Ike Jime Part 2 – What “closing” does to the fish?

Why Ike Jime closing is needed

Let’s look at the 3 steps of Ike-Jime closing more closely and see why we do this.

Closing Fish Immediately

The instant treatment is essential. DO NOT let the fish suffer. When the fish suffers, like slowly drowning in the air, there’s a chemical reaction in the muscles. Stress is not just an emotion. Stress eats up the energy source and chemical compounds within the muscle cells which make us feel “tasty”. Stress also leaves fatigue components like lactic acid and ammonia within the meat. The recent study shows when the fish suffers to death, the chemical reactions in the meat speed up to decomposition. That also means that the tasty period for the meat comes and goes very quickly.

Some people keep the fish alive in a bucket. The intention is probably to keep the fish as fresh as possible, but this is the worst thing you can do to the fish actually. The suffering lasts longer. The meat will be tasteless, soggy, and quick to go rotten. Fishing boats have fish tanks where the fresh sea water comes in and out. This is much better than a bucket. But if you mean to eat the fish, better close it immediately.

Breaking spinal cord

What this treatment does is to isolate the muscle “off-line” so that it wouldn’t know that it’s dead. This treatment slows down the breakdown process. resulting in tasty period lasting longer, giving more time for the aging process.

In several hours after fish dies, it experiences the whole body contraction, called rigor mortis. Even after death, the muscles keep looking for energy source but there’s no blood supply or no oxygen. So they start consuming the savings of energy within the cells, called ATP. ATP decrease changes pH and results in the whole body contraction. When ATP is all used up, the muscles literally die. That’s when the body is the most rigid, the state of rigor mortis. After this, the body starts loosening and the proteins start breaking down to amino acids and then eventually to decomposition.
By breaking the spinal cord, you kind of set the meat into sleep. It slows and calms down the break-down process in a way we call “aging”.

Draining Blood

Blood is bad. Blood is where the fishy odor comes from. Blood is what incubates all the bacterias. Don’t wait. Drain completely as soon as you close the fish.
If you wait, blood will get in the meat and that’s the end. The meat will soon get smelly, look dark and go rotten.

Close first or drain first?

I have discussed this with my fellow anglers. He insisted that we should drain first while the heart is still pumping for maximum blood draining. It seemed to make sense to me. But I still have a little doubt. I did some looking-into and found a research study by Marine Net Hokkaido.


Method A: Drain blood
Method B: Ike-Jime closing
Method C: Ike-Jime first and drain

Red graph on left shows the amount of blood draining. Blue graph on right shows the amount of ATP remaining

When you just cut a gill and drain blood, you can drain the most blood but you will get the least ATP left. Apparently the stress will eat up ATP. It seems best to close first, let the suffer stop, and then drain blood.

Ike Jime makes a difference

Look at the picture of the fillets of flounders below. Left has suffered to death from being left in iced water. Right has been Ike-Jime closed. This is the picture 48 hours after closing.

It is from a research project by Hokkaido University in 2012. As you can see Ike-Jime does make a remarkable difference. Suffered fish looks dull with blood spreading in the meat. Can be smelling by now. The meat can be soggy and collapsing. Closed fish looks clean, bright, and solid.

Aging Process

Let’s look more closely at the aging process.

The proper closing, Ike-Jime, and proper storage makes the aging period longer. There’s more time before decomposition, so the meat can sit to mature and develop Umami components for rich flavor.

Umami comes from the Japanese word, a savory taste, now recognized as one of the 5 basic tastes with sweet, bitter, sour, and salty. Our tongue has receptors for L-glutamate. These amino acids in various foods are what Umami taste is based on.

Below is a chart of the aging process. It depends on what fish how fast the aging process progresses. Some are fast and some are slow. Even the same fish is different by the location, by the season, and by individuals. But proper closing maximizes each fish aging period.
Good sushi chefs senses the individual conditions and controls the aging process, and serve each fish at the right time.
The chart shows the process but the time frame is just a general idea. It really depends on various factors.

Phase 1: Right after closing (within 3 to 9 hours)

The meat is definitely fresh. The meat is translucent and beautiful. But the texture is still tough, lively, sometimes too gummy and chewy. Because all the fibers and the structure of the proteins are still in a good condition. And the taste is plain, as no Umami components haven’t been produced yet.
Many people still believe that the fish is at its best right when it’s dead. But this is not very true. It’s like immature fruit.

Skipjacks and Bonitoa are exceptions
The fish tank is merely for LIVE entertainment

Phase 2: Toward rigor mortis (within 9 to 48 hours)

When ATP is broken down, it leaves IMP, inosinic acid. This is a Umami component. At rigor mortis, ATP is all gone, meaning that the meat is full of IMP at maximum. On rigor mortis, the body gets rigid but the meat itself is not tough actually. It’s solid and elastic, but soft to chew.
This is one of the best time to eat. The taste is moderately developed with IMP and the texture is still fresh. Amberjack, halibuts, and the kind of fish that you enjoy the texture of, are at their best here.

Phase 3: Post rigor mortis (within 2 to 5 days)

Once passed the rigor mortis, the meat starts loosening and IMP starts decreasing. But the decreasing pace is slow if the fish has been closed properly.
The other aging process starts taking effects here. The protein has been breaking down by its own enzyme to amino acids and peptides, all Umami components. Especially IMP and glutamic acid combined is a unmatchable Umami.
This is the tastiest period. The taste is rich, even though the texture is a bit softer. Most fish is good here. The kind of fish that is too chewy in Phase 2 would be beautiful to have at this point.

Small Mackerel family should be eaten or heated by this time. Because they are full of unsaturated fats. So good for your health but bound to go bad quickly.

Phase 4: Toward decomposition (within 5 days to 1 week)

The texture has become much softer. The aging continues. Umami develops more and more. The flavor becomes full-body often with a quality of sweetness.
The surface might change to darker color due to oxidation. But the quality is the same. You just need to slice off the surface if you want to have it look good.

A big tuna over 30kg can last over 1 week. They let a 300kg tuna age up to 20 days.

Chewy meat like cods and groupers, sometimes snapper, is at its best around this time if you like rich aged flavor.


They say food is at its best just before decomposed. Do you believe that? A lot of times I find it true. But I’m talking about eating raw fish that you caught several days ago. And I’m an amateur. I’m just sharing what I and many Japanese anglers do. But you just need to be aware that you are walking on a thin line here. You need to be careful with your own responsibilities. Use your own senses. And always play safe.

You will appreciate the difference even when you cook the fish. Not as much as sashimi of course. But the closed fish smells better and tastes better. Before you might have thought that you should freeze the fish within 2 days, but now you don’t have to for a couple more days.

My sashimi preferences

Here is the list of my personal sashimi preferences, on the assumption that the fish has been properly closed and stored on my own responsibilities. Just to give you an idea what Ike Jime can do to each fish.

Fish Day 1 Day 2 Day 3 Day 4 Day 5
Small Tuna Good Good OK
Bonito Good Great OK
Medium Tuna Good Great Good OK
Trevally Good Great Good OK
Amberjack Good Great Great Good OK
Snapper OK Good Great Great Good
Grouper NO OK Good Great Great
Example With A Grouper

Look at this grouper fillet. It’s Day 6. Beautiful meat with translucent quality. Still looks good for sashimi, but it’s a cold night and we are doing fish soup.

It was caught on Wednesday. It was my first fish of that day around 8am. I think it’s Epinephelus cometae. About 40cm, 1kg.

Ike JimeIke jime closing. I always do it like this. Sandwich the fish with the soles of my shoes, and put in the wire along the spine. I see the target line more clearly this way. Then it was laid in a cooler box, in the plastic bag on the ice for a whole day on the boat. When we were back in the evening, the fish body was not stiff yet, soft like live. Then I scaled, gutted, and filleted that night. Wraped it with a paper towel which sucks out the liquid but stays dry on the contact side, no plastic wrap, and put it in the fridge.

This is Day 6, Monday night. I made the base from the head and the bone, which has been frozen, along with Kombu. Cook the fillet with vegetables and tofu in the soup base. It was fabulous. The texture was still intact, a little softened but the grouper meat is pretty firm to start with anyway, it was a perfect texture. The taste was so rich. Full of Umami.

I hope you find this article informative and helpful to you!

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  1. Kitidas Punyashthiti
    Kitidas Punyashthiti12-06-2012

    Hi Totos,
    Could you add the definitions of ATP and IMP, this would make this article more complete. I really appreciate your effort in sharing such an art of handle the fish which is hardly known to the outside. Thanks again and best regards,
    Kitidas P.

    • Totos

      Hi Kitadas,
      Thank you very much for your compliment and feedback.
      I don’t know much about ATP and IMP, except my descriptions for them in the article. But I realized that the words came on the article before my descriptions of them. That was probably what confused you. I changed my writing to avoid the confusion. Thank you very much once again for pointing it out.

  2. Ben D
    Ben D07-17-2013

    Ths is a very good summary of the benefits of ikejime. We have developed a website with information on brain location of a range of Indo Pacific fish species at http://www.ikijime.com. I would like to link to your webpage as it complements the information we have on our site. Please let me know if this is OK.

    • Totos

      Hi Ben.
      Thank you for kindly asking for a link from your website. Glad you find our site helpful. Go ahead and link, and we’ll have a link to yours.

  3. Dimitri

    Excellent article. We immediately close the fish, but the trick with the spinal cord is quite new to us…
    Any ready made instruments to make life easier, instead of making our own?
    How do you practice ikejime to a bft tuna which is 1.40m long?

  4. Totos

    Hi Dimitri.
    They are selling Ike-Jime wire around JPY1,000. They are made of shape memory alloy so that it’s always straight when uncoiled.
    But it really doesn’t have to be a specific wire. I used to use a stainless heavy gauge wire which is meant to make rigs, about 1mm diameter, you can buy at any fishing store.

    For longer fish than your wire, go into the spinal cord from the head once, and go again from the tail.
    Doing both video 1 & video 2 on Ike-JIme Part 1.

  5. Wei

    Quote” Ike jime closing. I always do it like this. Sandwich the fish with the soles of my shoes, and put in the wire along the spine. I see the target line more clearly this way. Then it was laid in a cooler box, in the plastic bag on the ice for a whole day on the boat. When we were back in the evening, the fish body was not stiff yet, soft like live. Then I scaled, gutted, and filleted that night. Wraped it with a paper towel which sucks out the liquid but stays dry on the contact side, no plastic wrap, and put it in the fridge.

    Hi Totos

    Your information on Ike Jime is very interesting and I would like to follow your practice to try this method. You mentioned above that the fish is wrapped in paper towel and put in fridge. I will appreciatevif you could advice by putting in the fridge, what temperature is it stored? It is not in the freezer, I guess.

    • Totos

      Hi Wei.
      Thank you for your comment.
      The study of Hokkaido University shows that it’s better to store around 10C for the first day and around 5C for the following days. So just put it in a normal fridge temperature which is about 4C unless the door gets opened frequently.
      One thing to concern is the drip. When the meat is soaked in the drip, it goes bad no matter how cool it’s kept. That’s what the paper towel is for and you want to change it once a day.
      Enjoy your catch!

      • Yani

        Hi Totos
        I read somewhere that the best storage temperature was about 10-20 Celsius. I am not doubting you or something Im just confused on what the real storage temperature is.
        Thank You,

        • Totos

          Hi Yani.
          The study of a Japanese university shows that 10C is best for 6 hours after ike-jime, and 5C after that. Because when it’s too close to 0C, the meat tightens, in spite of that fact you did Ike Jime in order to keep the fish NOT tightened. But it’s never over 10C.

          • Yani

            Thank You!!!!

  6. Chris Wong
    Chris Wong07-16-2014

    Thankyou for this most informative piece. Although I normally Iki my fish, I also like to cut the throat to drain off the blood. I will have to change how I chill down my fish in future. I always wonder how the Japanese are able to produce glassy translucent fillets of fish that look so fresh with high quality.

    • Totos

      Hi Chris.
      I know. It looks like a magic if you don’t know. But there’s always tricks, maybe I should say, procedures. If you follow these procedures of Ike Jime, you will have this beautiful fillet!

  7. Yani

    Hi Totos,
    This guide you made on ike jime was so helpful. I just wanted to ask when do you start to put the fish in the freezer, after a week ?

    • Totos

      Hi Yani.
      Thank you for your compliment. I’m glad the info helped you.
      Yes, most of the non-oily white meat fish can last 5 days of aging after Ike-Jime. But it’s actually the last option to put into freezer after aging. The defrost process will ruin the meat.

      It’s actually the first day decision whether or not you will put the fish into freezer. You want to make this decision within 24 hours after Ike-Jime.
      Freezing is the last option anyway. I would try ajillo, garlic and red pepper oil cooking, or cold smoke which makes it last for good 2 weeks in the fridge. When you sun-dry, the freezing will not change the quality.

  8. Cal

    How about lobsters?

    • Totos

      I don’t know much about crustacean. But it seems that their enzyme starts breaking down the cells so much faster than fish when they are dead. Ike Jime slows down the process but it doesn’t stop it. They are better left stored alive. They store them alive in sawdust for a week. Or freeze it. Freezing doesn’t ruin the meat as much as the fish.

  9. Jordy

    Great site! Your posts are very informative and very helpful. Thank you so much for this!

    • Totos

      Sure Jordy. Thank you for your compliment. Let me know if you have any questions.

  10. Mauro

    Totos, greetings from Argentina. I am no fisherman but i am a cook. I read about Yoshinori Ishii in Umu an about the “fish and chips revolution” and looking more into Ike Jime i found your article. Thank you very much for such a clear explanation.
    Best regards

    • Totos

      Hi Mauro.
      Glad to be of help to you.
      I heard about Ishii-san of UMU. He had trouble finding sashimi quality fish in London. He found the local fishermen spend couples of days at sea once they go out. No wonder fish in the market is not fresh and damaged. They keep fish alive in the hold while at sea, but every sushi chefs know now that the stress in the tank chews out the fish.
      He found one area where fishermen fish with a line on small boats and come back daily. He taught them Ike-Jime and had a deal with them for his restaurant.

  11. Dan

    Hi Totos – I hope you’re well. Sorry I haven’t been in touch with you for a very long time, I’ve been very busy lately.
    Just wanted to say Part 2 of this iki-jime piece is excellent, thank you for posting.

    • Totos

      Thank you Dan.
      Great to hear from you. Hope you are not too busy to go fishing from time to time!

  12. Samuel Chieng
    Samuel Chieng06-13-2016

    Hi Totos,

    I found your information on closing fish very helpful. My question is, over in our waters sometimes we catch a lot of fish and the fridge will not have enough space to store. We always put in big freezer to store for maybe few weeks. Will the fish meat drop in quality after being defrosted even after the proper steps taken to close it? Are there any other steps beside cold smoking to make the fish last longer than few days?


    • Totos

      Hi Sam.
      Yes. Unfortunately, fish loses so much quality by freezing. We’ve been trying to figure out all the methods to keep the fish quality without freezing. Ike-Jime doesn’t make any difference if you freeze it.
      The best you can do is semi-dry. Semi-dry will not lose much by freezing because the moisture is what damages the fish by crystalizing in freezing process.
      You should just get a big cooler box. Here’s what I do.

  13. agus

    Hi Toto,

    Thanks for the information in this website. I have a question regarding fish ageing.

    In my local my fish market, I always see big fishes like salmon and halibut that are sitting on top of crushed ice, cleaned (no guts and blood), firm meat but not stiff. Does this mean that it is already in phase 3, the maturing stage? Should these fish need more maturing in the fridge or should it be eaten the day it was bought to maximize taste?

    • agus

      I also want to add that there is no sign of the fish being closed with ike jime method, but i assume that it was bled as it is quite a common practice in commercial fisheries. The fish i am sure would have gone through the mortis rigor stage as commercial fisheries usually stay out at sea for a few days. I asked the seller and he said that the fish has never been frozen and was caught recently, though he is not sure when exactly.

      • Totos

        Exactly. Usually you can’t find out how the fish is closed in the commercial fishing.
        I doubt that bleeding is even common. As far as I know, it’s not so common even in Japan. Bleeding fish takes time and it can disturb the rhythm of their work on the busy boat. And bleeding is only possible by the fishermen who fish one by one with hooks.
        When they fish with nets, they don’t bleed all the fish which are caught at once. Sometimes they leave baits on buoys and collect fish the next morning. Fish are all dead when they catch.
        All the fish you find on the ice in the market have passed rigor mortis. You just don’t know how long it has been since closed. You shouldn’t risk it. Only way to find out is to taste and judge for yourself.

    • Totos

      Hi Agus.
      Yes, I think these fish on ice has already passed rigor mortis stage.
      But please note that aging increases the taste, at the same time, it loses the texture. So it depends on the fish, and it depends on your preference. Personally, I think the beauty of halibut is in the texture. I find the sashimi at its best after only a day, or only sometime 2 days, after closing. If it passed that, it becomes,,, how can I say, “ordinary”. Salmon can be aged longer, depending on how to cook it.
      Sometimes it’s hard to find out, in the fish market, when it was closed and how it’s closed. You just need to taste it to know how much it’s aged.

  14. Daz

    Hi Totos, hope you are well. Just a question in regards to the use of wire and the term Ikejime. A lot of people in Australia, including myself, close the fish with a spike into the brain and bleed the fish but they don’t use the wire into the spine.
    Am I correct in saying the proper meaning of the term would include the wiring of the spine?
    I feel as though we are only completing half of the procedure if we don’t used the wire.
    Is the wiring very important?
    Thanks for all of your helpful info,
    Regards Daz

    • Totos

      Hi Daz. Good to hear from you.
      Wiring is the latest addition to Ike-Jime. Wiring is to destroy spinal cord. What that does is explained in this page. It slows down Rigor Mortis and save Umami components in the cells, which you will lose otherwise. It makes a big difference if you age the fish for 3 days or more. If you eat the fish on the day of the catch, it doesn’t make any difference.
      You don’t have to think. Try and see for yourself. I can put the wire in your next order. It’s only JPY1740.

      • Daz

        Thank you my friend.

  15. FenixRyzng

    Thank you so much for this article. It was wonderful and now I know how to properly dispatch my fish.

    • Totos

      Hi Fenix.
      Thank you for your comment.
      Good luck and enjoy your catch.

  16. Chris.

    Master Totos thank you very much for all the information about this topic and the slow pitch.

    • Totos

      Hi Chris.
      I’m glad my website helped you enjoy fishing and eating!
      Good life!

  17. Lian


    Thanks for sharing the above information.
    Could you please provide the tittle or link to the study mentioned please ‘Research project by Hokkaido University in 2012’.

    Kind regards,

  18. Daniel

    Hi Toto,
    Does ike jime have the same effect in squids? Are the taste and meat consistency better? Is also the aging period longer?

    • Totos

      Squids feel to me like they are from out of space. They are so different from fish in many ways. They are not vertebra.
      Many people in Japan say Ike-Jime would not make any difference with squids.
      In many cases, you freeze them to protect from parasites, too.

      However, many anglers does ike-jime with big-fin reef squids. I do too. It’s more like compassion, I think. If you kill it, don’t let it suffer. Just close it immediately.

      • Daniel

        Thank you Totos

        Isnt there any ike jime studies with squids in Japan?

        • Daniel

          I read some studies that say that squids, like actupus, are very inteligente animals, and they feel pain (proved). But nothing about squid ike-jime studies …

  19. Daniel

    Hi Totos
    Do you have some experience, know, or have some idea when the Bluefish should be eaten after the fish has been properly closed and stored, from day 1 to day 5? Is its time similar to Tuna, Trevally, Amberjack, Snapper, Grouper? I would guess its time is more similar to Trevally…
    Regards, Daniel

    • Totos

      Bluefin? Only fish I can think of is bluefin tuna. Is there any other fish called bluefin??
      Bluefin tuna is big and oily (with unsaturated fats). That makes aging very difficult with this fish. Professionals will age this big fish for days and weeks. But it needs to be in the specific controlled temperature, otherwise the unsaturated fats are quick to be oxidized. I would not take much chance. Just age for a couple of days. A couple days is not even aging for a big tuna. Just resting until all the tension from the killing is loosened. Tight pack and absorb drips in the coolest place in the fridge. It does not mean that it will go rotten after a couple of days. Oxidation makes an unpleasant taste and smell. If you see or smell the oxidation, you should slice off the surface to throw.

      • Daniel

        Hi Totos

        It is not a bluefin tuna, it is another fish called blue fish. It is very commun all arround the world.


  20. Daniel

    Hi Totos

    I am not enable (or dont know how) to add a picture. But follows a link of a bluefish (with a picture of it):


    Regards, Daniel

    • Totos

      Hi Daniel.
      Thank you for correcting me. I see it. OK, we don’t have this fish in the northwest Pacific around Japan.
      I don’t know. Fish are really all different. You just have to figure it out with your own experiments.
      But my point stays the same. It’s the oxidation that you should watch for. Not just Ikejime, you should do tight seal, with drip absorption, and keep it as cool as possible.
      Normal fridge keeps about 4C or 5C degrees. And it rises every time you open it. When sushi chefs age Tuna for days and weeks, they keep it at 2C or 3C in the professional fridge to avoid oxidation and smelling. My friend sushi chef told me that 1C different can ruin the fish.
      Anyway, if this fish is close to AJ and yellowtail, it’s easier. But if it’s close to tuna family, it’s very easy to start smelling.
      You just have to find out by yourself. Good luck!

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