Biology & Lifecycle
Wild Pacific halibut are found along the continental shelf in the North Pacific Ocean and Bering Sea, and as far west as Japan and Russia.
Wild Pacific halibut are able to migrate great distances and have been caught as deep as 1,220 metres (4,000 feet).
Wild Pacific halibut spawn in deep water where females will lay between 500,000 to 4 million eggs depending on their size. For example, a female weighing 23 kilograms (50 pounds) will lay about 500,000 eggs while a female weighing over 113 kilograms (250 pounds) can produce about 4 million eggs. Nearly all halibut over 60 kilograms (100 pounds) are females.
Each fertilized halibut egg, or embryo that is about the size of a pea, 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 around the Northeast Pacific Ocean for about six months. During this stage, the larva uses 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.
The young halibut then eventually settles at the bottom of the ocean in shallow feeding areas. It is usually less than 30 centimetres (12 inches) long and feeds on small fish and shrimp-like organisms. After about two to three years, it migrates back to the deep, more southerly and easterly waters with fish becoming a more important part of its diet including cod, sablefish, pollock, rockfish, turbot, shrimp, squid, clams and crabs.
When it is about three years old, the halibut begins to counter-migrate (travel in the opposite direction to the currents that carried it as a larva). Scientists however still aren’t sure if it is travelling back to the place where its parents lived or if it’s guided by some other unknown factors. Most adult fish tend to remain on the same grounds every year, but migrate seasonally and long distances from the more shallow feeding grounds in the summer to the deeper spawning grounds in the winter. However, a measurable number of the adult halibut continue to migrate generally, though not entirely, eastward from the Bering Sea and Gulf of Alaska to northern California.
Female wild Pacific halibut are usually 10 to 12 years old when they spawn on the same grounds where they were hatched, and males are usually about eight when they reach sexual maturity.
While wild Pacific halibut are occasionally eaten by marine mammals, they are less vulnerable to predation than other species on account of their size, active nature, camouflaged bodies and bottom dwelling habits.