European eel conservation

ZSL thames eel survey

With the vital help of citizen scientists and partner organisations ZSL has been working for the survival of Critically Endangered European eels.

Volunteer as a citizen scientist

ZSL’s work for the European eel in the Thames

European eels (Anguilla anguilla) once thrived in London’s rivers but the number of young joining the adult populations have dropped by over 95% since the 1980s and the species has been classified as ‘Critically Endangered’ by the IUCN Red List of Threatened Species since 2008. ZSL’s work on European eels started in 2005, and it now ranges from informing international conservation policy, leading UK research on eel behaviour to regional-scale best practice conservation delivery in the Thames Catchment. Here we work in partnership with the Environment Agency to address the key conservation issues and improve the condition of the European eel populations in the Thames. We do this through research, river improvements, public engagement and advising policy.

How can you help?

One of the major threats to eels in freshwater are barriers to upstream migration such as weirs and sluice gates that reduce the amount of habitat available for eels to grow and mature. By volunteering as a citizen scientist to monitor the upstream eel migration at sites across the region you can enable ZSL and partnership organisations to better understand which barriers are disrupting migration so that we can install eel passes on them. By working in partnership with over 20 organisations the elver monitoring project has become the biggest in a single catchment in the UK.

Volunteer as a citizen scientist

Opening up migratory pathways

ZSL is a national centre of excellence for assessing the passability of river structures to eel. We have produced a number of barrier reports in the region and started a programme of eel pass building in 2013.  So far, we have installed 10 passes that have made an additional 35ha of river habitat accessible to eel.

Thames Eel Management Plan 

ZSL is a key partner in the Environment Agency’s eel management plan for the Thames region. The management plan outlines key targets and measures to improve the population and conservation of the European eel.

Using technology for research 

ZSL’s eel research in the Thames includes tagging studies to investigate eel populations in marshlands that line the lower estuary. The study, now complete, showed the significance of these habitats for eels. 

ZSL also recently worked with the Environment Agency to trial the use of innovative new technology for monitoring downstream migrations of mature European eels. Using ARIS - Adaptive Resolution Imaging Sonar, to record videos of eels, we helped demonstrate how this technology can provide new insights and valuable information on the numbers of eels leaving Thames tributaries on their migration to the Sargasso Sea.

Project Information

Key species:

  • European eel (Anguilla anguilla)

People Involved:

  • Joe Pecorelli, Anna Saltmarsh and Clara Obregon work on the European eel conservation project.
  • Joe Pecorelli leads the Citizen Science Eel Programme.

Partners and Sponsors:

  • Environment Agency

Kindly funded by:

  • The City Bridge Trust
  • Environment Agency
  • D’oyly Carte Charitable Trust
  • Panton Trust




Eel Animation

Find out about the incredible life cycle of the Critically Endangered European eel and their amazing migration.