The iconic eels that Eel Pie Island is named after have all but vanished in the River Thames, data has shown.
The prognosis for the European eel is grim, as their population has declined by 98% since 1980.
In 2008 the species were put on the IUCN critically endangered list and signs of recovery are scant.
The project runs an eel trap at Teddington Lock, just downriver from Eel Pie Island, and the most recent data, from 2019, shows that an average of 0.06 eels were caught in the trap per day.
As traps are only manned between the start of April and the start of September, when eels are migrating, this means that over the roughly 150 day period between these months around nine eels were trapped at Teddington.
Although 2019 was a year with a distinctly low catch, across the five years Teddington Lock has been monitored, from 2014 to 2019, the average per day catch of eel was 0.25, or an average of one eel every four days.
There is no disguising the fact that this is not a lot of animals.
Joe Pecorelli, project manager of the Zoological Society of London’s Thames European Eel Project and an “eel obsessive”, described how common eels once were.
He said: “This was once a species so plentiful that it set the margins of rivers black with the wriggling bodies of these young eels coming upstream.
“The data from these traps is not comprehensive. It’s not saying that there’s one eel passing Teddington Lock every four days, it’s not an absolute figure.”
The true number of eels which passed that stretch of water was presumably higher and indeed, other sites in the Thames, like at Moseley record much higher catches than this.
Exactly why European eels face such terminal decline is uncertain, and is probably the result of numerous factors.
Fishing, both legal and illicit, continues to exert pressure on European eels in the UK.
A total of 6,029 kilograms of elvers (young eels) were caught legally in the UK in 2019 according Environment Agency data.
These pressures are heightened by the illegal export market, and the European eel smuggling industry may be worth as much as £2.5 billion.
Pecorelli said: “From ZSL’s perspective eels have innate value, but not everyone sees it that way. There is also commercial value and we have to acknowledge that lots of the conservation work is being done to protect the species because people want to catch them and sell them.”
There is also the problem of industrial pollution, which may lead to eels bio accumulating toxins that interfere with their breeding.
Additionally, ZSL identifies 2,412 potential barriers to eel migration in the Thames river basin district, and sturdy modern constructions are harder for eels to slip through.
A large part of the Thames European Eel Project’s work involves constructing eel passes to help address this.
Their work is administered by a team of citizen scientists, which seeks volunteers from the public.
Pecorelli claimed the dramatic decline of the eel should give us cause to worry.
He said: “If a species that plentiful goes extinct it is sending terrible alarm bells out about what we are doing to the planet, which will eventually affect us all or is affecting us all.”
However, he said there is some cause for optimism as some recent trends in data might just reveal that eels could be making a comeback.
He added: “Whether we will witness the eel fairs of the 1820s again I don’t know. We can dream.”