Which large freshwater fish, once common in French rivers, can reach over 2 metres in length and has been the subject of intensive conservation efforts?

• A European eel
• B Wels catfish
• C Atlantic salmon
• D European sturgeon ✓

The European sturgeon (Acipenser sturio), the source of caviar from the Gironde, is critically endangered; the last wild population in France spawns in the Garonne-Dordogne basin.