BIOLOGY & LIFE CYCLE
Wild Pacific halibut are highly migratory fish found along the continental shelf in the North Pacific Ocean and Bering Sea. They are known for their large size, camouflaged flat bodies, active nature and bottom dwelling habits. They are perhaps most distinguished by both eyes positioned on the dark, top side of their head.
Flat out Facts
FAST FACTS
GENUS & SPECIES:
Hippoglossus stenolepis
FAMILY:
Pleuronectidae
APPEARANCE:
Distinguishing features include:
• large flat, thick and sturdy diamond-shaped body
• mottled green, black or brown skin on the top, dorsal side and bright white skin on the underside
• small scales that are buried in its skin giving it a smooth appearance
• both eyes are on the dark, top side of its head
• almost always right-eyed
• large mouth with sharp conical teeth
AGE:
• Females live longer than males
• Oldest recorded female in Canada was 42 years old and the oldest male was 27 years old
HABITAT
• Highly migratory fish
• Found along the continental shelf in the North Pacific Ocean and Bering Sea, and as far west as Japan and Russia
• Typically dwell at ocean depths between 75 and 500 metres (250 and 1,800 feet)
• Can dwell as deep as 1,220 metres (4,000 feet)
SIZE & WEIGHT
• Wild Pacific halibut are one of the largest flatfish
• Can grow to a maximum length of about 2.5 metres (8 feet)
• Can weigh up to 227 kilograms (500 pounds) of round weight (whole), which translates into 170 kilograms (375 pounds) of net dressed weight* (eviscerated, head-off)
*Note: Net dressed weight is the standard reporting practice for wild Pacific halibut.
LEGAL COMMERCIAL SIZE:
Wild Pacific halibut must be larger than the regulated minimum size in order to be harvested by commercial fishermen.
24 inches (61 cm): head-off OR 32 inches (81.3 cm): head-on
LIFE CYCLE
• Wild Pacific halibut spawn in deep water where females will lay between 500,000 to 4 million eggs depending on their size. Female wild Pacific halibut are usually 10 to 12 years old when they spawn and males are usually about eight when they reach sexual maturity.
• Each fertilized halibut egg, or embryo, floats through the water and after about 10 to 20 days hatches into a larva.
• The larva drifts slowly upward in the water column travelling great distances with the ocean currents in a counter-clockwise direction in the Gulf of Alaska using its yolk sac for food.
• Once the nutrients in the yolk sac are used up, the young halibut becomes a postlarva floating along the surface of the water and feeding on plankton. During this stage, the halibut’s fins and internal organs start to develop, and the left eye slowly moves over the top of the head to the right side of the fish.
• At about six months, the young halibut then settles at the bottom of the ocean in shallow inshore areas and feeds on small fish and shrimp-like organisms.
• Within a year or two of settlement, the juvenile halibut begins to counter-migrate (travel in the opposite direction to the currents that carried it as an egg or larva), and starts moving from nearshore areas to the continental shelf habitats.
• The counter-migration continues until the fish is large enough to be caught in the commercial fishery. Adult halibut migrate seasonally and long distances from the more shallow feeding grounds in the summer to the deeper spawning grounds in the winter. However, many adult Pacific halibut continue to migrate along the continental shelf, generally, though not entirely, eastward from the Bering Sea and Gulf of Alaska to northern California.
Source: International Pacific Halibut Commission
Decades of scientific studies have provided the Flat out Facts about the biology and life cycle of the wild Pacific halibut.