Halibut Halibut Halibut is a common name principally applied to the two flatfish in the genus "Hippoglossus" from the family of right-eye flounders. Less commonly, and in some regions only, other species of flatfish are also referred to as being halibuts. The word is derived from "haly" (holy) and "butte" (flat fish), for its popularity on Catholic holy days. Halibut are demersal fish and are highly regarded as a food fish. The Pacific halibut is the world's largest flatfish. The IGFA record was apparently broken off the waters of Norway in July 2013 by a 515-pound 8.6 foot fish. This was
Fish anatomy Their retinas generally have both rod cells and cone cells (for scotopic and photopic vision), and most species have colour vision. Some fish can see ultraviolet and some can see polarized light. Amongst jawless fish, the lamprey has well-developed eyes, while the hagfish has only primitive eyespots. The ancestors of modern hagfish, thought to be the protovertebrate were evidently pushed to very deep, dark waters, where they were less vulnerable to sighted predators, and where it is advantageous to have a convex eye-spot, which gathers more light than a flat or concave one. Unlike humans, fish normally adjust focus by