Eel Meet Again

To mark World Fish Migration Day on 21st April, ZSL's Joe Pecorelli updates on our European eel conservation. 

The month of April is a bit of a highlight for me in my work as a conservation project manager here at ZSL. As the Thames warms up a new cohort of European eel start migrating upstream through the estuary and into the tributaries and our most extensive citizen science project in the region, the eel monitoring, cranks up once again. Restarting the monitoring provides me with an opportunity to catch up with our loyal eel monitoring volunteers some of whom have been with us since 2011 when we started inviting volunteers to help with the project.  

Volunteers at the 2017 ZSL Eel Forum
Volunteers at the 2017 ZSL Eel Forum

We couldn’t do it without our citizen science volunteers!

What the volunteers do for ZSL is give us vital data on the eel migration by regularly checking our monitoring sites, counting, measuring and releasing any eels present and then uploading the data to our database.

Measuring eels is certainly not for everyone but we are blessed and grateful to have a remarkably dedicated core group of volunteers who, along with the new people that join the project every year, make up the 120 strong, elite eel monitoring team each season. In addition to the data collection the volunteers also add a community engagement and education dimension to our eel conservation work in the Thames region which makes the project especially attractive to funders.

Pioneering eel
Pioneering eel – the first eel caught in 2015 using the ZSL built eel pass that helps re-establish a migratory pathway between the River Thames to the River Crane catchment in west London


This has greatly helped us secure funding to build eel passes. These passes allow the eels to move upstream over the weirs and sluices that would otherwise block their movement. Since 2005 we have built passes that have improved connectivity to 138.79 km of river in the region and this year the work is set to continue with new passes planned for the River Cray, Mole and Roding. The simple idea is that the more habitat we open up by building passes the greater the numbers are of Critically Endangered eels that can grow and mature in our rivers before heading back to the Sargasso Sea to spawn. My Thames colleagues and I always have a little celebration, generally in the form of extra chocolaty biscuits in our team meetings (budgets are tight in conservation), when we install a new pass and record eels entering a section of river that would have formerly been inaccessible to them.

ZSL eel pass
Unphotogenic but effective for eels trying to get over weirs- the latest ZSL eel pass (black tube attached to the brick wall) built in 2017 on the River Roding


World Fish Migration Day

On April 21st we might well crack open the chocolate biscuits again to mark World Fish Migration Day, the international event that focuses attention on the need to accommodate the migration of fish through global waterways. Many migratory fish species around the world are severely threatened and society’s historic and continued building of impassable structures in rivers is a huge contributory factor to their decline. The rivers of the Thames region alone are bisected by over 2000 barriers so a monumental challenge lies ahead to remove or allow fish passage over all of them. 

You can help in this challenge by becoming a citizen science volunteer with us and by spreading the important message of World Fish Migration Day

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