European eels face more than double the number of barriers as had previously been recorded when travelling along the River Mole and its tributary rivers, a pilot conservation project has found.
Volunteers trained by the South East Rivers Trust (SERT) as part of the Thames Catchment Community Eels Project found 119 impediments – such as weirs, sluices and culverts – 66 of which were new to existing data.
SERT also held workshops and assemblies for 1,136 children, 106 people heard their talks about the lifecycle of eels and 148 took part in guided walks. In addition we trained 31 volunteers to monitor eel numbers at the Island Barn sluice in Molesey, where they recorded about 2000 passing through the eel pass.
The 23 citizen scientists trained by SERT assessed 107km (66.5 miles) of the River Mole network. This stretches from Crawley via Horley along the Mole Valley to East Molesey and Thames Ditton, where it joins the River Thames.
The critically endangered European eel, a species of fish, starts life hatching out of a tiny egg in the Sargasso Sea, in the Atlantic Ocean, before travelling 6,500km to Britain.
Eels spend most of their lives in Britain’s freshwater rivers. They need to be able to travel around river networks so that, after many years as fully grown adults, they can eventually make the immense journey back to the Sargasso Sea to spawn.
However, their journey along many rivers is inhibited by a range of man-made obstacles.
The Thames Catchment Community Eels Project is a partnership led by Thames Rivers Trust and working with Action for the River Kennet (ARK), South East Rivers Trust and London-based environment charity Thames21.
The project works closely with the Zoological Society of London (ZSL) and Thames Estuary Partnership (TEP) to aid the long-term survival of the European eel.
Polly Penn, Head of Working with Communities at the South East Rivers Trust, said: “We have been excited to be part of this project.
“It was a great opportunity to teach people about the lifecycle and plight of the European eel, as well as to contribute to vital data showing the barriers they face in moving along our rivers.
“The South East Rivers Trust has lots of experience either removing barriers or creating fish passes and we hope this project will lead to further enhancing nature along the River Mole in this way.”
Dave Wardle, Chairman of the Thames Rivers Trust, said: “The European eel is an iconic fish and plays an important role in the ecosystems of the Thames and its tributaries.
“We are very pleased to have been able to give local communities along five rivers in the Thames catchment a range of opportunities to discover more about their rivers, eels and their local Rivers Trust.
“The next step is to secure funding for barrier removal or eel passes at the priority sites for eel passage identified during this project.”
The various partners trained 97 people to assess the passability of barriers, using a new methodology called ObstacEELS.
In total, the partners trained 97 people, who found 457 barriers, 278 of which were previously unrecorded in data systems.
This work took place across five river systems – the Pang, Upper Brent, Mole, Ravensbourne and Middle and Lower Kennet.
In total, 2,500 children learned about eels through workshops and 680 people of all ages took part in riverbank eel walks or attended talks.
The Thames Catchment Community Eels Project is funded by the government’s Green Recovery Challenge Fund, which is delivered by The National Lottery Heritage Fund in partnership with Natural England and the Environment Agency.
The new data on eel barriers has fed into the Environment Agency’s Thames Basin Eel Management Plan and Thames Estuary Partnership’s Fish Migration Roadmap, where the findings are freely available.
The data will be used to inform future action plans across the Thames Basin to possibly remove the barriers or find ways around them such as installing fish passes.