In search for the most humane ways to kill a fish, I have came across the technique Ikejei. This is said to be one of the best methods to preserve the quality and flavour of a fish.
From what I got, the technique consists of more than killing the fish fast. After killing the fish, there's a not so simple procedure for bleeding it by cutting the fish in the gills and in the tail and then, another procedure, of cleaning the blood inside the spine.
Regarding the cuts, I know that in the gills one should cut completely the area that connects the gills and the branchi operculum.
However, one question remains, how to effectively hit the entire central nerve of the fish's spine with a "streak"?