Oilfish

Oilfish in trade usually combines two closely related deepwater species of the Gempylidae family: smooth skin (SS) oilfish and escolar Lepidocybium flavobrunneum and rough skin (RS) oilfish - Ruvettus pretiosus. Both are large, dark-fleshed predators from tropical and temperate oceans. However, they are not the same fish. Escolar is generally the smoother-skinned species, occurring mainly over the continental slope and migrating upward at night, while Ruvettus pretiosus is a rougher-skinned deepwater species that is more often associated with shelf and slope waters and is usually found
solitary or in pairs. In commercial practice, the two are often grouped together because both are caught mainly in longline fisheries and marketed in similar formats, especially as frozen HGT, fillets and steaks.

From an eating-quality perspective, oilfish is highly appreciated for its rich, buttery taste, high fat content, and soft, succulent flesh. This is exactly why it has long attracted premium niche demand in foodservice and in steak-style presentations. However, the same quality that gives oilfish its luxurious mouthfeel is also its main limitation. Both species contain very high levels of indigestible wax esters, sometimes referred to in food safety guidance as gempylotoxins.

These wax esters may cause ceriorhea, abdominal cramps, nausea, headache, and vomiting, particularly when eaten in larger portions or by sensitive individuals. In practical market terms, this means oilfish is a species with strong culinary appeal but one that must be sold responsibly, with proper product knowledge and portion awareness. Commercially, oilfish is positioned as a niche premium deepwater species, not a mass-market whitefish or tuna substitute. It is typically sold fresh or frozen in HGT, fillets, chunks, and steaks, and in some markets escolar has been used in fish cakes or high-end restaurant applications. 

Because of its wax-ester issue, however, the product remains controversial in some markets and requires clear identification and correct commercial communication. The main fishing nations vary by ocean area, because neither species supports a single classic directed global fishery in the way tuna or mackerel do. Much of the supply comes as bycatch in tuna longline fisheries, while some directed deepwater fisheries also exist. FAO notes oilfish and escolar among the many bony fishes caught in pelagic longline fisheries, and the 2025 SIOFA overview shows that, in the Southern Indian Ocean, targeted oilfish catches were almost entirely taken by Chinese Taipei. In broader market terms, oilfish supply is linked to longline-producing countries (Vietnam, Taiwan, Indonesia) and deepwater fleets in the Indian, Pacific, and Atlantic Oceans, while demand is strongest in selected premium and foodservice markets rather than mainstream retail.