The escolar, Lepidocybium flavobrunneum, is a snake mackerel, the only species in the genus Lepidocybium. It is found in deep (200–885 m) tropical and temperate waters around the world.

It is also marketed as "butterfish".


The escolar is dark brown in colour, growing darker with age until it is quite black. It is a fast-swimming fish with a prominent lateral keel and multiple finlets. It grows up to 2 m in length.


Escolar is consumed in several European and Asian countries, as well as in the USA, sometimes raw as sushi or sashimi. It may be sold as "white tuna" - a term also used for the albacore - or as "super white tuna" to distinguish it from the albacore. Escolar is also sold misleadingly as "butterfish", "oilfish" and "Hawaiian butter fish"; in Hawaii and Fiji, it is known as walu. Like oilfish, a related species with similar consumption consequences, escolar is also sometimes deceptively sold under the name of an entirely different species of fish, most commonly "codfish" or "orange roughy".

Effects of consumption

Like its relative the oilfish (Ruvettus pretiosus), it cannot metabolize the wax esters (Gempylotoxin) naturally found in its diet, which accumulates to give an oil content in the muscle meat of 18–21%. These wax esters may rapidly cause gastrointestinal symptoms following consumption; however, these effects are usually short lived.

The gastrointestinal symptoms, called "keriorrhoea", caused by these wax esters may include oily orange diarrhea, discharge, or leakage from the rectum that may smell of mineral oil. The discharge can stain clothing and occur without warning 30 minutes to 36 hours after consuming the fish. The oil may pool in the rectum and cause frequent urges for bowel movements due to its lubricant qualities and may be accidentally discharged by the passing of gas. Symptoms may occur over a period of one or more days. Other symptoms may include stomach cramps, loose bowel movements, diarrhea, headaches, nausea, and vomiting.

To minimize the risk of symptoms, strict control of portion size is recommended as well as preparation methods that remove some of the oil (e.g. grilling). Portions should be no greater than 6 ounces.


For these reasons, escolar has been banned from consumption in Japan since 1977, as the Japanese government considers it toxic. It has also been banned in Italy. In 1999, the Swedish and Danish National Food Administrations informed fish trade associations and fish importing companies about the problems escolar and related fish could cause if not prepared properly and issued recommendations.

In early 2007 after a public outcry and receiving consumer complaints about mislabeled fish and conducting an investigation, the Hong Kong government's Centre for Food Safety recommended that escolar not be used for catering purposes, advised clear labeling and identification of fish species before sale, purchase of fish from reliable sources, and recommended that consumers become aware of the possible health effects of consumption of escolar, oilfish, and related species. The Hong Kong government has established a working group comprised of members of the academia, trade and consumer group to prepare guidelines for assisting the trade and consumers in identifying relevant species of fish.

In the United States, the U.S. Food and Drug Administration, after receiving complaints about diarrhea associated with escolar consumption, issued a bulletin recommending against import of the fish in the early 1990s. However, the FDA backed away from this recommendation and withdrew the bulletin several years later after deciding the fish was nontoxic and nonlethal. Currently, the FDA informally recommends that "Escolar should not be marketed in interstate commerce.

In mid-2007, the Canadian Food Inspection Agency, after investigating cases of diarrhea caused by mislabeled fish, decided not to ban escolar or oilfish but instead issued a fact sheet noting the potential adverse effects of consumption and recommending that consumers speak with their retailer, verify fish species and consume the fish in small portion size using preparation methods that reduce oil content.



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