain away from the fish, and keep the fish with its cavity facing down so that melted ice will not pool inside the fish. Never store the fish for prolonged periods of time. Notice that fresh fish does not smell fishy. As fresh fish gets old, it gets the fishy smell. Use this as an indicator of whether your fish has become too old to eat.