Bastard Halibut

Bastard halibut is an alternate common name for the olive flounder, a large left-eyed flatfish in the family Paralichthyidae native to the coastal waters of Japan, Korea, and China. The name "bastard halibut" arose in some English-language fisheries and trade contexts to distinguish this species from true halibut, to which it is not closely related despite superficial size and shape similarities. It is a demersal, sand-dwelling species with a broad, muscular body and large mouth adapted for capturing fast-moving prey. The species is one of the most significant marine flatfish in East Asian aquaculture, with extensive farming operations supplementing wild coastal populations across its native range.

• Broad, oval, muscular body typical of large predatory flatfish
• Eyes positioned on the left side of the head
• Upper side is olive-brown to dark brown with numerous small dark and pale spots
• Large mouth with prominent teeth, extending past the rear edge of the eye
• Underside is white, occasionally blotched in larger individuals
• Adults commonly reach 40-70 cm, with large individuals approaching 1 m

Despite the common name, its overall body proportions and moderate size distinguish it from true halibut species (genus Hippoglossus), which grow substantially larger and have a more elongated, diamond-shaped outline.

Bastard halibut (olive flounder) occur along the coasts of Japan, the Korean Peninsula, and China, including the Yellow Sea and East China Sea. They live on sandy or sand-mud seafloor in coastal and estuarine waters, from shallow nearshore depths down to roughly 100-200 meters. Juveniles typically use shallow, sheltered coastal habitats and estuaries as nursery grounds before moving into deeper offshore waters as adults, and the species is well adapted to the temperate coastal conditions found throughout its native East Asian range.

Bastard halibut are active ambush predators that partially bury themselves in sandy substrate and wait for prey, mainly small fish, shrimp, and crabs, before striking with a rapid burst of speed. Outside of hunting bursts, they are relatively sedentary, conserving energy while camouflaged against the seafloor. Like other flatfish, they begin life as symmetrical, free-swimming larvae before undergoing eye migration and settling onto the bottom as juveniles. The species is heavily cultured in aquaculture facilities across East Asia, and farmed populations are managed alongside wild stocks that continue to reproduce naturally along the region's sandy coastlines.