The escolar, Lepidocybium flavobrunneum, a species of fish in the family Gempylidae, is found in deep (200–885 m) tropical and temperate waters around the world. It is also known as snake mackerel, and is sometimes fraudulently marketed as "butterfish" or "white tuna", a controversial practice due to potential health problems related with consumption of the fish.
The escolar is dark brown, growing darker with age until it is quite black. It is a fast-swimming fish with a prominent lateral keel and four to six finlets after the anal and second dorsal fins. Escolar can grow to over 2 m in length. Like its relative the oilfish (Ruvettus pretiosus), escolar cannot metabolize the wax esters (gempylotoxin) naturally found in its diet. This gives the escolar an oil content of 14–25% in its flesh.
Health effects 
Escolar's wax ester content can cause keriorrhea (Greek: flow of wax), gempylotoxism or gempylid fish poisoning. Keriorrhea is similar to diarrhea, only the body will expel yellowish-orange drops of oil instead of liquid bowel movements. Some individuals suffering from escolar-induced keriorrhea also report other digestive issues, including stomach cramps, diarrhea, headaches, nausea, vomiting, and anal leakage; onset may occur between 30 minutes and 36 hours following consumption. This condition may also be referred to as steatorrhea.
Two known ways to reduce the likelihood of escolar-induced keriorrhea are to limit portions to six ounces or less and to consume portions close to the tail, which typically have a lower wax ester content. Reports conflict on whether deep skinning, freezing or grilling will reduce the likelihood of keriorrhea.
Escolar can be mislabeled in both restaurants and at fish markets. In 2009, as part of a project to create a DNA database of every fish species, scientists from Columbia University and the American Museum of Natural History tested tuna samples from sushi restaurants in New York City and Denver, Colorado. They discovered five of nine restaurants serving fish labeled “white tuna,” “white tuna (albacore)” or “super white tuna” were actually serving escolar. From 2010 to 2013, a study by Oceana tested over 1,200 samples of fish from 671 retail outlets in 21 states, and found that 84% of the white tuna samples were actually escolar.
Escolar has been mislabeled or otherwise confused with the following fish: Atlantic cod, oilfish (related to escolar but in a different genus), rudderfish, blue cod, black cod, king tuna, grouper, orange roughy, sea bass, gemfish, Chilean sea bass, albacore tuna, and white tuna.
Escolar is also known as butterfish (incorrectly), Hawaiian butterfish, walu/waloo, or super white tuna.
This mislabeling, whether by ignorance or deceit, is more hazardous than the mislabeling of other fish due to the potential health effects of escolar.
Regulation and banning 
Italy and Japan have banned the sale of escolar due to its potential side effects. It has been banned from consumption in Japan since 1977, as the Japanese government considers it toxic. 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, receiving consumer complaints about mislabeled fish and conducting an investigation, the Hong Kong government's Centre for Food Safety recommended escolar not be used for catering purposes, advised clear labeling and identification of fish species before sale, and purchase of fish from reliable sources, and recommended 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 composed 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 FDA, 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, "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 consumers speak with their retailer, verify fish species and consume the fish in small portion sizes using preparation methods that reduce oil content.
- Mims, Christopher (2013-02-22). "59% of the 'Tuna' Americans eat is Not Tuna". The Atlantic. Retrieved 22 Feb 2013.
- Lowrey, Annie (2010-04-26). "The List: Food Fights". Foreign Policy. Retrieved 31 March 2011.
- Escolar, Lepidocybium flavobrunneum (Smith, 1849)
- "Gempylotoxin" Foodborne Pathogenic Microorganisms and Natural Toxins Handbook (Bad Bug Book). U.S. Food and Drug Administration's Center for Food Safety and Applied Nutrition, January 2008.
- Hong Kong Centre for Food Safety, "Risk in Brief: Oily Diarrhoea (Keriorrhoea) after Fish Consumption" (March 2007)
- Plos One: accelerating the publication of peer-reviewed science, 2009, "The Real maccoyii: Identifying Tuna Sushi with DNA Barcodes – Contrasting Characteristic Attributes and Genetic Distances"
- "National Seafood Fraud Testing Results Highlights". Oceana Report. 2013-02-21. Retrieved 22 Feb 2013. Text "Oceana" ignored (help)
- Medellitin, 2008, "Escolar: The World's Most Dangerous Fish"
- Burros, Marian (March 10, 1999). "A Fish Puts Chefs in a Quandary". New York Times. Retrieved 31 March 2011.
- European Food Safety Authority, "Opinion of the Scientific Panel on Contaminants in the Food Chain on a request from the Commission related to the toxicity of fishery products belonging to the family of Gempylidae" (August 2004)
- Hong Kong Centre for Food Safety, "Food Alerts: Complaints of Oily Diarrhoea after Consuming Certain Types of Marine Fish" (March 2007)
- U.S. Food and Drug Administration Center for Food Safety and Applied Nutrition, April 2006, "Managing Food Safety:A Manual for the Voluntary Use of HACCP Principles for Operators of Food Service and Retail Establishments, Annex 2 (Seafood References)"
- Escolar and Adverse Reactions
- RELATING TO WALU
- HB2669 Status