Ike-jime originated in Japan, but is now used widely in advanced fisheries all over the world.
It is a method of instantly paralysing and causing immediate death of a fish in the most humanely possible way. Any very sharp instrument can be used, but we use a thin piece of round stainless steel rod sharpened to a point.
Upon capture the fish is firmly held still, and the sharpened rod is quickly inserted just above and behind the eye, directly into the brain of the fish. Because every species has a different shaped head, and different sized brain, it takes some practice to insert the spike in exactly the right spot. Immediately on the spike being inserted into the brain, the fish will give a shudder, flare its fins, and then completely relax with all movement entirely ceased. This process takes only a second or 2.
Stress to the fish is minimised with ike-jime, reducing the production of adrenaline. Higher levels of adrenaline will give a slightly more bitter flavour and shorten shelf life of all fish, regardless of how well it is handled.
The energy reserves of a spiked fish are not depleted in the way they would be if a fish was merely bled, or just placed onto ice.
Therefore the fish will enter rigor mortis slowly which reduces tearing of the flesh or flesh tearing away from the bone.
Lactic acid levels will be much lower in fish killed by ike-jime which gives the flesh a slightly less ‘fishy’ taste and slightly softer feel as opposed to letting a fish die slowly.
The blood in the flesh of the fish also retracts into the gut cavity, which results in cleaner, better flavoured flesh. In addition to brain spiking, we also snip the gills of our fish, further reducing blood content of the flesh.
No cuts are made into the flesh of any fish. When exposed to water or air, organic tissue begins to break down much faster than if it was left intact, which greatly affects shelf life. Adding to that, there is very little chance of bacteria entering the flesh.
Freshwater also ruins the flavour of fish.
Whole fish with guts intact is the surest way of ensuring premium quality.