Unknown risk of extinction
Also molluscs and other small invertebrates that live in the mud
Some species travel to the ocean
Also Asia and North America
Sturgeons are a highly valuable group of species – beluga sturgeon caviar (also known as black pearls) can fetch up to US$10,000 per kilogram.
This has led to over-harvesting of many sturgeon species. With sturgeon stocks depleted, fishermen are now turning to the closely-related paddlefish to meet the caviar demand.