Specieswatch: glass eels – can these slippery customers stage a comeback?

Efforts to protect the European eel, under threat from pollution and the damming of rivers, are having some success

This is the peak season for the arrival of what is hoped will be millions of glass eels swimming up Britain's estuaries to reach fresh waters where they can grow into adults. The European eel (Anguilla anguilla) is a curious creature with a complex lifestyle that is still barely understood.

Eels are thought to begin life as eggs in the Sargasso Sea; drifting as larvae for about a year 4,000 miles north-east in the Gulf Stream before turning into tiny transparent eels. Their goal is to find a home in rivers, lakes and ponds while growing darker and larger for up to 10 years. When nearly a metre long they set off back across the Atlantic to breed.