Counting East London’s eels as they ebb from the River Lea

John Bryden from charity Thames21.

Not so long ago eels were ubiquitous. Vast numbers drifted from the wide Sargasso Sea, lapped around our shores and into our waterways where they were caught in baited baskets, sold to pie and mash shops, chopped up and served to cockney geezers as the archetypal East End dish.

A fenland town, Ely, was so synonymous with eels (so eely) that it was named after them.

Ask older relatives from London to reminisce and they may remember eels. I saw my first, a large adult, all muscle, in an upriver Thames tributary when I was about six. My uncle once bought a live one home from a street market and kept it in a fish tank before releasing the disorientated fish into the River Brent.

Now eels have gone the way of cockneys. They are officially classified as “critically endangered”. What few pie and mash shops survive now source eels from suppliers in Holland, where wild caught glass eels, translucent worm-like babies, are reared in aquaculture facilities to a decent size before being killed. Like oysters, eels have gone from being a food of the poor to a dish for the rich. I can vouch for the deliciousness of Japanese unagi.

Eels’ association with London is seemingly acknowledged in the names of local publications like ethical eating mag The Jellied Eel. But whether they are still an ethical eat is debatable. Their populations have crashed by an incredible 99 per cent over recent decades.

The European Eel (Anguilla anguilla) travels on a migration that is “sort of ludicrous,” says John Bryden from charity Thames21.

Born in the middle of the Atlantic, eels waft with ocean currents to the west coast of Britain and over Scotland before hugging the east coast and entering the Thames and its tributaries, where they mature.

After about six years of resting and bulking up they transform themselves into powerful silver eels and swim back to the Sargasso Sea, where it is thought they spawn and die. This is a round trip of some 6,200 miles.

“How that migration ever came about is just beyond me,” says Bryden on a rainy evening at Bow Lock. “There are stories from only 50 or 100 years ago,” he adds, “of people being able to stick a net in a river at the right time and the right tide and pull it out and there would be an elver [a young eel] there, which is just unimaginable now.”

Helped by volunteers, Thames21, the Zoological Society of London (ZSL) and the Canal and River Trust are carrying out scientific surveys aimed at gauging how many eels are now travelling through rivers like the Lea. That there are still any left in the Lea is somewhat incredible given that it is “far from being a normal river,” to quote Bryden. The Lea has been modified to within an inch of its life – changes that might be part of the cause of its eels’ decline.

“A piddly, sperm-like elver…”

At Bow Lock I was shown only my second ever wild eel last month – a piddly, sperm-like elver, but knowing it had travelled such a mammoth distance to be there put my four-mile cycle down a grotty towpath into perspective. It’s not every day you see a critically endangered creature in Bow.

Do eels have any future? Does it matter if they don’t?

“Sad is an enormous understatement,” says Joe Pecorelli, Project Leader for ZSL’s Citizen Science Eel Programme. “It would be a travesty if they disappeared on our watch because they are iconic.

“Culturally they are iconic. They are a species that has been circulating the Atlantic for as long as the Atlantic has existed, so about 80,000 years.

“They are rather robust. They are tolerant of fairly degraded water quality, so it would be an absolute travesty if they were to disappear from our rivers.

“Ecologically they are very significant too – they form part of food webs that our rivers need to sustain a diversity of wildlife.”

The creation of eel passes to allow them to pass through weirs and other barriers that would otherwise be impassable is cause for hope, as are moves to better regulate global fisheries and research eel numbers.

“We have these eel passes and we put little traps in front of them and these stop the eels momentarily,” says Pecorelli. “We check them twice a week and we count the eels coming through, and that gives us an indication of whether the numbers are increasing or decreasing.”

Asked who would volunteer to count eels twice weekly, Pecorelli admits it’s not for everyone and that some people “just think snake.” But he adds: “They don’t appreciate these are absolutely magnificent animals.”