Marine Biology

Life Cycle of American Eel

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The life cycle of the American Eel (Anguilla Rostrata) has a very complex life cycle and its body completely changes at different times of the eel’s life.  These changes are called metamorphoses.

The eggs of the American Eel are laid and fertilised in the Sargasso Sea.  These eggs hatch and turn into larvae.  These are juveniles are called glass eels as they are transparent.  The second stage the eels darken and go a grey colour and are then called elvers.  Slowly these develop into yellow eels reaching the fresh water streams or estuaries of the United States this could be as far as 6000 kilometres away from when they were just an egg.

During the yellow phase of the American Eel it is nocturnal and only moves and hunts at night eating fish, insects and dead animals that it finds.  An interesting fact is the American Eel can absorb oxygen through their skin as well as their gills.  This is a way that the eel can move across land to reach the next stream or water course.

When the eel reaches the fresh water streams it stays and grows the females can get up to 5 feet and the males up to 3 feet. They take a long time to mature it can take about 10 to 25 years.  It is during this time when they are able to cover their bodies in a layer of mucous making capturing difficult.

When the eel is sexually mature they will change again and travel back to the Sargasso Sea to lay eggs or to fertilise the eggs.  It is during the travel back to the sea when they become silver and the digestive system starts to degenerate, they don’t eat again on this journey this allows them the ability to travel in the sea.  Once the eel has reproduced, laid egg or sperm deposited on the eggs the eel will die.

The life history of the American Eel is not completely understood, why they need to travel back to the Sargasso Sea, the only place that eel will lay their eggs? How the eel knows where to go to lay the eggs, the rivers and sea will have changed how do they know the exact spot?

They are a fish species that has the greatest diversity and one that has survived from the ice age.  Yet now this species is seeking submission on to the endangered species list, why would an animal that has gone through so much be wiped out?  The American Eel needs understanding and research to make sure it survivors for the future generations.

More about this author: Sharon Rowe

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