top of page


Updated: Oct 7, 2021

The Thames Eels! What do you know about these creatures, their lifecycle and the challenges they face? Find out all b-eel-ow and see how many more eel puns we can get in.

The European Eel (Anguilla anguilla), once common, are currently classified as Critically Endangered in the IUCN red list of threatened species. You can find out more r-eely interesting facts about the European Eel here, including that one female eel will lay up to 4 million eggs!

We are thrilled to be a part of the Thames Catchment Community Eels Project which strives for the long-term survival of these eels. The project is led by the Thames Rivers Trust in partnership with the Rivers Trusts Action for the River Kennet, South East Rivers Trust and Thames21, and in collaboration with ZSL. This 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 Natural England and the Environment Agency. This project spans several river catchments, including the Brent and Ravensbourne and is running between December 2020 and March 2022.

Eel Life Cycle

The European eels hatch from tiny eggs in the Sargasso Sea, in the northwest Atlantic. After hatching, they then develop into larvae called leptocephali (about 5mm long), and by utilising the currents in the North Atlantic, they float towards Europe. This journey can take up to 2 years covering over 6,500km in distance.

The leptocephali larvae gradually grow during this migration and by the time they reach the continental shelf of Europe, they have metamorphosed into glass eels. The glass eels or elvers then move into estuaries and freshwater rivers across Europe, including our beloved Thames Estuary, the River Thames, and its tributaries. Here, they find suitable habitats and food to grow and develop into yellow eels.

After spending 5–20 years in freshwater, the yellow eels become sexually mature, their eyes grow larger, their flanks become silver, and their bellies turn white – at this stage, they are known as silver eels.

The silver eels then begin their 6,500 km long migration back to the Sargasso Sea where they spawn and then die.

You can watch the life cycle on YouTube below.

TEP’s Part

Following the success of the Fish Migration Roadmap Project, we are collaborating on this project to map artificial barriers like locks, sluices and weirs, that inhibit the eel’s ab-eel-ity to migrate through the Thames River Basin. Barrier data collected by trained ObstacEELS volunteers will be incorporated into the Fish Migration Roadmap and the Thames Basin Eel Management Plan (EMP) to investigate what needs to be improved or altered for the eels to successfully migrate throughout their lifecycles.

Get Involved

There are many ways to get involved in this project and the different aspects, including in schools and by volunteering, including Citizen Science work on the following rivers:

· Middle & Lower Kennet

· Mole

· Pang

· Ravensbourne

· Upper Brent

Please find more information about Citizen Science and how to get in touch here.

There are also lots of Educational Resources, including eel anatomy sheets and colouring activities, to teach and learn at home and school. These are available here.

There are also many other upcoming events for this project, including guided walks and talks, you can find out more here.

You can also now listen to our brand new Talk of the Thames podcast, in which we talk to the wonderful people involved in this project!


bottom of page