Once upon a time, sturgeon the size of school buses roamed the oceans, seas, and rivers of the world. Huso huso is the largest and now the rarest species of sturgeon, growing on average to about 25 feet long. Huso huso lives in the Caspian and Black Seas and it is now unclear whether the species has gone extinct in the wild or not. When the International Union for Conservation of Nature (the IUCN) last surveyed the species in 2010, the population had decreased by 90% over the past sixty years and a number of the populations had gone extinct in the wild. Most if not all individuals are now bred and raised in hatcheries.