Halibut are the largest members of the flatfish family Pleuronectidae, characterized by their unique diamond shape and both eyes positioned on the upward-facing side of their body. These demersal fish primarily inhabit the cold, deep waters of the North Pacific and North Atlantic Oceans, spending most of their time on or near the ocean floor. Their immense size potential makes them a highly sought-after species for both commercial and recreational fishing.
The Two Halibut Species
The discussion of halibut size centers on two species: the Pacific Halibut (Hippoglossus stenolepis) and the Atlantic Halibut (Hippoglossus hippoglossus). The Pacific species is found along the continental shelf from California to the Bering Sea. This population is currently managed under robust international stewardship programs, maintaining a relatively healthy stock and representing the most common source of large catches today.
The Atlantic Halibut inhabits the North Atlantic, stretching from the northeastern U.S. and Canada to Northern Europe. Historically, the Atlantic species was considered the largest, but severe overfishing has depleted its stocks, classifying it as endangered in many areas. Because of these management differences, the Pacific halibut dominates the modern market and holds the current attention of anglers seeking massive specimens.
Maximum Potential Size and Records
The maximum potential size of halibut is colossal, earning the largest fish the nickname “barn doors” due to their width. The International Game Fish Association (IGFA) all-tackle world record for the Pacific Halibut stands at a massive 459 pounds, caught off Dutch Harbor, Alaska, in 1996. These gigantic specimens can reach lengths exceeding eight feet and widths of more than five feet.
Unverified reports and historical accounts suggest Pacific Halibut have been caught weighing up to 533 pounds, and a few commercial hauls have documented fish nearing 500 pounds. Atlantic Halibut holds the historical claim to the greatest size, with records suggesting individuals in the past reached weights of 700 pounds or more, although these older figures are often not thoroughly documented. More recent large Atlantic catches include a 515-pound fish caught in Norwegian waters in 2013, which remains one of the largest verifiable specimens from either ocean.
Growth Rates and Lifespan
Halibut achieve their immense size through slow, continuous growth and extraordinary longevity. Females of both species grow significantly faster and larger than males, with males rarely exceeding 80 to 100 pounds. The age of a halibut is determined by counting the growth rings found on its otolith, a bony structure in the inner ear.
The lifespan of a Pacific Halibut typically ranges from 25 to 35 years, though the oldest recorded individual lived to be 55 years old. Atlantic Halibut are even longer-lived, with some females surviving for 50 years or more. This extended lifespan allows female halibut to accumulate hundreds of pounds of mass over decades.
Typical Sizes Encountered
The average size of a halibut encountered by fishers or seen in markets is significantly smaller than the record-breaking giants. In the commercial fishery, the majority of harvested Pacific Halibut weigh between 10 and 50 pounds. A common industry term for smaller halibut is “chicken halibut,” which typically refers to fish under 10 pounds.
The average weight of commercially landed Pacific Halibut in recent years has often been around 22 pounds, a decrease from the 30- to 40-pound averages seen decades ago. Recreational anglers typically catch fish in the 15- to 20-pound range, but fish up to 150 pounds are regularly landed. Fishing regulations often impose size limits designed to protect the largest and oldest females, since these individuals produce the most eggs, which influences the size distribution of fish available for harvest.