Interesting facts about the European eel

  • How many species of eel are there?

    There are about 800 species of eel in the world and two in the UK, Conger and European.

  • How long have eels been around for?

    Eels have been around for about 50 million years!  The European eel is Critically Endangered – you can find more information on the International Union for Conservation of Nature’s (IUCN) Red List of Threatened Species.

  • Eels are a part of the Thames cultural heritage

    Every year young eels known as elvers arrive from the Sargasso Sea and swim up the Thames, however that journey is hindered by the many barriers on the river.

  • Jellied eels

    Eels were once an important nutritious and readily available food source for the working class of London.

Jellied eels
  • How many eggs does an eel lay?

    A female eel will lay between 1 and 4 million eggs! She will only spawn once in her life time and this is called semelparous.

  • Did you know that eels are crepuscular?

    European eels are crepuscular. This means that they are most active at dawn and dusk. There are of course exceptions, so this doesn’t apply to all of them and not all of the time.

  • Did you know that eels are catadromous?

    Catadromous is the name given to fish that start their life in the salty waters of seas and oceans,  migrate to freshwater for part of their life cycle and return to the sea to breed. The European eel does exactly this, hatching from a tiny egg in the Sargasso Sea, then migrating to our rivers and finally setting off and fully maturing into an adult eel on the journey back to the Sargasso Sea; where it will breed just once in its lifetime.

  • When do eels become male or female?

    Eels do not have a sex until later on in development, when they are about 30cm long. What sex the eel becomes is determined by density of eels in the river or estuary (not all eels make the journey up the river, some will spend years in the Thames Estuary before migrating back to the Sargasso Sea) – lower species density equals more females.

  • Eels can travel across land

    Eels can leave water and travel across damp grass, but have no sense of direction when they leave water.

  • Final life cycle stage of an eel

    When the eel develops into its final life cycle stage, the eel’s body adapts to become a silver eel and no longer eats, instead living off of their fat reserves.  The downstream migration of seabound Silver eels happens in the autumn. These changes are to cope with the salt water during the migration back to the Sargasso Sea. The Silver eel only becomes fully mature during the journey to the Sargasso Sea.

  • An eels slimy exterior

    Eels have a mucous coat, this slimy exterior gives protection from disease, deters predators and allows the eel to squeeze into tight spaces.

The 1086 Domesday Book records eels used as currency, to pay rent and taxes

The payment of rent and taxes in this way continued for another 500 years. This shows there used to be plenty of eels. Records in the Domesday Book show there were at least 56 locations where rents were paid in eels in the Thames catchment.

Interesting facts about the Thames catchment

  • The Thames is the longest river entirely in England

    The Thames rises at Thames Head in Gloucestershire and meanders 346kms where it eventually flows into the North Sea, via the Thames Estuary.

  • The Thames meanders through The Cotswolds Water Park, an area with 180 lakes

    The wetland landscape supported thousands of breeding waterfowl. The site is home to bats, water voles and otters.

  • Famous for its thousands of Snake’s head fritillaries, which bloom in April

    Meadows like North Meadow National Nature Reserve (NNR) were once common along the upper Thames.

  • Radcot Bridge is the oldest surviving bridge across the Thames

    It was was the scene of a battle on 19th December 1387 between the forces of Richard II and Henry Bollingbroke, the future Henry IV. This battle raged along the Thames to Newbridge and finished at Bablock Hythe.

  • The highest lock on the Thames is St John’s Bridge

    It’s a two-section road bridge across the channel of the upper Thames near Lechlade. This current bridge was built in 1886.

  • The Oxford stretch of the Thames is often referred to as the River Isis

    It was thought its original name Tamesis was a combination of Thame and Isis, this has turned out to be false. The name Isis has been used from its source in the Cotswolds until it is joined by the Thame at Dorchester in Oxfordshire.

  • The famous film The Eagle has Landed was filmed in 1976 partly at Mapledurham Mill

    A mill was already present at Mapledurham at the time of the Domesday Book – a medieval survey completed in 1086.

  • The River Kennet enters the Thames at Reading

    The Thames has 38 main tributaries feeding it between its source and Teddington. The Kennet is the largest. These tributaries contain a range of important habitats that support many species of wildlife, including water voles and otters.

  • Just above Henley bridge in Henley-on-Thames is the headquarters of the Henley Royal Regatta

    Below the bridge is the Leander Club, the most famous and successful rowing club in the world.

  • A salmon ladder was opened at Boulters Weir on 19 May 2000 by the Duke of Wellington

    The last salmon caught before the salmon ladder at the weir was landed in 192. This was one of 20 ladders installed through funding from Thames Salmon Trust, now know as Thames Rivers Trust.

  • Windsor Castle was the main residence for Queen Victoria and Prince Albert

    After Albert’s death the queen was sometimes called the ‘Widow of Windsor’. The castle is the largest inhabited castle in the world.

  • In 1215 King John signed the Magna Carta in a water meadow at Runnymede

    The exact location is unknown. This document limited the power of the monarch and gave legal rights to all. Nobody knows why a water meadow and Thames flood plain was chosen.

  • When King Henry VIII left Hampton Court he often used the river Thames to get up to London

    Henry would travel in the royal barge. Built during Tudor times and given to Henry VIII by Cardinal Wolesey, this impressive palace overlooks the north bank of the Thames.

Thames Catchment Community Eels Project completed in March 2022,  for more information please contact us

Working together in partnership

Thames Rivers Trust
Action For The River Kennet
South East Rivers Trust
Thames 21
Thames Estuary Partnership
Green Recovery Fund Project
The Thames Catchment Community Eels Project is funded by the government’s Green Recovery Challenge Fund. The fund is being delivered by the National Lottery Heritage Fund in partnership with the Environment Agency and Natural England.

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