Helping eels along their incredible journey

Every eel you find in open water will have undergone an astounding 7,000km journey to get there – Ben Norrington from the Environment Agency is helping them on their way.

Several hundred metres down river from Flatford Mill is a mysterious sounding location called Judas Gap.

It’s an idyllic stretch of the River Stour save for a large concrete weir, which presents an intimidating obstacle for young elvers determined to make their way upstream and into the river system on the Suffolk/Essex border.

I’m here to meet Ben Norrington, a fisheries officer with the Environment Agency (EA), to learn more about the work he is doing to help these fascinating creatures – once plentiful in our waterways but now endangered.

He opens a white box on top of the weir and empties out several nets into a bucket of shallow water into which a total of four young eels, known as elvers, swim. They are tiny – no more than 6 or 7 centimetres in length – but full of vim and vigour.

Judas Gap


This is one of a number of monitoring stations the EA operates across the region that are used to measure eel numbers. Ben tells me the first elvers of this year started to appear in mid-April and that the most he recorded was several thousand in one 24-hour period in May.

These are all young eels who have undergone an incredible 7,000km, 300-day journey across the Atlantic after having been born in the Sargasso Sea – a sea within an ocean near Bermuda, and who are compelled to make their way up river into the fresh waters of Europe where they will live their lives for up to 70 years (although for many it’s much less), before making a return journey to spawn.

Ben demonstrates this in-built compulsion to swim against the flow by swirling the water in the bucket clockwise – almost immediately the elvers start to swim furiously anti-clockwise, revelling in their need to disobey logic.

Elver in Ben’s hand Image: Ross Bentley


As well as serving as a monitoring point, the tube into which the elvers swim also acts an ‘eel pass’. It is lined with broom like bristles that help the fish crawl up to the top of the weir and over into the freshwater on the other side. Ben tells me elvers are known for their clambering abilities and that they have been filmed climbing walls.

“Migrating is the eel’s biggest challenge and one of the biggest blights on their journey are the dams and weirs,” he said.

“They were put in decades ago to maintain water levels and to protect the land but we didn’t fully know the consequences of what were doing.”

Many of these constructions are impregnable to eels as well as other migrating fish such as trout, and across the country the EA has worked to make over 2,000 of these barriers passable.

Ben continues; “We’ve put in a lot of the linear fish passes and in the north there have been some incredible projects, where the concrete weirs have been broken up into boulders, so the water runs down like a cascade. It’s a longer, shallower descent – it’s still changing a head of water but its replicating nature.”

The reason this work is important is because the European eel is in dangerous decline – an EA report in 2009 stating that numbers across the continent had fallen by as much as 95% in the last 25 years. The fish, once unimaginably plentiful – sold by the barrel load by medieval fishermen in the Fens – is now classified as critically endangered on the IUCN Red List of Threatened Species.

“Every pond, lake and river would have had an eel in it,” said Ben. “They are incredibly adaptable and can live in low quality water – the silt in reservoirs, the village pond and someone’s drain.”

We still don’t fully understand the incredible journey of the European eel

Curiosity killed the eel

Adaptable, yes, but helpless, it would seem, in the face of the many man-made challenges that face them at every turn. While weirs and dams are believed to be a major cause of the decline, pollution, over-fishing, disease and climate change are also said to be having an impact,

The eel’s desire to explore nooks and crannies can also prove fatal in the modern age.

“Eels are renown for their curiosity,” continued Ben. “They follow flows of water and go into every inlet they can find – research found that eels were dying by swimming into the turbines of power stations and other industrial pipes. It’s now regulation that many of these inlets are screened.”

We agree that if Pixar is looking for a follow up to Finding Nemo, the journey of the eel would make a blockbuster.

Ben added: “You have the adult coming from a farm lake in Suffolk, cruising down the river and working how to get over locks and weirs in rainfall. Then they go out to sea, while avoiding the power stations, the fisherman nets, the predators, and then they have another 5,000 kilometres to get to the Sargasso – it’s an incredible journey.”

This article first appeared in the East Anglian Daily Times in July 2018

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