There are around 15 species of eels in the Anguillidae family, all of them long, snake-shaped fish and most of them migrating between the ocean and freshwaters inland during different parts of their lives.
The most remarkable journey is made by the European eel, (Anguilla anguillla). Born in the Sargasso Sea, in the central Atlantic, they hatch into transparent larvae that look like leaves with tiny fish heads stuck on. They drift for thousands of miles on Atlantic currents and arrive on the shores of eastern Europe where they transform into bootlace-sized young, known as glass eels or elvers.
They mature in shallow coastal seas and eventually change colour to become larger yellow eels before migrating along rivers and into lakes. For decades, eels stay in inland freshwaters, before changing colour again to become metre-long silver eels.
Silver eels are the final life stage and have the intrepid task of retracing their paths from decades earlier, and swimming all the way back to the Sargasso Sea. It’s only when they approach the spawning waters that males and females mature and their sexual organs develop.
For years, the epic life cycle of European eels remained an unproven theory. It was only in 2022 that scientists tracked silver eels to their spawning grounds, where the females release millions of eggs that are externally fertilised by the male eels.
The next big question is what the future will hold for eels. The number of glass eels arriving at European coasts has plummeted by more than 95 per cent in recent years, and the species is highly endangered. They face many problems, including dams blocking their migration routes and illegal trading of glass eels to rear in fish farms.
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