A Survival Knife isn't the best choice for cleaning a fish but it will perform the job when you don't have an option. If you were in a survival situation with nothing but a fish and a pair of nail clippers, you would sure as hell make it work. So a survival knife is the right tool when your choices are to use what you have or starve.
Scale the fish
Food Chopper
The first order of business is to remove the scales. You will need to put the fish on a flat surface. If you're in a survival situation, you almost certainly didn't pack that deluxe master chef cutting board you purchased from that late night infomercial. So find a nice flat rock or use the ground. grip and hold the tail of the fish firmly, with the tail end close to you. Use the unsharpened or back side of your Survival Knife and scrape the scales off by scraping firmly from tail to head. Once you have the scales removed, turn the fish over and repeat the technique on the other side. A quick rinse in water will clean away any loose scales left on the fish.
Prepare for gutting
Next you need to remove the guts of the fish as cleanly as possible to prevent contamination of the flesh. You will be using the blade side of your survival knife and you need to be careful not to cut in to the intestinal tract or stomach. Get a firm grip on the fish and use your survival knife to make a cut down the length of the fishes belly while holding the fish belly side up. You can start under the jaw at or around the gills and cut towards the vent or anus of the fish, or you can start at the vent and cut towards the head. Be certain that you are only cutting deep enough to slice through the skin. You want your knife to be at a slight angle to the fish when making the cut, so that the sharp edge of the survival knife is on the outside of the fish. You don't want to make the cut with the sharp edge pushing in to the belly and you don't want the knife at a 90 degree angle when making the cut either. That would require you to have surgeon skills, like when you used to play the game "Operation" as a kid. Remember, if you cut too deep you can cut the stomach or intestines open, possibly contaminating the good flesh with fish excrement. Better to have to redo the cut than eat fish poop.
Remove the guts
Now that the skin is cut all the way down the fishes belly, grasp the fish by the head, or belly side up and reach in to the gut cavity. Then simply grab the guts and pull them out towards the vent or anus of the fish. Act like the guts are the peel of a banana. A slimy, less appealing version of a banana peel. At this point you should reach up in to the fishes gut cavity and scrape up and down the spine with your thumb or a utensil like a fork or spoon to remove the blood line or vein. Scrape until it looks clean along the spine. Another quick rinse in water will remove everything you scraped out.
Clean up
You can cut the tail and head off if you wish, or you can leave them on and make believe you are eating at a fancy french restaurant that leaves them on for the presentation effect. You can leave the skin on and make sure you clean out the gutted fish thoroughly with cold water before cooking. You should throw out the unwanted parts (head, tail and guts) away from your site so that you don't attract unwanted guests. Also, when savoring your meal, be careful not to choke on a bone. It hardly seems appropriate to use your Survival Knife to start a fire, build a shelter, catch food and fend off wild animals, only to die choking on a little fish bone because you were too famished to exercise some caution.