The paddlefishes and sturgeons group is a small order of fish that includes about 25 species in two families. This is an ancient fish lineage, dating to before the age of the dinosaurs. There are two species of paddlefish, one in North America and the other in China. There are about 23 species of sturgeons. Sturgeon species can grow to be huge, 4.2 meters (14 feet) or longer and up to 2000 kilograms in mass. Beluga sturgeon are the largest freshwater fish in the world. These are also long-lived fish, living 120 years or more. However, sturgeons have been widely and intensively used by humans for both meat and their roe (eggs), which is made into caviar. As a result most sturgeon species are at risk of extinction.
Tanya Dewey (author), Animal Diversity Web.