Aburasokomutsu Sushi

aburasokomutsu sushi

What is Aburasokomutsu アブラソコムツ ?

Aburasokomutsu is the Japanese name for the escolar, which is supposedly called “butterfish” or “white tuna” in the trade. Contrary to this name, the escolar does not belong to the butterfish family, but belongs to the snake mackerels. Unlike in Japan, you can often find aburasokomutsu in the display (neta-bako, ネタ箱) of western sushi bars and restaurants.

The name “butterfish” or “white tuna” originates from a purely commercial motivation and should sound more appealing to the consumer. However, its full-bodied, very fatty and slightly sweet taste, reminiscent of butter, cannot be denied.

Escolar as Sushi or Sashimi

There is hardly any other fish that is better suited to the false name “butterfish” or “white toro” than the escolar. The shiny, matte white meat is firm, very tender, full-bodied and accompanied by aromas that have a strikingly strong taste of butter. Compared to tuna, the meat is slightly more sour and less fresh in taste.

When preparing as Sushi or Sashimi, one should avoid the excessive use of soy sauce or wasabi, a thin glaze is more sufficient. Alternatively, the buttery flavors harmonize very well with a touch of citrus (e.g. yuzu).

As the flesh of the escolar contains wax-like lipids, one should refrain from eating larger quantities, as these cause digestive problems (keriorrhea).

Food Fraud

Investigations by the marine protection organization Oceana, showed that escolar was wrongly labeled both in restaurants and at fish markets. The Oceana study concluded that from 2010 to 2013, approximately 84 percent of the 114 tuna samples identified as "white tuna" were actually escolar (Warner et al., 2013).

Wrong marking, whether due to ignorance or deception, is a serious problem especially with the escolar. Escolar can cause digestive disorders, especially diarrhea (keriorrhea), when consumed due to the wax-like lipids contained in the meat. These lipids are heat-resistant and do not disintegrate when heated. In the absence of dose-response studies in the medical literature, even doses of 95 grams are classified as laxative.

Escolar in Japan

In June 1998, food poisoning occurred in Tokyo as a result of eating cooked fish on the lunch menu of a restaurant. Twenty-one out of forty people were poisoned. Their main symptoms were skin irritation, headaches and palpitations. Consequently, it was confirmed that the fish responsible for the poisoning was aburasokomutsu (Kan et al., 2000).

The Japanese Ministry of Health, Labor and Welfare (厚生労働省) lists aburasokomutsu as a risk source for natural poisoning by abnormal lipids and has been banned for consumption since 1981.

Characteristics & Ecology

The escolar prefers temperate and tropical waters, especially on continental slopes, around the world. They are usually found individually or in pairs, usually at a depth of 200-1100 m (656-3609 ft). Adult specimens can reach a size of over 2 m (6.6 ft) and weigh up to 45 kg (99 lb). Juveniles in particular, but also larger individuals migrate vertically to the surface at night to feed on fish, crustaceans and especially squid.


According to the Food and Agriculture Organization of the United Nations (FAO), the three largest fishing nations in 2018 were Ecuador, Spain and Portugal. Escolar is rarely targeted and is more often part of the by-catch of other species (Levesque, 2010).

Diagram showing the progress of the catch of escolar.
Because escolar is rarely targeted, the quantities caught are subject to wide fluctuations.


© KHON2 News. Beware sushi menus that offer 'white tuna' or 'white maguro'. 2015-05-19, youTube.com

Native Range

Source: Kaschner, K., K. Kesner-Reyes, C. Garilao, J. Segschneider, J. Rius-Barile, T. Rees, and R. Froese. 2019. AquaMaps, Scarponi, P., G. Coro, and P. Pagano. A collection of Aquamaps native layers in NetCDF format.


As a general rule, do not eat ingredients that are not explicitly labeled for raw consumption.

This species is occasionally mislabeled or given misleading names. Apart from the potential health risks associated with mislabelling, it can also be a form of price fraud.

Consumption, especially of larger quantities, can cause digestive problems (keriorrhea). Keriorrhea is the production of greasy, orange-colored stool, which is caused by the consumption of indigestible wax esters. Persons with stomach or intestinal irritation should avoid consumption.

References & further reading

  • [Berman et al., 1981]: P. Berman, E. H. Harley, A. A. Spark. Keriorrhoea – the passage of oil per rectum – after ingestion of marine wax esters. South African Medical Journal Vol. 59 (22). Health & Medical Publishing Group. 1981
  • [Dodd et al., 2017]: Christine Dodd, Tim Grant Aldsworth, Richard A. Stein. Foodborne Diseases. Academic Press, Cambridge, Massachusetts, United States. 2017
  • [Froese & Daniel, 2019]: Rainer Froese, Pauly Daniel. FishBase. The Leibniz Institute of Marine Sciences at the University of Kiel, FishBase.org. 2019. Retrieved online on: December 24, 2020
  • [Kan et al., 2000]: Kimiko Kan, Hirofumi Ushiyama, Tetsuya Shindo, Shinichi Uehara, Kazuo Yasuda. Outbreak of Histamine Poisoning Due to Ingestion of Fish, "Abura-sokomutsu". Lepidocybium flavobrunneum. Journal of the Food Hygienic Society of Japan (Shokuhin Eiseigaku Zasshi, 食品衛生学雑誌) Vol. 42 (2). Japanese Society for Food Hygiene and Safety, Tokyo. 2000
  • [Levesque, 2010]: Juan C. Levesque. Evolving Fisheries: Today’s Bycatch is Tomorrow’s Target Catch - Escolar (Lepidocybium flavobrunneum) Catch in the U.S. Pelagic Longline Fishery. The Open Fish Science Journal Vol. 3 (1). Bentham Open, Sharjah. 2010
  • [Lowenstein et al., 2009]: Jacob H. Lowenstein, George Amato, Sergios Orestis Kolokotronis. The Real maccoyii: Identifying Tuna Sushi with DNA Barcodes – Contrasting Characteristic Attributes and Genetic Distances. PLOS One Vol. 4 (11). Public Library of Science, San Francisco. 2009
  • [MHLW, 2020]: Ministry of Health, Labour and Welfare (厚生労働省), www.mhlw.go.jp. Risk profile of natural toxins: Fish: abnormal lipids (自然毒のリスクプロファイル:魚類:異常脂質). https://www.mhlw.go.jp/topics/syokuchu/poison/animal_08.html
  • [NOAA, 2000]: National Oceanic and Atmospheric Administration, National Marine Fisheries Service. Draft Environmental Impact Statement Fishery Management Plan for Pelagic Fisheries of the Western Pacific Region: Environmental Impact Statement, United States.. Research Corporation of the University of Hawaii, URS Corporation, Honolulu. 2000
  • [Taylor, 2009]: Steve Taylor. Advances in Food and Nutrition Research, Academic Press. Academic Press, Cambridge, Massachusetts, United States. 2009
  • [Walker, 1998]: Harlan Walker. Fish: Food from the Waters, Proceedings Of The Oxford Symposium On Food And Cookery 1997. Prospect Books, London. 1998
  • [Warner et al., 2013]: Kimberly Warner, Walker Timme, Beth Lowell, Michael Hirshfield. Oceana Study Reveals Seafood Fraud Nationwide. Oceana Inc., Washington. 2013



Drawn illustration for  aburasokomutsu

Common names

escolar, black oilfish, snake mackerel

Japanese names

  • aburasokomutsu (アブラソコムツ)
  • sattou (サットウ)

Scientific name

Lepidocybium flavobrunneum


Snake mackerels or escolars


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