Whether you have caught a tuna fish yourself or you have just purchased one from the fish counter at the store, the next question is how to slice it up for preparation. Luckily, cutting it into steaks is much easier than it might appear. Cutting tuna yourself rather than buying pre-cut steaks will save you money, while guaranteeing the steaks are cut exactly how you would like.
Place your tuna fish on the cutting board, on one of its flat sides. While tuna are considered to be round fish (not flat fish), they are still flatter on their sides than they are on their tops and bottoms.
Remove the fins and tail, if not already removed. Slide the tip of your fillet knife underneath each fin to ease it off the tuna. Cut carefully so you do not harm the surrounding skin on the fish. Even if you do not want to eat the skin, it will help to hold the steaks together as you cut them. So try not to damage or discard the skin until later in the process.
Consider how many servings you want from the tuna. Consider the overall size of the tuna, and visually divide it up into approximate two-inch sections.
Make the first cut with your chef's knife, easing the tip in and slicing downward, pushing the knife forward and downward from its base. Do not hold it too tightly, and do not make a sawing motion or you will tear the meat. Clean, precise, decisive cutting is what is needed to create well-defined tuna steaks.
Cut the remainder of the tuna fish into steaks. Remove any pin bones with your needle-nose pliers. When possible, pull the pin bones out with the grain of the fish, so as not to disturb the surrounding part of the fish.
Make sure your knives are really sharp before attempting to cut your tuna into steaks. The fins will be more difficult to remove if the fillet knife is not sharp, and if neither knife is sharp, clean cuts will be next to impossible. If you want your steaks to look clean, professional, and beautiful, sharpen your knives.
If your tuna had the head and tail on when you brought it home, you can save those and any bones you find to make homemade fish stock later. If you do not want to use your fish stock immediately, it freezes very well for later use.