--- title: "Atlantic Halibut (Hippoglossus hippoglossus) | AnimalTracks.wiki" description: "The world's largest flatfish, and a fish that moves one of its eyes across its head." image: "https://animaltracks.wiki/images/animals/atlantic-halibut-1.webp" published: "2026-10-11" updated: "2026-10-11" --- # Atlantic Halibut (*Hippoglossus hippoglossus*) > **Status**: Checked against 5 sources, listed under Sources below. > **Tagline**: The world's largest flatfish, and a fish that moves one of its eyes across its head. > **Soundtrack Vibe**: Sludge Metal & Abyssal Doom // Windhand, "Orchard" > **Soundtrack Links**: [Spotify](https://open.spotify.com/track/3bZG5LMoqBiXDwSSi2p2VN) > **Vibe Match**: The Atlantic halibut is the largest flatfish in the world, lives mostly on the bottom as an adult and takes about 10 years to mature, with a metamorphosis that is drawn out. Windhand's Orchard is doom at the same scale and pace, built from huge, slow, downtuned riffs. ## Biological Superpowers & Stats - **Taxonomy**: *Hippoglossus hippoglossus* - **Danger Level**: Low - **Conservation Status**: Near Threatened ([IUCN Red List](https://doi.org/10.2305/iucn.uk.2022-2.rlts.t10097a148035632.en)) - **Superpower**: Moves an eye to the other side of its head during metamorphosis - **Habitat**: Sand, gravel and clay seabed of the northern Atlantic, 160 to 6,560 feet down - **Diet**: Invertebrates when small; almost exclusively fish from about 31 inches long - **Tags**: fish, ocean, benthic, predator, giant-size ## Natural History & Behavior ## One eye on the move The Atlantic halibut is a flatfish, and in flatfishes eye migration is the metamorphic process (a change in body form) whereby one eye migrates to the other side of the head. The retina is restructured too: the larva's hexagonal lattice of single cones gives way to a mostly square mosaic of four double cones around each single cone. Cones are light-sensing cells in the eye. The skull is involved too: in halibut larvae, the frontal bone shows torsion (a twist) correlated with eye migration, though its full hardening into bone is independent of the eye's move. Researchers raising larvae also note that metamorphosis is protracted in halibut, meaning it is drawn out. The adult ends up as a right-eyed flounder. NOAA tells it from other right-eyed flounders by its size, a concave tail fin, a large gaping mouth and an arched lateral line. It is uniformly dark brown or black, while young fish are marbled or spotted with paler marks. Its genus name comes from Greek for "horse tongue". > **Cape Ann giant** > The largest Atlantic halibut on record was taken off Cape Ann, Massachusetts, and weighed 615 pounds gutted with the head still attached. NOAA estimates it weighed about 700 pounds alive. ## Built big, built slow NOAA calls it the largest species of flatfish in the world, and says it can reach up to 15 feet in length. Full-grown females average 100 to 150 pounds, and males tend to be smaller. NOAA calls it a long-lived, late-maturing species: it can live up to 50 years, and the average age at maturity is about 10 years. FishBase gives 7 to 8 years for males and 10 to 11 for females. FishBase notes that with slow growth and late maturity, halibut populations can be seriously affected by overfishing. ## A menu that grows with it Small halibut, up to about 12 inches long, feed almost exclusively on invertebrates. The proportion of fish in the diet increases as they grow, and by roughly 31 inches they eat almost exclusively fish. FishBase says they feed mainly on cod, haddock, pogge, sand-eels, herring and capelin, but also take cephalopods and large crustaceans. Adults are benthic, meaning they live on the bottom, though they are occasionally pelagic (up in open water). They live on or near sand, gravel or clay at depths of 160 to 6,560 feet. The range runs from Labrador and Greenland to Iceland, and from the Barents Sea south to the Bay of Biscay and Virginia. In U.S. waters, they are most common in the Gulf of Maine. ## Fished down The IUCN Red List rates the species Near Threatened, in an assessment from 2021. In U.S. waters, NOAA's 2024 stock assessment found the stock overfished. A rebuilding plan has a target date of 2055. In 2024, U.S. commercial landings totalled 76,000 pounds, valued at about $480,000, and federal waters have a limit of one fish per vessel per trip. ## Frequently Asked Questions ### How big does an Atlantic halibut get? Up to 15 feet long, says NOAA. An average full-grown female weighs 100 to 150 pounds. The record fish, landed off Cape Ann in Massachusetts, weighed 615 pounds with its guts removed and probably about 700 pounds alive. *(Source: [NOAA Fisheries]())* ### How does a halibut end up with both eyes on one side? It happens during metamorphosis, a big change in body form. In flatfishes this is called eye migration: one eye travels across to the other side of the head. The retina is restructured along the way, with the larva's hexagonal pattern of single cone cells giving way to a mostly square one. *(Source: [Bolstad & Novales Flamarique 2022]())* ### How long do Atlantic halibut live? Up to 50 years, according to NOAA. They are slow to breed as well: on average they mature at about 10 years old. *(Source: [NOAA Fisheries]())* ### What does an Atlantic halibut eat? It depends on size. Halibut up to 12 inches long eat almost exclusively invertebrates. The share of fish in the diet climbs as they grow, until at approximately 31 inches they eat almost exclusively fish. *(Source: [NOAA Fisheries]())* ## Sources 1. [Atlantic Halibut. NOAA Fisheries.]() 2. [Hippoglossus hippoglossus summary page. FishBase.]() 3. [Bolstad & Novales Flamarique (2022). Chromatic organization of retinal photoreceptors during eye migration of Atlantic halibut (Hippoglossus hippoglossus). Journal of Comparative Neurology.]() 4. [Sæle et al. (2004). Staging of Atlantic halibut (Hippoglossus hippoglossus L.) from first feeding through metamorphosis, including cranial ossification independent of eye migration. Aquaculture.]() 5. [Cadrin et al. (2022). Hippoglossus hippoglossus. The IUCN Red List of Threatened Species 2022: e.T10097A148035632.]() *Published October 11, 2026. 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