Japan has banned escolar as food since 1981, yet sushi counters elsewhere keep serving it, often as “white tuna” or butterfish. It is a deep-water snake mackerel with buttery white flesh, and it lands on plates as nigiri or sashimi. The wax esters in that flesh are indigestible, and in some diners they cause oily orange discharge.
Health Canada (updated April 2026) states that gempylotoxin, the wax ester oil in the flesh, is not toxic to humans despite its name. The oil is simply indigestible, and the laxative effect it causes in some people ends within 24 to 48 hours, according to Health Canada.
What Is Escolar Sushi?
Escolar reaches the sushi counter as nigiri or sashimi, cut from a deep-water snake mackerel with rich white flesh that restaurants often sell as “white tuna”. The fish stores indigestible wax esters in that flesh, which is why some diners end up with oily orange discharge and why Japan banned it.
The species is Lepidocybium flavobrunneum, part of the Gempylidae family (snake mackerels). It is closely related to the scombroid fishes, but it is not a tuna. Oilfish (Ruvettus pretiosus) is a separate species with the same wax esters, and Health Canada’s fact sheet uses “escolar” for both. The name is Spanish for “scholar”, after the spectacle-like rings around the eyes (Collins English Dictionary).
Escolar became a menu fish only after longline boats started fishing deeper for tuna and swordfish and landing it as bycatch (Mother Jones, 2009).
These days a slice of it usually arrives as hand-pressed nigiri, or cut plain as sashimi.
FishBase records the species at 200 to 1,100 m depth in tropical and temperate seas worldwide, reaching 200 cm standard length.
What Does Escolar Sushi Taste Like?
Mild, buttery and a little sweet. The texture is silky, and diners often compare it to tuna.
That richness earned it nicknames like “butterfish” and “white toro”, a nod to toro, the fatty tuna belly cut. The flesh is opaque white with no pink in it. The bite is firm but tender, and there’s a butter-like smell with a faint sweetness behind it.
Health Canada says the muscle can hold about 20% oil by weight, and CSIRO data cited in Communicable Diseases Intelligence (2002) give the same figure. That oil explains the texture.
Because the flavor needs no help, many counters serve it as plain sashimi slices with nothing but soy and wasabi.
Rich and cheap, and easy enough to like. The same oil that makes it taste this good is the one humans cannot digest.
Why Does Escolar Cause Keriorrhea?
Escolar cannot metabolize the wax esters in its diet, so the fish stores them as oil throughout its flesh. People cannot break the esters down either. The unabsorbed oil passes through the gut as oily orange discharge called keriorrhea (Greek for “flow of wax”).
Wax ester content in escolar flesh
Health Canada puts the indigestible oil at about 20% of muscle weight. Australia’s Communicable Diseases Intelligence (2002) and Germany’s BfR (2003) both put wax esters at 90% or more of that oil.
Multiply the two and wax esters make up roughly 18% of the flesh, or slightly more. That 18% is calculated from the two figures, not reported by either source. The figures measure different layers (oil in the flesh, wax ester in the oil), so they do not contradict each other.
Symptoms and timing
The FDA lists diarrhea, abdominal cramps, nausea, headache and vomiting as the effects of gempylotoxin, its name for the wax esters. The signature symptom is oily orange discharge, which is where the “Ex-Lax fish” nickname comes from.
Symptoms can start anywhere from 30 minutes to 36 hours after eating (NSW Food Authority). Not everyone reacts, though. Health Canada notes that not every diner develops symptoms, and the FDA says the quantity needed to cause effects is unknown and varies with individual sensitivity.
NSW Food Authority calls the condition neither ongoing nor life threatening.
Do wax esters explain every case?
The indigestible oil is the leading explanation, and it matches the symptom pattern well.
Germany’s BfR (2003) was less settled and said it was not yet clarified whether wax esters are the only cause. It listed allergenic fish proteins and histamine from long storage as other candidates. The FDA’s August 2019 guidance independently links improperly handled escolar to histamine (scombrotoxin) poisoning, so a bad reaction does not always trace back to the wax alone.
Is Escolar Banned? Country-by-Country Status
Japan banned escolar as food in 1981 (and oilfish in 1970), according to its Ministry of Health, Labour and Welfare, although many English-language sources give 1977. Most other regulators stop at advice, packaging or labeling rules, and sources disagree on Italy.
| Jurisdiction | Status | Date | Source |
|---|---|---|---|
| Japan | Banned as food | 1981 (oilfish: 1970) | Ministry of Health, Labour and Welfare |
| Italy | Reported ban; also reported as allowed | 2007 report; 2013 report | CFS; Il Fatto Alimentare |
| United States | Advice against import and interstate sale | August 2019 guidance | FDA |
| Canada | Legal to sell, with portion and labeling advice | Current fact sheet | Health Canada |
| European Union | Packaged and labeled only | 17 October 2008 | Regulation (EC) 1020/2008 |
| Hong Kong | Oilfish: trade agreed to stop import and sale | January 2007 | Centre for Food Safety |
| Australia (NSW) | Legal to sell, correct labeling required | Current advisory | NSW Food Authority |
Dates show when each source recorded the position.
In the United States, the FDA’s Hazards and Controls Guidance (Chapter 6, August 2019) advises against importing and marketing escolar and oilfish across state lines. The same chapter says the agency has no specific expectations for controls in processors’ HACCP plans, so the position is advice, not a prohibition.
Japan treats escolar as toxic. Health Canada says it does not pose a health risk, and NSW Food Authority calls the effect not life threatening. They all describe the same mechanism, so the disagreement is about severity, not science.
Italy is murkier. Hong Kong’s Centre for Food Safety listed it alongside Japan as banning the import and sale of oilfish and escolar in its February 2007 Food Safety Focus bulletin, and the claim has been repeated in Lowenstein et al. (2009) and Oceana’s 2013 report. The Italian trade outlet Il Fatto Alimentare reports the opposite, that Italy chose to allow sale of packaged, labeled product because the market values the white, flavorful flesh. That fits the EU rule above, which covers all member states. Neither source cites an Italian statute on the ban itself.
Mislabeling, not the fish itself, usually triggers action. In January 2007 the Centre for Food Safety investigated 14 complaints of upset stomachs after the supermarket chain PARKnSHOP sold oilfish labeled as codfish.
Within two days the centre had logged over 100 complaints and enquiries, and importers, wholesalers, retailers and caterers agreed to stop importing and selling the fish (Centre for Food Safety, 2007).
Why Escolar Is Sold as White Tuna, and How to Spot It
“White tuna” on a sushi menu can mean albacore or escolar, and DNA tests keep finding escolar. The swap pays because escolar costs far less than tuna (New York Senate bill S6842B).
Oceana’s 2013 national report found that 84% of the “white tuna” samples it tested were escolar.
A 2009 PLoS ONE study of sushi restaurants in Manhattan and Denver found escolar in five of nine samples sold as a variant of white tuna (Lowenstein et al.).
Student DNA testing at Dominican University, reported in 2025, turned up escolar in seven white and “super white” tuna samples from restaurants.
The rates differ because the samples do. Oceana sampled retail outlets nationwide, while the 2009 team bought tuna orders in two cities, so a small count swings the percentage.
Selling escolar is legal in the US. Lowenstein and colleagues (2009) said the white tuna swap was not an unambiguous case of economic fraud under existing rules, although they still classed it as a misrepresentation. New York has since changed that for its own market.
On labeling, FDA’s Regulatory Fish Encyclopedia lists “escolar” as the market name for Lepidocybium flavobrunneum. Hawaii’s health department has gone after establishments that sold escolar as butterfish, according to KHON2.
New York’s S6842B, signed in September 2016, makes it unlawful to willfully sell escolar or oilfish as tuna, albacore tuna or white tuna. The law took effect in January 2017 (SeafoodSource).
| Menu name | Can really be | Quick check |
|---|---|---|
| White tuna, super white tuna | Albacore or escolar | Pink or beige tint means albacore |
| Shiro maguro | Albacore, sometimes escolar | Ask for the species |
| Butterfish | Sablefish, silver pomfret or escolar | Ask for the Latin or Japanese name |
| Walu, waloo | Escolar | Treat as escolar |
| Rudderfish, sea bass, blue cod | Escolar or oilfish | Ask for the species |
Health Canada’s fact sheet lists gemfish, rudderfish, butterfish, sea bass, blue cod, ruddercod and walu among the names used for mislabeled escolar and oilfish. Sablefish also trades as butterfish, so the word alone proves nothing.
The simplest check is to ask for the species name instead of the menu name. Color helps a little too. Raw albacore runs from light beige to almost brown (SeafoodSource Seafood Handbook, 2014), while milky white points to escolar. And if a menu says “white tuna” with no species named, treat it as unconfirmed.
How Much Escolar Is Safe to Eat?
No tested safe amount exists. The common guideline is under 6 oz (170 g), and Health Canada says the available data cannot support a fixed intake level.
Hawaii’s health department recommends less than six ounces of walu or escolar (KHON2). Hawaii has no ban, and a 2010 bill that proposed one (H.B. 2669) used the same figure, stating that more than six ounces can cause severe diarrhea.
Health Canada puts the average adult finfish portion at 150 g. An ordinary fish serving already sits just under the 170 g guideline, and a larger sashimi order passes it.
The guideline is also a convention, not a measured threshold. Health Canada reports that individual differences in sensitivity have not been characterized, so a safe amount for one diner can be too much for another.
- Confirm the fish is escolar and not an unnamed “white tuna”.
- Order a small first portion, which is Health Canada’s advice for anyone new to escolar. What counts as small varies by person.
- Keep the whole meal under 6 oz (170 g) of escolar.
- Skip it if you are pregnant, a child, elderly, or have bowel or absorption problems. Health Canada advises these groups to avoid it.
Health Canada says heating does not change gempylotoxin, though cooking that drains the oil, such as grilling, may reduce the onset or size of symptoms. NSW Food Authority says no cooking or handling practice prevents keriorrhoea.
For raw nigiri and sashimi the dispute is moot, because nothing drains the oil.
Which Fish Make a Safer Substitute for Escolar?
Hamachi comes closest to escolar’s richness, albacore is the genuine white tuna, and sablefish works best cooked. The FDA’s August 2019 natural toxins guidance names escolar and oilfish as the fish carrying high concentrations of gempylotoxin wax esters and notes lesser amounts in orange roughy and oreo dory. None of these substitutes is named as a source of the wax esters.
Hamachi, the closest match in richness
Hamachi is young Japanese amberjack (Seriola quinqueradiata), usually farmed, with a mild, buttery flavor and firm texture. If it is new to you, this overview of what hamachi sushi actually is covers the cuts and flavor.
It is rich and buttery like escolar, with a firm bite, and farmed fish carry consistently high fat.
Menu names are the annoying part. Hamachi, kanpachi and yellowtail are three different fish, which makes the labels unreliable (PBS Food). There is an environmental catch as well. Seafood Watch’s 2008 sushi guide put farmed Japanese and Australian yellowtail on “Avoid” over environmental impact and heavy reliance on wild-caught fish in feed, so check the current rating.
Albacore, the genuine white tuna
FDA and EPA place albacore in the “Good Choices” mercury tier (advice revised October 2021), which caps intake for people who are pregnant, breastfeeding or feeding young children.
The taste is mild and rich, the texture firm and steaky, and the meat is the lightest of any tuna (SeafoodSource Seafood Handbook, 2014). U.S.- and Canada-caught albacore, sold as shiro maguro, was among the alternatives the 2008 sushi guides recommended.
On the downside, the same handbook calls it less firm than yellowfin or bluefin and less suited to sashimi, although Hawaii’s seafood council lists raw sashimi among suggested preparations. That mercury tier applies too.
Sablefish, rich but mostly cooked
Sablefish is the buttery fish also sold as black cod and gindara. It is soft, white, mild and rich in oil, and Seafood Watch gives it a “Best Choice” rating for pot-caught US West Coast fish and one farm in British Columbia. Japan serves it raw as sushi under the name gindara.
Most people know it cooked, though, as Nobu Matsuhisa’s miso-marinated black cod (Saveur), so raw menu options are scarcer. It also lands in FDA and EPA’s “Good Choices” mercury tier, and it trades as “butterfish”, the same word escolar hides behind.
Escolar Sushi FAQ
Does escolar contain mercury?
Yes. Health Canada says escolar, like other predatory fish, carries relatively elevated mercury levels.
The agency has set a 1.0 ppm mercury standard and issued consumption advice covering escolar and other predatory fish.
Can escolar cause dehydration?
Health Canada says no. Keriorrhea is not associated with a loss of bodily fluids, and the same fact sheet calls the reaction short-lived and not life threatening.
Is escolar overfished?
It depends who you ask. A 2010 study of the US pelagic longline fishery in the western North Atlantic found stable catch rates, which suggests overfishing is not occurring there.
The Dutch Good Fish Foundation’s 2024 rating goes the other way for the global longline fishery. It rates escolar red, citing heavy fishing pressure and an unmanaged fishery.
What is escolar called in Japanese?
Aburasokomutsu. Japanese sushi references use that name for escolar, while its relative the oilfish is called barramutsu.
They also point out that, despite the “butterfish” label sometimes attached to it, the fish belongs to the snake mackerel family.
Should You Order White Tuna When No Species Is Named?
Pass on any white tuna order when the server cannot name the species. Escolar sushi is the fish behind that label more often than albacore, and the menu wording gives no way to tell the two apart.
Passing costs one menu item and the chance to try escolar on purpose. Ordering blind costs the ability to control the portion.
New York’s S6842B, introduced in February 2016 and signed that September, took effect in January 2017. It defines white tuna as albacore and bars willfully selling escolar or oilfish under the name tuna, albacore tuna or white tuna (SeafoodSource, 2017).
Outside jurisdictions with a rule like that, the label carries no species guarantee, so this advice holds until menus must print the species name. Position verified October 21, 2026.
