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Freshwater eels
11 January 2005
Young eels (called elvers) hatch from eggs in a deep part of the western Atlantic Ocean called the Sargasso sea.
The young eels migrate back across the Atlantic towards the coast of the UK, drifting in the warm waters of the Gulf Stream. This journey takes about two years. By the time they arrive they are about 5 cm long.
They gather in large river mouths like the Severn Estuary, and then head upriver in search of a new freshwater habitat. The urge to migrate is so strong that eels sometimes leave the water to wriggle their way overland.
The eels spend about 12 years inland, getting bigger all the time. Once the males are 36 cm and the females 46 cm long, they are mature enough to breed. In July, they return to the sea and begin the long journey back to their breeding grounds. When they reach the warm waters of the Sargasso sea, they lay their eggs and die. Any idea why they do this?