Biodiversity Fact File: The European Eel

Tuesday 1st March 2016

European EelEuropean Eel. Jack Perks

Part of our series of biodiversity fact files looking at species that appear locally and are considered "at risk"

The European Eel (Anguilla anguilla) one of the animals considered to be Critically Endangered on the IUCN Red List of Threatened Species and the OSPAR Convention.

It was listed on Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) in 2007.

Historically, the European Eel was farmed in the UK and other parts of Europe by catching juvenile eels and raising them.

The spread of this trade internationally is believed to have contributed to the decline in wild populations. Since 2009, exports outside of Europe have been banned due to concern over the decline in recruitment and stocks, however, trade continues within the EU and from non-EU countries within its range to other non-EU countries.

Factfile

The European Eel is one of a few species that spend most of their lives living in freshwater, but journey to saltwater in order to breed.

All European eels breed and lay their eggs in the Sargasso Sea, some 3,000 miles away in the western Atlantic.

The larvae from the newly hatched eggs head eastward across the Atlantic, increasing in size as they travel towards the coastal waters of Europe.

By the time they reach the Irish Sea they have transformed into young transparent eels known as glass eels.

When they reach freshwater in the mouth of the Island’s rivers such as the Sulby, the Neb and the Dhoo they then transform again into elvers which are yellowy/brown in colour.

From here they swim upstream into the streams and ditches where it can take between 5 to 20 years for them to mature, becoming darker in colour with white bellies.

These eels are nocturnal, burying themselves in the mud during the day and hunting at dusk.

They have a varied diet: Adults mostly feed on invertebrates, fish and scavenge on decaying fish; juveniles eat insect larvae, molluscs, worms and crustaceans.

They usually grow to about 2ft long, are remarkably agile and strong, and have even been recorded during periods of rain, or even just a heavy dew, ‘swimming’ short distances across land in order to reach ponds and lakes that are not connected to the river courses.

Remarkably as the fully grown eels become sexually mature, they start the 3,000 mile migration back down the river system, out into the Irish sea and all the way back to the Sargasso Sea in order to breed, and as a result are one of the longest distance migrants that regularly visit our island.

This long distance migration however makes them extremely vulnerable to predation, pollution, and fishing impacts.

At the same time, many of the freshwater habitats where they naturally live and grow to adults are fragile – being affected by drainage, pollution or put out of reach by river engineering structures such as weirs and sluices.

More information

Read about European Eels on the IUCN Red List website

Find out more about our island's biodiversity

Read about the Isle of Man government's biodiversity strategy

Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES)

OSPAR Convention

Photos: top: Jack Perks; middle & bottom: DEFA

Tagged with: Biodiversity, European eels, Freshwater, Marine