Forgotten fish: Saving the Legendary European Eel

The European eel

Elusive, mysterious, and beautiful in its own way. Highly prized for its delicious flavour. Not so long ago, rivers teemed with these magnificent snake-like fish. Entire communities depended on them for sustenance. They are deeply embedded into human culture. For centuries, people have celebrated this remarkable animal.

Today, the eel’s story is less often heard. Facing devastating population collapses, the eel has started to vanish not only from our waters, but also from the public consciousness. Lurking in the depths of riverbeds, perhaps they are easily forgotten without a steady supply of them on our dinner plates.

What’s special about eels?

Many people have never seen a live eel before. Those who have seen one most likely found it at the bottom of a muddy river, covered in slime. In this context, eels do not seem very special, nor elegant. But they possess many surprising abilities, and their biology continues to mystify scientists.

For centuries, their remarkable life cycle was unknown to humanity. As recently as 1862, engineer and naturalist David Cairncross of Dundee published a book in which he claimed that eels spend the first part of their life cycle as a beetle, before developing into their eel form. An old English myth tells that eels grew from the hair of horses’ tails that fell into the water.

We are now fortunate enough to have figured out how eels live, at least in part.

Eel life cycles

All eels begin their lives in the Sargasso sea, a region of the Atlantic Ocean encapsulated on all sides by a powerful ocean gyre. Here, the young eel larvae are hatched. Ocean currents carry their tiny fragile bodies, no larger than a 5p coin, to Europe or North America. They drift for thousands of miles, their journey lasting up to two years.

By the time they reach the continent, the eels have grown into their post-larval form. They are called glass eels now. Their magnetic compass helps them orient themselves against the tidal forces, as they battle their way upstream in estuaries.

In the brackish water of estuaries, they metamorphosise into juvenile elvers. Once their pigment develops, the young elvers migrate into freshwater rivers, where they will remain for the next decade.

Eels sometimes wander onto land, and can survive for many hours out of water

Eels remain quite sedentary once established in a river. During the day, eels hunt for all kinds of prey – shrimp, snails, mussels, caddis flies and midge larvae – to name a few. Adult eels have even been found with mice and birds in their stomachs. It seems the only thing limiting their diet is the size of their heads. If their meal is too large to swallow whole, they will hold the prey in their jaws and spin rapidly to tear off flesh. They prefer their food alive or recently dead - but will not eat anything rotten. By night, or when the water temperature drops below 14C, eels become inactive.

One day, up to fifteen years after they entered the river, something drives the eels to up and leave. The adults navigate back to their birthplace in the Sargasso Sea, guided by their remarkably refined sense of direction. Here they will breed and die, to continue the cycle once more.

Why do eels migrate so far?

We are not entirely sure what drives them to travel thousands of miles, simply to rest beneath a chosen rock in a particular river on the other side of the world. Not just once, but twice in their lives this journey is made. It is long way for a small fish to travel, given the number of predators that would gladly eat it.

A grey heron swallowing a European eel at Leighton Moss RSPB, August 2019

It is thought that continental drift over millions of years, leading to the separation of Europe and North America, has resulted in the formation of two distinct species of eel. The American eel and the European eel both hatch in the same region of the Sargasso and make their separate ways to their respective continents. Aside from the number of vertebrae, these two species appear identical. It could be that eels used to have a much shorter journey to the continent but have slowly adapted to continental drift. Perhaps they are just very fond of their traditions?

How do the eels know where to go?

We are not entirely sure how eels navigate. But what we do know, is that eels have one of the sharpest senses of smell in the animal kingdom. Their ability to sense the Earth’s magnetic field may also help to guide them. This is one of the many unanswered questions about the eel.

People and eels – cultural significance

“Human appreciation of eels has never depended on our understanding the how, where or why of eel biology, but rather on their full rich flavour and easy availability.”

Richard Schweid in his book, Eel. (Link)

There is much archaeological evidence which demonstrates that people’s love for eels goes way back. They are frequently alluded to in Greek poetry. In Ancient Egyptian society, eels were sacred to the god Aton, and mummified eels have been found, complete with their own luxurious “eel coffins”. Eel bones have been found in palaeolithic caves in France, and carved stone decorations and wall art featuring eels has been found at these sites too. In 1951, a harpoon for catching eels was found in Northern Ireland and dated to 5725 BC.

Woodcut of the European eel from 1555

All of this shows that people have eaten eels for a long, long time. Due to their unusually high fat content, they are reportedly very delicious. They spend around a decade building this fat reserve to prepare for their journey back to the Sargasso sea. And they were once a very numerous and readily available source of human nutrition. Eels were copiously eaten on the streets of England and France in the 1300s, in the form of eel pasties, eel pies and eel kebabs – think Greggs, but with more eels. The upper classes and nobility were not immune to the temptation of eels either, and would eat them fried with garlic, saffron and parsley topped with a fine wine puree. Eels were so common that people would complain about having to eat them too often.

What went wrong? What happened to all the eels?

We now know that just because a species is common, does not protect it from the threat of extinction. Today, European eels are classed as critically endangered, and the closely related American eel faces similar threats. This decline is a result of many factors, including overfishing, parasites, the damming of rivers, pollution, and changes in ocean currents. The number of glass eels arriving to Europe has declined by 95% in just forty years. This is an alarming wake-up call, especially considering that the eel once constituted 50% of all freshwater fish biomass in Europe.

Can’t eels be farmed like salmon?

There are great incentives to develop aquaculture techniques for eels. The eel industry is worth billions in countries where eel is still widely eaten, such as Japan. Despite all the effort and money put into breeding eels in captivity, attempts at eel aquaculture have not been successful yet. While it is possible to capture class eels and raise them to table size, it seems that eels will not reproduce in captivity. Eggs fertilized in vitro have yielded larvae, but these larvae do not survive longer than a few days.

What can we do to help eels?

The battle to save the eel is not over – it has only just begun. People from all walks of life are coming together to celebrate the eel and fight for its conservation. This story is one that remains unwritten – it is up to all of us to determine how it will end. Below are some of the fantastic organisations and projects which have inspired and helped eel conservation. If you care about eels, why not get involved?

A Suitcase Full of Eels is a creative collaborative project in which artists and academics have come together to engage with the European Eel in a playful way. The project features artwork, poetry, stories and more - all available to explore freely on their website. Their work helps spark discussion and raise awareness of eels, which is a crucial step towards informing policymakers and environmental managers.

The Sustainable Eel Group is a “Europe wide science led organisation” which works exclusively towards eel recovery and conservation. They run a number of educational events and conferences to bring academics, industry and policymakers together. They work closely with governments and other NGOs, and have achieved significant media publicity for their work.

The Eel Stewardship Fund exists to help pay for activities that directly help eel populations. This money is used help towards move glass eels from polluted rivers to healthy waterbodies where they have a greater chance of survival. It also pays for migrating silver eels to be trapped and transported unharmed to the ocean, to help them along their journey back to the Sargasso. The fund may also pay for eel tunnels to help eels cross weirs and dams. Licensed eel products bearing the Eel Stewardship Fund logo donate a portion of their profits into the fund.

Example of an eel pass

The Wildfowl and Wetlands Trust is a UK based charity aiming to conserve and restore wetlands. Several of their reserves are home to eels and they carry out habitat management to improve the conditions for the eels. Their work also includes helping glass eels to migrate all the way to the reserve using “eel pass” tunnels. They are also microchipping eels to contribute to the understanding of their migration. If you spot an eel in the wild, this can be reported to the WWT to help them with understand and improve their reserves.

A conservationist holding a glass eel

And finally...

If you are interested in outdoor conservation work and live near Edinburgh, the Forth Rivers Trust are looking for volunteers to help with tasks including river monitoring, practical conservation days and invasive species control. The Water of Leith Conservation Trust is another excellent charity you could get involved with locally. You could help to clear up the river, run their volunteer centre, or carry out river patrolling to help inform the conservation work (check their websites for updated information on this).

Written by Erika Hodgson

All images licenced under Creative Commons (CC BY 4.0).