Blog: Pareto engineer sizes up Cockney eels

Volunteering with Estuaries and Wetlands elver monitoring programme

To monitor the number of elvers (juvenile eels) swimming into Thames from the ocean, ZSL and collaborating organisations have set up eel traps, which are checked twice a week between April and September. The European eel is a critically endangered species, so collecting information on how they use our rivers and in what numbers they are doing so, is vital!

ZSL’s Estuaries & Wetlands team monitor two traps in North East London. Throughout the survey season volunteers from other ZSL teams and our partners come out to help us. It’s a wonderful opportunity to get a closer look at the Cockney eels; and learn a thing or two about their important place in the ecosystem.

[Not a bad day to go out to check on the eels! Henriette Hultmann and Ian McCloud all kitted up for wading the river]

On Friday the 13th we were lucky enough to have Ian McCloud, from Pareto’s engineering team at ZSL, accompany us to both survey sites. More apt for the survey date, there were unfortunately no eels at our first site, due to a malfunction in the trap’s waterflow. Ian was a great help in re-siphoning the pipe, again allowing waterflow down the eel-“ladder” leading from the river to the trap, as this is essential for the eels to be able to climb up and into it.

[Ian McCloud using small hand-nets to fish out the eels from the trap so that they can be measured, while Henriette Hultmann supervises.]

We had better luck at our second site where some eels had found their way to our trap! Here Ian got to try his hand at catching the eels, who are surprisingly quick for their size, as well as measuring them. After the measuring was done the eels were released upstream so that they could continue their migration further into freshwater, where they will spend the next 15-20 years of their life.

[All elvers are measured and ready to return to the river!]

Blog written by Henriette Hultmann of ZSL