Can you imagine swimming 4000 miles? In rough seas. Crossing two continents. And you’re only the size of a pea…
No, neither can we! But that’s exactly what the unassuming European eel does. Spawning in the Sargasso Sea, these wriggly beauties form in tiny spherical eggs deep in a western section of the Atlantic Ocean. Hatching into larvae called leptocephali, they look nothing like a typical image of a snake-like sea creature, but instead have the appearance of a see-through leaf.
Over the next one to two years these opaque creatures give themselves to the current of the oceans and drift over 4000 miles to the continental shelf of Europe. But they aren’t lazily enjoying the views during this time. Instead they are busy transforming. Their leaf-like shape flattens and elongates as they enter into their ‘glass eel’ stage of life.
Upon reaching our English coastline they use the force of the tides, and their new found body shape (around 8 cm in size now), to push themselves upstream to make a home in our rivers. Switching from sea to freshwater brings on another amazing transformation - a colour change this time. The eels start to pigment. Like gangly teenagers, now 12 cm in size, trying out a new look, they turn brown marking the start of the ‘elver’ stage, their adolescent era.
You’d think that would be enough transforming for one squirmy being but the European eel is only just getting started. Once embedded in their new freshwater habitat they grow up to 1 metre in length, now looking much more like our usual depiction of an eel. This is their ‘yellow eel’ phase - their immature adult phase which, like some humans, they remain in for somewhere between 5 and 20 years, depending on food, sex and temperature.
And now for the fantastical finale. A masterful metamorphosis and another gigantic journey. Once the eels have lived a peaceful life in our beautiful rivers, gorging on fish, molluscs and crustaceans - oh and not forgetting the odd slug or snail… did we not mention that they can also leave the water and cross dry land should the urge take them… Just another string to this amazing creature’s bow! Upon reaching adequate size and with satisfying fat supplies accumulated, the eels enter their final stage, the fully matured ‘silver eel’ stage.
Another colour change, this time to a gracefully aging grey, their pectoral fins widen and muscle mass increases, their digestive tract shuts down and their eyes grow up to ten times their original size, all to help see them through their final swim. Fighting their way back against the strong currents, the silver eels head for home, where it all began. Another 4000 mile long journey to the Sargasso Sea to spawn and end their days in warmer climes.
So we think you’ll agree, the humble European Eel has an epic life cycle. Just one more fact for you. Even when their eyes have grown ten times their original size, their eyesight is terrible. But to make up for it they have four nostrils giving them an amazing sense of smell, which clearly helps them find their way home!