Halibut spawn annually between November and March in deep water (600 to 1800 ft) near the edge of the continental shelf from British Columbia to the Bering Sea. The free floating eggs hatch after two to three weeks and as the larvae develop they gradually float upwards and drift in a northwest direction with the ocean currents. The larvae float for up to six months and drift 100’s of miles. During this free floating stage a major anatomical change takes place as the left eye migrates to the right side and they become a flat swimming fish.
After months of drifting the infant halibut are deposited in shallow coastal waters along the western Gulf of Alaska from Kodiak to the Bering Sea. These waters are rich with nutrients and the halibut will spend from 3 to 7 years feeding in these “nurseries” before beginning to migrate back in a clockwise or southeast direction compensating for the northwest larvae drift. Although most of the juvenile halibut which will spend the rest of their lives in Southeast Alaska complete this migration by the time they are 8 years old, “adult” halibut ranging 8 to 18 years continue to migrate from the western to the eastern Gulf of Alaska at the rate of about 6% per year. Halibut are highly migratory and will travel for 100’s of miles. According to IPHC reports, halibut tagged in the Bering Sea have been caught 2,000 miles away off the coast of Oregon.
Most female halibut are sexually mature at about 10 to 12 years and males mature at about 7 or 8 years of age. Once mature, halibut migrate seasonally between the offshore, deep water spawning beds and near shore summer feeding grounds. The halibut will move into shallow waters in the summer feeding on schools of cod, herring, salmon and anything else they can fit in their mouth. The summer migration and subsequent feeding frenzy provides an excellent opportunity for sportsmen to hook up with these prized fish.
Around September or October, halibut will begin their migration back out to deep water to spawn. Most spawning activity occurs between December and February.
Halibut can live to be very old reaching ages of 50 years, however few live past 30. Males are much smaller than the females and rarely grow over 100 lbs. Halibut are the largest of all flatfish and the official Alaska sport caught record is 459 lbs caught near Dutch Harbor in 1996. According to ADF&G reports, the largest halibut officially recorded In Alaska was 495 lbs taken near Petersburg. There are old pictures of halibut however, that are said to be over 900 lbs.