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Now reading How to Perform Ike Jime

How to Perform Ike Jime

The traditional Japanese fish-killing process, and why it makes your fish taste better.

This story comes from Lucky Peach #2: The Sweet Spot. For more great stuff like this, subscribe to the magazine!

Normal Long Island fishing practice dictates that when a striped bass gets pulled aboard a boat…

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you whack it with a billy club…

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slit it under the gills…

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and throw it into a cooler full of ice. 

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The live fish is now a dead fish; the fishing poles go back in the water. The results are good—I grew up on fish caught and killed like that.

Japanese fishermen who are serious about the quality of their catch approach the process of killing fish differently. Rather than whacking their catch, they insert a spike into the brain and then quickly bleed the fish out. It’s a method called ike jime. Some argue that it’s more humane; all I know is that the next time I was on the water after I saw a video of how to do it (brought back from Kikunoi restaurant in Kyoto by the Lucky Peach team), I tried it out. And the results—the flesh is much firmer and more flavorful—were undeniable and spectacular. Other fishermen give me weird looks when I sing the praises of ike jime—fishing is a bastion of tradition here in Long Island—but the payoffs on the plate are hard to argue with.

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1. As a fish fights against being reeled in, it produces lactic acid in its muscles. How much lactic acid depends on a range of factors—the distance and depth the fish is reeled up from, the water temperature and power of the current it’s fighting in—but it’s safe to assume that an exhausted fish reeled onto the deck of a boat has muscles burning with lactic acid. Ike jime, unlike most fishing practices, considers the effect of lactic acid on the taste of the meat. (To defend my native territory, I will note that I have read about Long Island fishermen who catch giant bluefin tuna, get them to the boat, put them on a stringer, and drag them through the water for a few miles so their bodies relax before being dealt the coup de grâce.)

These pictures are from a trip we took in Montauk. After landing a few striped bass, we got the fish aboard then took a needle and punctured the swim bladders—the gas-filled organ located on the belly side of the fish, about two inches behind the end of the gills on a striped bass—just as I had seen Chef Murata do in the video from Kyoto. When you horse a fish in too rapidly from deep water, it doesn’t have time to adjust the amount of air in its swim bladder. This isn’t good for the fish or for its future on the plate, ike jime or no—the bladder expands because of the pressure change, and after a certain point it damages the organ around it.

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2. Once we punctured the swim bladder, I immediately put the fish in a live well—a tank of seawater with a circulator pumping fresh air into it. I gave the fish sixty minutes to mellow out and recover, and to allow the lactic acid in their muscles to dissipate. In Kyoto, they let fish sit in a small cage within a tank (where it is basically immobilized, but still very much alive and breathing) for twenty-four hours, which probably enables even greater dissipation. But they’ve been doing this for hundreds of years, and I was working with an improvised rig on a rented boat.

Once the fish were rested, we removed them from the tank and placed them on a cutting board. I then delivered a blow to the top of each fish’s head with an improvised “brain-spike tool” (a shortened gaff hook on the end of a wooden shaft). I aimed for a spot about two-and-a-half inches back toward the dorsal fin, directly in line with the midpoint between the eyes. (I’d dissected a striped bass bought from the market the night before to find the exact location and size of the brain, for reference.) If you hit the right spot, the fins will twitch, extend, and then freeze; the mouth will open; and the animal will stiffen.

If one of the fish didn’t immediately adopt that stunned look, with its mouth wide open, I carefully twisted the hook to try to scramble the brain. After the “brain spiking,” I lifted the gill plate on each fish (the bony area just in front of the gills) and looked for the spine. I then identified the small gaps between each vertebra (those gaps are the softest area of the spine), and did my best to aim my knife and slice through one of them. If you get it right, the fish will start bleeding instantly and profusely, and it will also stop breathing. (You can tell because the gill plate won’t open on its own anymore, and the fish will no longer look like it’s gasping for water.)

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3. As soon as I was sure I’d severed the spine and cut the main blood vessel of each fish, I made my way down to the tail section. About two inches from the beginning of the tail, I scraped my knife up against the scales, toward the head of the fish, to remove a small patch, creating something like an access panel. Then I sliced through the flesh until I hit the spine. Once I’d done that, I gave the top of the knife a firm tap with my fist to push it just through the spine, stopping short of going all the way through the flesh and skin on the opposite side. On a larger fish, this might need some extra encouragement from a rubber mallet, because the spine can be extremely thick.

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4. At this point, if you fold the tail under the fish and wipe away any blood on the flesh, you can expose, by way of your “access panel,” the two canals that run alongside the spine. The bottom canal is a major blood vessel. The canal on top of the spine (closer to the dorsal fin) is the neural canal, which is filled with fluid and runs the length of the fish. This is the one you’re interested in.

What you want to do is thread a thin but stiff wire directly into that canal and push it toward the head. The muscles in the fish will spasm, and the fish will flop a bit. As soon as you’ve reached the brain, the wire will hit a hard blockage and not go any farther. Now the fish is not only dead, but you’ve destroyed its nervous system, which lets you short-circuit the more aggressive and damaging effects of rigor mortis.

To finish, slowly remove the wire and put the fish in a large cooler full of seawater, along with a shovelful of crushed ice to cool the fish down and allow it to finish bleeding out. It’s important, at this point, that the tail doesn’t flop over and clamp off the severed main blood vessel, so with each fish I zip-tied the tail to the body. Then I allowed the fish to bleed for an hour or two, changing the water frequently and adding ice as it melted. After that, we packed the fish loosely on flaked ice, with guts intact.

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5. Generally, you can expect to wait eight to ten hours after a fish has had ike jime performed on it for the fish to come out of rigor mortis. (For a larger fish, this can take as long as three days. My nearly thirty-pound bass took forty-five hours.) Once that’s happened, you’ll want to scale and fillet the fish, taking care not to puncture its internal organs. Place the fillets into a cooler with an ice block—not a refrigerator, as the fan will dry out the flesh. Then, when you’re ready to serve, slice the fish as you would for sashimi or hwe (Korean-style thinly sliced raw fish) on an extreme bias perpendicular to the grain, and enjoy.