Shinkei nuki: destroying the spinal cord with a wire
Shinkei nuki is passing a wire down the spinal canal to destroy the spinal cord after the brain spike. It stops the post-mortem nerve signals that keep depleting energy stores, which delays rigor and extends freshness.
What it does
Even after the brain is destroyed, the spinal nerve keeps firing post-mortem and keeps depleting the muscle's energy stores. Shinkei nuki, or spinal-cord destruction, ends that activity by running a wire the length of the spinal canal. The result is delayed rigor and extended freshness.
How to do it
Pass a shinkei or nerve wire down the spinal canal, entering either through the brain spike hole or through a cut made at the tail. Work the wire back and forth to destroy the cord along its length. When the cord is struck you often see the body flex or twitch in response.
When it is worth it
This step is optional but powerful for premium fish, especially any fish you plan to age. For quality table fish it can meaningfully extend how long the flesh stays at its best. For a fish you will eat the same day it matters less than the brain spike and bleed.
FAQ
Do I enter from the head or the tail?
Either works. You can pass the wire through the brain spike hole or through a cut at the tail, whichever gives you a cleaner line into the spinal canal.
How do I know the wire is in the spinal canal?
You feel it track straight down the canal rather than into flesh, and the body often twitches as the cord is destroyed. If it jams or veers, withdraw and reangle.