status: Critically endangered, IUCN
range: Albania, Algeria, Atlantic Ocean, Belgium, Black Sea, Estonia, Finland, France, Georgia, Germany, Greece, Hungary, Ireland, Italy, Mediterranean Sea, Morocco, Netherlands, Norway, Poland, Portugal, Romania, Russia, Serbia and Montenegro, Spain, Sweden, Switzerland, Turkey, Ukraine, United Kingdom
Description and biology
The Baltic sturgeon is a large, slow-moving fish that may grow to a length of almost 10 feet (3 meters) and weigh up to 440 pounds (200 kilograms). It has a shovel-shaped snout with four fleshy barbels (slender feelers) extending outward from between the tip of its snout and its mouth. Five rows of bony plates line its body.
Young Baltic sturgeons feed mainly on insect larvae, mollusks, and small fish, while adults eat small fish, worms, snails, and crustaceans such as crayfish. These sturgeons probe the bottom mud and sand of their water habitat in search of food. Their sensitive barbels detect prey, which they then pick up with their protruding lips.
Adult sturgeons spend most of their lives at sea. In early spring of each year, they enter the mouths of connected rivers
to spawn (lay eggs). These rivers are swift-flowing, have gravel bottoms, and are 20 to 26 feet (6 to 8 meters) deep. After a female releases her eggs and a male fertilizes them with sperm, both return immediately to the sea. After hatching, the young sturgeons remain in the river or its estuary (lower area where it flows into the sea) for two to three years. Baltic sturgeons grow more rapidly than other sturgeons.
Habitat and current distribution
Baltic sturgeons are currently found only in scattered portions of their former range. The largest population now occupies the Black Sea. In the early 1980s, biologists (people who study living organisms) estimated that population numbered no more than 1,000. They now believe that number has dropped significantly.
In order to spawn, the sturgeons need deep, fast-flowing rivers.
History and conservation measures
Baltic sturgeons were once widespread in the northeastern Atlantic Ocean and in the Mediterranean, Baltic, and Black Seas. They were occasionally caught around Ireland or off the coasts of northern African countries. By the 1970s, only single sturgeons were seen or caught in the Rhine, Po, Gironde, Danube, and Douro Rivers.
While overfishing has been a problem, this fish has declined in number mainly because its spawning grounds have been damaged. In some cases, breeding rivers have been altered, such as widened or deepened, to make them more navigable for ships. In others, locks and dams have been built on rivers, preventing the sturgeons from reaching spawning grounds. Many of the rivers in the Baltic sturgeon's range are now polluted.
The Baltic sturgeon is on the endangered species lists of France, Poland, Germany, and some countries of the former Soviet Union. In France, efforts are underway to develop a captive-breeding population to produce caviar (the eggs of the sturgeon eaten as a delicacy). Conservationists (people protecting the natural world) hope this captive-breeding population will also be used to repopulate rivers in which the Baltic sturgeon formerly spawned.