You don't need to memorize every way to fillet a fish. 90% of fish can be filleted using the '4 shapes' taught by professionals [with table and explanation]
Have you ever encountered a delicious-looking fish you've never seen before at a supermarket seafood section or a fishing spot?
“I want to try eating it, but I don't know how to fillet it...”
It's not uncommon for people to have that experience, which is why they always end up choosing pre-cut fillets of horse mackerel or salmon. If you search on YouTube, you can find step-by-step videos, but there are countless types of fish. It's a hassle to have to search every time you cook, thinking, 'This video for horse mackerel,' 'This video for flatfish,' 'This one for squid,' isn't it?
“Do professional chefs memorize how to fillet every single fish?”
You might think so, but that's actually not the case. We professionals don't “rote memorize” how to fillet fish. We look at the “shape (body type)” of the fish and judge on the spot which filleting method is appropriate.
Once you know this 'standard for judgment,' even if you see a fish for the first time, your hands will intuitively know, 'If it's this shape, I should fillet it like this.'
In this article, we will reveal the “common rules” for filleting fish that the Shokunin Daigaku (Culinary Institute) teaches to train sushi chefs in a short period of three months.
We won't talk about difficult technical terms or rely on a chef's intuition. If you understand the structure of a fish's bones and the 'logic' behind making food delicious, cooking fish becomes much more free and enjoyable.
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Conclusion: How to fillet a fish is determined by its 'body type' [Classification Matrix Table]
First, let me start with the most important conclusion.
The way to fillet a fish is determined by how that fish swam in the ocean, in other words, its “body type (body plan)” . By keeping the following four patterns in mind, you will be able to handle almost any fish.
Correspondence table for fish by body type and filleting method
What do you think? Instead of memorizing by 'fish name,' classify by 'shape.' This is the map inside a professional's head.
From the next chapter, we will explain in detail why each filleting method is used for that shape, along with tips to avoid failure.
The Definitive Edition! A complete guide to 'types of filleting' from basics to special techniques
From here on, based on the classification above, we will delve deeper into the specific types of filleting and the reasons why those techniques are chosen.
1. [Basic] Three-piece fillet
This is the most popular technique and the absolute basic of filleting fish.
What kind of fish is it used for?
Most of the 'swimming fish' you see every day, such as horse mackerel, sea bream, mackerel, yellowtail, and tuna, are filleted this way.
What is the structure?
It is called 'sanmai-oroshi' (three-piece fillet) because the fish body is divided into three parts: the left fillet, the right fillet, and the center bone (with the head).
Professional perspective: Why three pieces?
These fish have symmetrical muscles on either side of the spine. By inserting the knife along the spine, you can remove the meat with the least amount of waste.
The important thing is to utilize the 'weight' of the knife. Especially with large fish like red sea bream or yellowtail, the center bone and head bones are very hard. This is where a 'deba knife' comes in handy. A deba knife has thickness and weight, and by using that weight to 'drop' the knife and cut through the bone, even someone without much strength can cut through hard bones.
Also, to ensure no meat is left on the bone, professionals rely not only on sight but also on 'sound and feel'. By feeling the 'crunchy' sensation of the knife tip hitting the bone as you move the blade, you can cut right along the edge.
2. [Efficiency-focused] Daimyo-oroshi
This is a variation of the three-piece fillet.
What fish is it used for?
Small fish like Japanese whiting, small horse mackerel, and sardines, or long, thin fish like cutlassfish and saury.
What is the technique?
Instead of carefully inserting the knife in the order of 'belly, back, belly, back' like in a three-piece fillet, you remove the head and then run the knife along the center bone in one go to separate the meat.
Pros and cons
Pros: It is overwhelmingly fast because there are fewer steps. Also, since you touch the fish fewer times, you can prevent the freshness from dropping due to the heat of your hands.
Cons: A lot of meat is left on the center bone.
It is said that this name comes from the fact that it is a way of eating that 'leaves meat luxuriously,' like the feudal lords (daimyo) of the past. However, in modern professional kitchens, the remaining bones are served as 'bone crackers' (hone-senbei) to make sure they are used deliciously without waste.
3. [High difficulty] Five-piece fillet
This is a filleting method exclusively for 'flat fish' like flounder and sole. You might wonder, 'Isn't a three-piece fillet okay?' but there is a clear reason for this.
What fish is it used for?
Flounder, sole.
What is the structure?
It is called 'five-piece filleting' because it divides the fish into five parts: the top flesh into 'back and belly' (2 pieces), the bottom flesh into 'back and belly' (2 pieces), and the central bone (1 piece).
Pro perspective: Why five pieces?
Flounder and sole have flattened bodies to cling to the seabed, but in reality, the spine is not in the middle of the body's thickness, but rather in the 'middle of the width'. Furthermore, the 'engawa' (fin muscle) used to move the fins is well-developed.
If you try to force this into a three-piece fillet, the precious engawa will remain on the bone, or the flesh will fall apart. In five-piece filleting, you make cuts along the spine in the center of the body and move the knife to 'peel' (scrape) the flesh outward. By doing this, you can match the complex shape of the bones and remove the engawa cleanly.For a sushi chef, whether or not they can beautifully fillet a flounder into five pieces is also a milestone of technical achievement.
For a sushi chef, whether or not they can beautifully fillet a flounder into five pieces is also a milestone of technical achievement.
4. [Regionality] Back-opening/Belly-opening (Kanto style/Kansai style)
A technique used for 'long fish' like eel and conger eel. Here, let's touch upon not just the difference in procedure, but the interesting culture and logic of the 'difference between Kanto and Kansai'.
What is the technique?
Back-opening (Kanto): Insert the knife from the back and open it while the belly side remains connected.
Belly-opening (Kansai): Insert the knife from the belly and open it while the back side remains connected.
Why is it different by region? (Common myths and the truth)
A common theory is that 'in Edo (Kanto), where there were many samurai, they avoided back-opening to prevent the association with seppuku, while in Osaka (Kansai), where there were many merchants, they used belly-opening to symbolize opening up and speaking honestly.' However, in the culinary world, there is a more rational 'culinary scientific reason'.
Reason for Kanto (back-opening): Kanto-style eel dishes include a 'steaming' step before grilling. Steaming makes the flesh very soft, so if you were to use belly-opening (where the thin belly side is at the edge) and skewer it, the flesh would tear and fall off the skewer during steaming. By using back-opening, you can pass the skewer through the thick back meat, making it less likely to fall apart when steamed.
Reason for Kansai (belly-opening): Kansai style mainly uses 'jiyaki' (direct grilling) without steaming. If grilled for a long time, the skin shrinks and the flesh tends to curl, but belly-opening is more resistant to shrinking when grilled and makes it easier to maintain a flat shape. It is also suitable for grilling aromatically while letting the belly fat drip off appropriately.
In other words, the difference in filleting methods is the result of rational evolution to match the subsequent 'difference in heating methods'.
5. [Special] Hand-opening
A filleting method that does not use a knife.
What kind of fish is it used for?
Sardine (Iwashi).
Professional Perspective: Why use your hands?
The Japanese kanji for sardine is written with the character for 'weak' next to 'fish,' reflecting how incredibly soft and delicate the flesh is. Furthermore, sardine fat has a low melting point, meaning it can easily melt from human body heat or the friction heat of a knife, and it is prone to oxidation (degradation) when it reacts with the metal of a knife.
By using your fingers to gently separate the bones from the flesh—a technique called 'hand-opening'—you can avoid damaging the muscle fibers and prevent metallic odors from transferring, thereby preserving the sardine's natural umami. Small bones also tend to come away with the main bone, making this a two-birds-one-stone technique.
6. [Special] Sukibiki (Skin-Slicing)
A special technique for removing scales.
Which fish is it used for?
Fish with fine scales and thin skin, such as tilefish, flounder, and grouper.
What kind of technique is it?
Instead of using a standard scaler (a scraping tool), you lay a sashimi knife flat and cut away only the scales on the surface of the skin as if you were 'thinly slicing' them off.
Professional Perspective: Why use sukibiki?
Because these fish have soft flesh, trying to remove scales with force would crush the meat. 'Sukibiki,' which removes only the surface like a surgical procedure, is an advanced technique that results in zero damage to the flesh while also preventing scales from scattering around the kitchen.
7. [Special] Tsutsugiri (Cross-Section Cutting)
A technique for cutting fish without opening them up.
Which fish is it used for?
When making simmered dishes with Pacific saury, mackerel, sardines, etc.
Professional Perspective: Why use tsutsugiri?
Simmered fish can easily fall apart when cooked for a long time. By cutting them into cross-sections, the skin and backbone maintain a cylindrical structure (arch structure), which makes the fish less likely to fall apart. Additionally, because good stock is released from the cross-section of the bone, it has the benefit of increasing the richness of the broth.
[True Story] Craftsmen who mastered the 'correct method for each fish species' in 3 months
'I don't have the confidence to memorize so many types and theories...'
You might have thought that. In the traditional world of apprenticeship, it was taken for granted that you would 'watch and steal' techniques, spending years learning them with your body.
However, at Inshokujin University, these techniques are mastered in just three months through a repetition of 'theory' and 'practice' . Here, we introduce the voices of graduates who started with no experience and completely mastered the filleting methods for each type of fish.
Practicing '5-piece filleting of flounder' and 'opening conger eel' with confidence
Looking back on his intensive three months at Inshokujin University, Mr. Shiba cites '5-piece filleting of flounder' and 'opening conger eel (belly and back)' as the classes that left the biggest impression on him.
These are high-difficulty techniques that are rarely performed in home cooking. However, Mr. Shiba mastered them not just as knowledge, but as skills at a level where he can serve them to customers in a professional setting.
Why is it possible to become so capable in such a short period? It is because Inshokujin University thoroughly teaches the 'logic' behind why a certain filleting method is used. If you understand the logic, you understand the cause of failure. If you understand the cause, you can make corrections. By running this cycle at high speed, it becomes possible to compress 10 years of training into three months.
☞Click here for the full interview with Koshin Shiba
Learning the optimal solution for 'this fish' rather than 'because it's a fish'
The biggest takeaway Mr. Matsushita gained at Inshokujin University was an increased 'resolution' regarding fish.
He was taught, 'This is good for flounder. This is good for sea bream,' rather than 'It's a fish, so do it this way,' and he continues to practice this today.
Speaking in this way, Mr. Matsushita acquired the skill to change his filleting and preparation methods according to the individual differences and characteristics of each fish, rather than grouping them all together.
Knowing the 'types of filleting' alone does not make you a professional. Being able to look at the state of the fish in front of you and apply techniques, such as 'Today it's fatty, so I'll leave the skin on and blanch it (yushimo),' is the image of a 'craftsman who can work in the field' that Inshokujin University aims for.
☞Click here for the full interview with Ryo Matsushita
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Frequently Asked Questions (FAQ) about fish filleting
Here, we have summarized points that people who are about to try fish filleting for the first time often wonder about.
Q. What is the most difficult type of fish to fillet?
A. Generally considered difficult are 'conger pike' which requires bone cutting, and 'pufferfish' which requires the removal of toxic parts. These require special techniques and qualifications (in the case of pufferfish). Also, among familiar fish, the 5-piece filleting of 'flounder' is high in difficulty, as it is hard to cleanly leave the fin muscle (engawa) if you are not used to it. However, if you understand the bone structure, you will definitely be able to do it.
Q. What fish and filleting method should a beginner start with?
A. For beginners, I recommend filleting horse mackerel (aji) into three pieces. Horse mackerel are a manageable size, their bones aren't too hard, and they are inexpensive at the supermarket. Also, because their structure is the 'gold standard' of basics, if you can fillet a horse mackerel, you can apply those skills to many other fish like sea bream or mackerel. Start by getting a feel for 'the knife gliding over the bones' with a horse mackerel.
Q. Should I change my knife depending on the filleting method?
A. Yes, changing your knife will help you improve faster. Basically, for rough tasks like cutting through bones or removing the head, use a heavy, thick deba knife. Then, for delicate tasks like slicing the fillets into sashimi, use a long, sharp yanagiba knife. Understanding the roles of your tools is the first step toward eating fish deliciously without damaging its cells.
Summary: Skill is built not by 'time' but by 'density'
At first glance, fish filleting methods may seem complex and numerous, making them seem difficult to memorize. However, as introduced here, there is always a 'reason' behind them.
Fish that swim around are filleted into three pieces.
Flat fish from the seabed are filleted into five pieces.
Long fish are opened up.
Weak fish are opened by hand.
Once you understand these simple rules, you will never stand frozen in front of a fishmonger again. You will be able to confidently choose, 'This fish is spindle-shaped, so it's a three-piece fillet'.
At Inshokujin University, we teach these 'culinary principles' one by one, carefully and practically. Instead of 'learning by watching,' we explain 'why we do it that way' in words and practice it with our hands. That accumulation of high-density time is the secret that turns beginners into professional sushi chefs in just three months.
Why don't you learn to fillet fish freely and enrich your dining table? First, request our free brochure to see the full scope of our curriculum.
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