By Cecilia C. Vargas, PhD*
This species, despite its long production time of about 5 years, has shown itself to be profitable. This is due to its good taste and limited availability. Atlantic halibut has high market attractiveness and it is considered a gourmet species, with high prices of approximately US$15 per kg (whole fish). Indeed, farmed Atlantic halibut from the Norwegian company, Marine Harvest - Sterling halibut - has won awards as a gourmet fish in both 2007 and 2010 at the prestigious Bocuse d’Or.
Attempts to culture Atlantic halibut date back to the mid-1980s, but it was not before the late 1990s that significant commercial production was achieved. Norway is the world’s largest producer of Atlantic halibut with a total of approximately 1850 tons reported in 2013. The biggest producers in Norway are Marine Harvest – Sterling Halibut, Nordic Seafarm and Aga Halibut.
Availability of good quality larvae is still the main bottleneck in the culture of this species. Atlantic halibut is a batch spawner and reproduction occurs during the winter months. Thus, accessing gametes of high quality obtained during the peak of spawning season is crucial. Broodfish are stripped for gamete collection and then gametes are mixed allowing fertilization. Optimal temperatures for egg incubation is approximately 6°C. Eggs are incubated in darkness in cylinders for two weeks. After hatching, larvae are transferred to larger cylinders, and kept in darkness for an additional 30-40 days until they have completed absorption of their yolk-sac.
The larvae are fed on enriched Artemia until around 70 days post hatching when they are weaned onto a dry feed. Start-feeding is a critical period where high mortalities are common and this is still the major bottleneck in juvenile production. At this stage, larvae go through metamorphosis where they become fry, the left eye migrates to the right eye and the fry seek the bottom of the tank. From 2g, larvae can be transferred to shallow tanks with shelfs creating more areal surface.
The grow-out phase begins from this size onwards, where the fish continue to be reared in shallow tanks fed with commercial diets. Further growth until the fish are transferred to sea cages varies between the producers. For example, Marine Harvest – Sterling Halibut culture the halibut in land based indoor tanks until they reach 300 g, following transfer to outdoor tanks until a weight of 1.5kg. Then, halibut are reared in 24x24m steel sea cages with 30m deep net pens until fish reach the market size of 5-7 kg.
Atlantic halibut is a species with sexual dimorphism in growth, where females grow larger than males. Under farming conditions, males mature around 2kg, long before market size and experiencing a deceleration in growth. On the other hand, females attain sexual maturation at a much larger size (12 kg), and reach market size before males. Therefore, the production of all-female halibut is more valuable than mixed sex culture. Norway is currently importing all-female halibut from Scotian Halibut in Canada.
Dr. Cecilia Campos Vargas recently earned her PhD at the University of Nordland, and works at Helgeland Havbruksstasjon, in Norway. She has many years of experience in production of live feeds and aquatic species like rainbow trout, Atlantic salmon, cod, and many Japanese species.