By Sarah Mukherjee
Environment correspondent, BBC News
The number of young eels in the Severn has fallen by 70% in recent years
The Severn is a wide expanse at this point on the river.
Silvery grey in the morning mist, the surrounding hills are tinted lavender by the morning sun.
There is a crowd here, waiting for the Severn Bore, a tidal wave that comes up the river and is at its strongest at this time of year.
Surfers are polishing their boards and canoeists launching themselves in to the middle of the water.
But it is not the wave we are here to talk about, but a curious creature that spends much of its life in these slow-moving waters.
I am standing on the banks of the river at Epney with Andrew Kerr, the chairman and prime force behind the Sustainable Eel Group.
Very little is known about the eel, and, as Andrew says: "The more we find out, the less we know."
The Severn Bore is one of the best examples of its kind in the world
It has never been seen breeding, although it is believed it mates in the Sargasso Sea, just north of Bermuda. No adult eel, however, has ever been found in the area.
This sea supports both the European and American eel - but nobody knows how each species ends up making its respective long journey across the oceans, drifting on the fast-moving currents.
For the European eel to get here takes about two years, and until recently, baby, or glass eels, would teem up the rivers of the UK.
"The scale of their abundance was overwhelming," says Mr Kerr.
"Entire communities would live on them; indeed at this point on the Severn they were even used to fertilise the fields."
But, just as the life of the eel is as opaque as the depths of the oceans in which they make their mammoth journeys, so is the rapid decline in numbers that fishermen and conservationists have reported on rivers and waterways and lakes across Europe.
"We're talking about relative decline here," says Mr Kerr.
"This is not a tiger, with only a thousand left. There will still be millions of glass eels in the Severn this year.
"But there is no doubt that the scale of decline has been dramatic - a 70% reduction overall."
A European recovery plan was put in place in 2009 by the European Commission.
It required all countries to create "eel plans" for their river basin districts which would allow recovery and its sustainable use for food, and ensure that enough adult eels would make the journey back to their spawning grounds.
It also was supposed to ensure that all EU countries reserved a certain number of eels for conservation and restocking work across the 27-nation bloc.
But it appears that some countries are taking this more seriously than others. The French, for example, have a quota of 15 tonnes of glass eels, about 50 million of them, that they can sell to the lucrative trade in China, where they are eaten.
But they were also supposed to reserve, in the course of the season, about 12 tonnes for restocking European rivers. This has not happened.
"This means that the restocking requirements from the northern and eastern European countries will not be met because the season is drawing to a close.
"It means that many countries' EU plans, which were dependent on restocking, cannot be achieved."
A spokesman for the Department for Environment, Food and Rural Affairs (Defra) says the government agrees with conservation groups that there should be an export ban to countries outside the EU for whatever purpose.
But a spokesman said that the UK would not have to rely on French eels for restocking.
Andrew Kerr disagrees: "Two million eels have already been sent to Loch Neagh in Northern Ireland from France, purchased before the price rocketed as a result of the Chinese exports.
"For the first time ever, the Severn is unlikely to be able to meet the restocking requirements of the Loch Neagh fishing co-operative."
The surfers are waiting for the Bore, looking for all the world like basking seals in the middle of the river.
A sign close to us on the bank says this stretch is reserved for private elvering - or eel catching.
This river was once literally alive in springtime with eels; conservationists worry that this natural phenomenon may soon be a thing of the past.