Largest flatfish

The world's largest species of flatfish (i.e., fishes belonging to the taxonomic order Pleuronectiformes) is the Atlantic halibut (Hippoglossus hippoglossus). Native to the North Atlantic from as far north as Labrador (Canada) and Greenland to as far south as the Bay of Biscay and Virginia (USA), it measures up to 4.7 m (15 ft 5 in) long, and adult females (much larger than adult males) can attain a weight of as much as 320 kg (705 lb 8 oz), during a lifespan of up to 50 years. However, their size is determined less by age and more by the abundance of available food – the greater the abundance, the larger the halibuts grow.

Taxonomically speaking, there are only three species of flatfish that are true halibuts – the other two are the Pacific halibut (H. stenolepis), and the Greenland halibut (Reinhardius hippoglossoides). The Pacific species is only slightly shorter and slimmer than the Atlantic, but the Greenland species is much smaller. However, there are also various less closely related flatfish species that are loosely referred to as halibuts, such as the spotted halibut (Verasper variegatus) of the north-west Pacific.