Epic journey of European eels

Posted on 2019-03-06 10:47:39

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Many animals have a clearly demonstrated homing instinct, often so strong that it seems almost beyond belief. This includes even domesticated animals. Pets like dogs and cats have often re-joined their owners when vast distances separated them.

A scientist called Johannes Schmidt made the discovery that apparently every eel in the western part of the world is born in the Sargasso Sea between the West Indies and the Azores. Trace this on a map to see how extraordinary this journey is. To find the Sargasso Sea on a map, move left from the Mediterranean towards the Bahamas.

Every autumn, eels leave their homes in rivers in Europe and on the east coast of America and make their way to the ocean. They then journey across the Atlantic to the Sargasso Sea where they will breed for the only time in their lives, and then die.

Tagging and the use of transmitters have revealed that the eels swim more than 4,800 kms to the Sargasso Sea. Their breeding processes have actually not been witnessed but it is clear that the adult eels spawn and lay eggs.

A female can lay up to four million buoyant eggs in the year before she dies. Eels live in fresh water and estuaries and leave only to go on this last incredible journey. They do not all go en masse, but appear to choose their own time to leave fresh water and often take convoluted routes. If European eels do not make it to the Sargasso Sea to spawn the following season, they simply wait until the next year to do their egg-laying, following some evolutionary pattern.

Two or three years after birth, the baby eels, known as elvers, drift across the ocean from the Sargasso Sea and go to the areas in which their mothers originally lived. They are still very tiny, only about five cms long.  Here is another extraordinary aspect: those baby eels that have 115 vertebrae head for Europe, and those with 107 vertebrae head westwards for America. There they will carry on with the cycle, since their parents will have died in the Sargasso Sea.



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