Citizen Scientists help save the European eel

Some of the 2012 citizen science eel monitoring team
In October 2012 a gathering of these volunteer scientists marked the completion of the second successful year of this venture. Over 60 of the 162 eager eel volunteers visited London Zoo for an update on the project so far, with presentations from some of the leaders in eel research and management.

We are delighted that Kingston University, Northwest Kent Countryside Partnership,The Medway Valley Countryside Partnership, The London Wildlife Trust, Friends of River Crane Environment, Thames 21, Thames Anglers Conservancy, The Thames Rivers Restoration Trust and The Wandle Trust have already signed up to the scheme. Each team of volunteers monitors a specially designed trap, weighing and measuring the elvers before releasing them upstream. It is a testament to our recruits that they diligently monitor the traps come rain or shine, no eels or hundreds, throughout the entire six month migration period.

The European eel (Anguilla anguilla) has one of the most fascinating of all animal life-cycles. Beginning life as a leaf-shaped leptocephalus larvae in the Sargasso Sea, they make an incredible two year migration across the Atlantic Ocean to the rivers and shallow coastal waters of Europe. They enter European rivers as inter sex, elvers, spending between 12 and 30 years as adult ‘yellow eels’ before undergoing yet another metamorphosis where their eyes enlarge and their bellies change to a silver colour and they start the long swim back to breed then die in the Sargasso Sea.

Research over the last 30 years has shown all is not well with the European eel leading to its 2008 Critically Endangered (CE) classification in the International Union for Conservation of Nature’s (IUCN) Red List of Threatened Species. Recruitment of the European eel across Europe is believed to have declined by up to 95% since the 1980s. Reasons for its decline are muted as a combination of habitat loss, barriers to migration, presence of a parasite in its swim bladder, over-fishing, and climate change affecting oceanic currents.

Since spring 2005 ZSL has been monitoring upstream migration, capturing a picture of the juvenile eels entering the river (termed recruitment), providing the only data of its kind in the Thames catchment . We have found dramatic declines of up to 90% in seven years.

The information from this project allows us to better understand what action is needed to help conserve the eel by showing trends in population size, distribution and density. In 2011 and 2012, with the generous funding of Esmeé Fairbairn Foundation, we have been able to expand the number of sites in the monitoring programme by enlisting the Citizen Scientist's support. The results of the surveys will be used to shape the management of the Thames River Basin for the benefit of the endangered European eel.
We are still looking for help, so if your group of volunteers would be keen to ‘adopt’ a trap and check it twice per week during the elver migration, please get in touch with us at marineandfreshwater@zsl.org. Any collected data will be fed directly to a database on the ZSL website and you can find the 2012 report to the right of this page.