Monday, 28 December 2015

The once Common Eel is now Critically Endangered

The European Eel is no longer common

The European Eel (Anguilla anguilla)  used to be known as the Common Eel, and when I was a boy this was an apt name, however, this is no longer the case because this species of eel is now listed as Critically Endangered. In 2010, Greenpeace International added this fish to its red list. 

European Eel (Photo: Public Domain)

European Eels have a most unusual lifecycle. The adults spawn in the Sargasso Sea and the baby eels travel across the oceans to return to fresh waters far far away. How they navigate is not understood. They drift as larval eels for around 300 days before transforming into a stage known as "glass eels," which occurs when they approach the coasts.  Eventually they enter estuaries in the UK and Europe and transform again into elvers in the fresh water. The eels travel upstream and will also travel overland in storms. They live in rivers, streams, lakes, and ponds where they grow much larger and are known as "yellow eels," but after between five and twenty years or more they become adults that must return to the sea. The final stage is known as the "silver eel," and these eels swim all the way back to the Sargasso Sea where they breed and then die.

When I was younger the European Eel used to be one of the most easily found freshwater fish. You just had to go to any river or stream and turn over a few stones and you would be likely to see young eels or elvers.  In Cardiff, where I lived, there is a weir in Llandaff, and every year countless thousands of elvers used to try and ascend it. To do this they would leave the water at the edge of the weir and slither up the mossy wet rocks and wall.  If you put a bucket or net underneath and disturbed the mass of young eels at the top you would quickly get a net or bucket full of them. That was how easy they were to catch. Nearly every rock in the river would have elvers hiding underneath it or larger eels.  That was then but it is a very different story today, so what has happened? 

One of many endangered species

Like so many once common species, the European Eel is now rarely seen in Britain today and its numbers have dropped very dramatically.  Since the 1970s, it has been estimated that eels reaching Europe have declined in numbers by over 90%, possibly as much as 98%. This is surely a warning sign that all is not at all well, when it comes to the natural world and the flora and fauna of the UK.

So what has gone so wrong and where have all the eels gone?  The reasons are many and include: overfishing, hydroelectric dams and barrages blocking the way for the eels to ascend and descend rivers,  parasites, pollution and changes in the currents in the oceans. Whatever the cause may be, the eels have gone, and with them has gone the food source for many species of water birds, including Kingfishers, predatory fish, like the Pike, and even some mammals too, such as the Otter.  The eel is an important part of a food-chain, and without it other species are sure to suffer.  

Saving the European Eel

Fortunately all hope is not yet lost for the future survival of the European Eel. Fish passes are being increasingly installed in rivers with weirs and dams, so that eels and other fish, such as salmon, are able to get upstream.  

The number of eels is being monitored and there are projects in operation to save the European Eel. Restocking inland waters with young eels is one method that is being put into practise. 

The Guardian has reported that conservationists have suggested that the decline in numbers of the species has been halted and possibly reversed.  I hope this is true but it is far too early to know for sure! 

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