If you think that fresher fish always means tastier fish, you are right but, and I say, but with a big but. I remember my elder brother getting infuriated with my friend, after he told him that aging his fresh Canadian river salmon fish with the guts was foolish. It is true that the proper process of aging fish can actually improve its taste and potential of flavor and more pointedly, “umami”. However, you need to use the correct methodology, and always remove the guts if you intend to age the fish at home.
The technique of Iki jime and its origins are certainly Japanese. I have known about it for over twenty years. I recall telling friends and they seemed stunned about it. Later, I had a friend in Tel Aviv, a capable fish importer named Shalom who introduced me to Leigh fisheries. http://www.leefish.com/LEIGH-FISHERIES-NZ
I received a shipment of their fish and they were exceptional. Lee’s fish is amongst the world’s best on a retail commercial level, and are found in many cities across the globe.
Back to the iki-jime method. It is used to destroy and isolate the nervous system from other organs. Fish generally first circulate blood to the gills, where it is oxygenated. It is then pumped directly to the body system by the heart with the help of the arterial bulb. Reasonable bleeding can therefore be obtained by cutting the artery anywhere, but the usual position is on the gills or the caudal peduncle, at the base of the tail, which is seen in the photo below. In this case a wire is used up the spin to the brain and the fish’s nervous system is paralyzed.
For tuna, both sides of the subcutaneous blood vessels (artery and vein) are cut near the pectoral fins. The object is to destroy the medulla oblongata a part of the brain referred to as the hindbrian (https://en.wikipedia.org/wiki/Medulla_oblongata) responsible for most of the autonomic reactions. Once this is completed the fish is