If you need to gut your fresh catch of the day, all you need is a pair of chopsticks. Warning: You will literally see a fish's guts get yanked out of its mouth.
This gutting method, demonstrated in the video above from the Morigami YouTube channel, removes fish innards and gills without forcing you to cut it open or remove the head. Take a pair of throw-away chopsticks and insert them into the fish's mouth past the gills, give the chopsticks a few hard twists, then slowly pull out the innards through the mouth. Rinse the inside of the fish with water and it's ready to be cooked or frozen for later use.
This fish cleaning method is known as the "tsubo-nuki" technique in Japan, and is popular throughout many parts of Eastern Asia. It's ideal when you're serving fish whole or just tossing them on the grill because the body stays intact and keeps its shape nicely while cooking. You also avoid accidentally cutting into the fish's digestive tract or other organs that may require additional cleaning of the fish.