Welcome to FISH FOOD TIMES
Jul. 2025 issue No.259
Roughscale sole
In addition to mimicry ability, it also has defensive ability.
I got 1.4kg of roughscale sole that had been immediately killed.The image below shows the roughscale sole after I purchased it and without washing it or anything, just placing it on the cutting board. The top side (the side with eyes) is covered with countless large and small pebble-like protrusions, and the rugged surface looks almost like armor. The name "roughscale sole" is apparently derived from the fact that the top surface is rough like shark skin, but it is not just rough at all; I think "bumpy" would be a more appropriate word.
Looking at the pebble-like protrusions on the upper surface of the roughscale sole, this surface looks just like sand, and it is imagined that this shape gives the fish a superior mimicry ability than other flatfish.
The mimicry ability is a phenomenon in which cells called chromatophores in the skin of flatfish, including the roughscale sole, change the color of their bodies by expanding or contracting the pigments in their skin based on the brightness and color information of the surroundings captured by their eyes. The roughscale sole changes its surface color to match the color of the sand or gravel on the seabed, so when it lies still on the seabed, it looks like it is part of the sand.
The roughscale sole not only has mimicry ability, but the armor-like skin on its top surface is very tough, so even if it is attacked by a predator, this sturdy skin must provide a defense far superior to that of other flatfish.
Furthermore, as you can see by looking closely at the image above, there is a much larger amount of cloudy white slime on the surface of the fish's body than in other fish. Slime is very slippery, so if there is a lot of it, it makes it harder for predators to catch it, and it acts like a barrier to protect the body from external enemies, so in that sense, the roughscale sole, which has an extremely large amount of slime, can be said to have excellent defensive capabilities.
On the other hand, if you look at the bottom surface (side without eyes) in the image above, you will see that it does not have any bumpy protrusions like the top surface, and has a relatively soft skin that feels squishy and elastic when pressed with your fingers, with skin that has a completely opposite texture to the top surface.
Seeing the extreme difference between the top and bottom surfaces of roughscale sole, I felt that the cooking of roughscale sole should take a completely different direction between the top and bottom.
Fish cutting work of roughscale sole
The direction of the cuisine was to commercialize the top surface as sashimi and sushi, and the bottom surface as fillets. First, fillet a fish into two pieces on the top surface, then separate them.
| Roughscale sole top surface fillet a fish into two pieces work process | |
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| 1，Use a scrubbing brush to wash away the slime on the top surface, which has countless protrusions. There is a lot of slime, so it takes time to remove it and is not easy. | 6，Make an incision near the base of the tail fin, then use a reverse-handed knife to cut along the edge of the fin toward the head. |
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| 2，There isn't much slime on the bottom surface so it doesn't take long at all. | 7，From the cut near the fin, cut open the abdomen and proceed above the centralbone. |
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| 3，A roughscale sole after the slime has been washed away and the water has been wiped off. | 8，Next, cut over the central bone towards the backbone, avoiding the fish eggs. |
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| 4，Since an immediately killing incision had been made, I cut that area further towards the abdomen. | 9，Cut past the backbone and beyond, detaching the top surface. |
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| 5，Separate the section between the head and the body. | 10，The state with the top surface separated. |
The skin on the top surface was tough, so I used a reverse-handed knife to make a cut along the entire fin edge, but when I tried to use a reverse-handed knife on the bottom surface, the skin was squishy and elastic, so there was no resistance from the blade, which made it actually more difficult. For this reason, almost at the very beginning, I switched from a reverse-handed knife to an overhand grip knife, made a cut along the edge of the fin, and then began the process of one side filling.
| One side filling of the bottom surface of the roughscale sole | |
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| 1，Using an overhand grip knife, make a cut near the fin and then begin filleting the fish. | 3，Cut beyond the backbone and beyond, detaching the bottom surface. |
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| 2，Cut above the centralbone toward the backbone. | 4，The state of the central bone remaining after filleting a fish into three pieces using the one side filleting method. |
The top surface is used for sashimi and sushi.
The skin of the top surface is hard and bumpy, so it is a little difficult to cut it with a deba knife. For this reason, for example, there is a method to peel it off by pulling it off by hand without using a knife, but I decided to avoid using that method.
Of course, when it comes to filefish, I naturally pull the skin off of the fish by hand, but I actually had a bitter experience of trying it the same way with a real bonito in the past and being laughed at. I wonder how many years ago that was...maybe 15 to 20 years ago...
I saw a method of peeling off the skin of bonito by hand at a certain place, and I thought it was interesting, so I tried it at another place. However, the people who saw it showed an atmosphere of ridicule along with the reaction of surprise. This is because, although the skin could be removed, a thin skin remained in a strange, half-finished shape, making it difficult to develop the dish afterwards.
Since then, I have decided to never pull the skin off of a bonito by hand, and I regret it. Therefore, I am concerned that if I pull the skin off of a roughscale sole by hand, a thin skin similar to that of a bonito will remain.
I decided to peel the top surface of the roughscale sole using the outer pulling method, which certainly created a lot of resistance to the edge of the yanagiba blade and required a fair amount of force, but I was able to peel it without any problems. However, after removing the skin, there were a few tiny speck-like spots remaining on the surface of the fish meat. This is a phenomenon that those who understand will understand.For example, when someone who is good at cutting corners is tasked with filleting and skinning a large number of red sea bream, they may be seen to skip removing the scales, fillet the fish into three pieces, and then skin it with the scales still on. These are small spots that often occur when skinning is done in this way.
After peeling the roughscale sole, there were some tiny spots remaining, but I removed them immediately with the tip of a yanagi blade, so there are no pictures of them. Since I peeled the roughscale sole without removing the scales (there are no scales in the first place), it is not surprising that some such spots existed.
I decided to make the back body into sashimi and the belly body into sushi, and the process of skinning the top surface and creating the saku shape was as follows:
| The process of skinning the roughscale sole and creating the saku shape | |
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| 1，Half of the top surface after filling a fish into three pieces. | 5，After removing both floor edges and the belly bone, the skin was removed using the outside skinning technique. |
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| 2，Before removing the collar of the fish and the belly bone, cut off the flounder edge on the belly body side. This is to ensure a long flounder edge. | 6，Remove the skin from the flounder edge. |
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| 3，Cut off the floor edge on the back body side. | 7，Separate the back body and belly body. |
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| 4，Cut off the collar of the fish and remove the belly bone. | 8，Remove any remaining chiai bones on the belly body side. |
In the above process, the flounder edge is separated before removing the collar of fish and the belly bone. This is to ensure that the flounder edge is as large and as long as possible. This is not only for the top surface, but also for the bottom surface, when cutting the fillet, the flounder edge must be removed first before cutting the fillet. Since I had the good fortune of obtaining a fresh roughscale sole, I wanted to use it as valuable sashimi and sushi, rather than cutting the flounder edge into fillets and cooking it with heat.
| Roughscale sole nigiri sushi using flounder edge | |
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| 1，Cut the belly body on the top surface using the sogitsukuri technique while in a left position. | 4，Line up the two flounder edges and trim the left edge. |
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| 2，Make 10 pieces of sushi material using only the belly body. | 5，Trim the right ends of both flounder edges to the same length. |
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| 3，Peel the two flounder edges. | 6，Cut the two flounder edges in half to make 4 pieces of sushi material. |
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| Four flounder edge pieces of roughscale sole nigiri sushi arranged on the second tier from the top | |
Next is sashimi using belly body. Use flounder edge for sashimi as well to make it more attractive.
| Roughscale sole sashimi using flounder edge | |
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| 1，Turn to your right and begin by cutting the back body of the top surface in the usutsukuri way. | 5，Place the usutsukuri sashimi on the top right of the tray, starting from the right. |
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| 2，On the top left of the tray, arrange the usutsukuri sashimi in a semicircle from right to left. | 6，Cut the flounder edge into sogitsukuri sashimi. |
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| 3，Thinly slice the cucumber. | 7，Place the flounder edges of sogitsukuri sashimi on top of the semicircular cucumber slices. |
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| 4，Lay the sliced cucumber in a semicircular shape. | 8，Place the usutsukuri sashimi on the bottom right of the tray and the flounder edge sogitsukuri sashimi on the bottom left. |
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| Sashimi made from the back body of the top surface of a roughscale sole and its flounder edge | |
The sushi and sashimi using the top surface of the roughscale sole is now complete. Next is the bottom surface. In contrast to the top surface, the bottom surface has soft skin and squishy, elastic flesh, and you can see just by looking at it that there is plenty of fat under the skin. I'm sure the bottom surface of roughscale sole would be delicious as sushi or sashimi, but it's also a fish that makes me want to try cooking it.
The first image that comes to mind when thinking of cooking this is Western-style dishes such as sautes and meunière. This time, we used fillets of roughscale sole that had plenty of fat, so we decided to make a dish with poilet to bring out the flavor of the ingredients.
| Process of cooking a dish with poilet using the bottom surface of a roughscale sole | |
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| 1，Cut off the collar of fish from the bottom surface. | 4，The head side of a fillet that has been cut horizontally in half. |
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| 2，Separate the flounder edge for sashimi and sushi. | 5，The tail side of a fillet that has been cut horizontally in half. |
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| 3，Cut off the flounder edge on the back body side. | 6，Season the fillets with salt and pepper, coat them in flour, and then fry them in a frying pan with olive oil. |
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| A dish of roughscale sole with poilet is ready. | |
Roughscale sole rating
Roughscale sole has so much slime that the surface of the body looks white, and the top surface is bumpy with countless hard protrusions, making it look unsightly, so it seems that it was poorly handled in its production areas, such as Hokkaido in the past.
The image below was taken at a local fish market in Hokkaido. In this photo, fish that are not expected to fetch a high price due to their species, size, freshness, etc. are thrown together carelessly into a large metal container of ton-class. These fish are probably destined to be processed into meal and turned into pet food, but the roughscale sole must have been treated the same way in the past. This is because roughscale sole is slimy and fatty, making it synonymous with cheap fish, and it is also poorly handled in its place of origin, making it one of the fish that does not fetch a good price.
However, as shown in the image below (taken by the author at Akkeshi Fish Market on November 3, 2017), in recent years, efforts have been made to increase the value of roughscale soles, such as by carefully washing off the slime before they are listed on the fish market, and as a result, the price seems to be gradually increasing. Furthermore, due to consumers' increasing preference for fat, roughscale sole that has been immediately killed has now become classified as a luxury fish.
The roughscale sole I handled this time was caught in Hokkaido and was immediately killed, and was extremely fresh. Although roughscale sole is a fish that is caught in large quantities in Hokkaido and Tohoku, the one I bought in Fukuoka, where I live, was very fresh, so if you are willing, you should be able to get fresh roughscale sole anywhere in the country.
If roughscale sole is not yet a familiar fish in the fish section of your fish store, I hope that you will take this opportunity, having read this month's issue to the end, to try handling roughscale sole.
An opinion and the communication are to iinfo@fish food times
Date of updating 1 Jul. 2025
