A Species in Crisis

The European eel was once so abundant that it was considered a staple food source across much of Europe — a common, unremarkable part of river ecosystems. Today, it is classified as Critically Endangered by the IUCN Red List, and recruitment of young eels to European waterways has declined by an estimated 90–95% compared to levels recorded in the 1980s. Understanding why is essential to any hope of recovery.

Major Threats to Eel Populations

1. River Barriers

Weirs, dams, sluices, and other structures fragment river systems and block the natural migration of eels in both directions. Juvenile eels (elvers) attempting to move upstream face physical barriers they cannot pass, cutting off large stretches of historically productive habitat. Adult silver eels migrating downstream toward the sea are killed in turbine blades at hydroelectric power stations — a significant and often overlooked source of mortality.

2. Overfishing & Illegal Trade

Eels have been commercially fished for centuries, but modern fishing pressure — combined with the high value of live glass eels for aquaculture in Asia — has driven intense exploitation. Glass eel trafficking has become a major illegal wildlife trade issue in Europe, with significant quantities smuggled annually to eel farms in East Asia where farming from wild-caught juveniles remains widespread.

3. Habitat Loss

Drainage of wetlands, channelisation of rivers, and loss of riparian vegetation have dramatically reduced the quantity and quality of available eel habitat across Europe and North America. Areas that once supported thriving eel populations have been rendered inhospitable by agricultural and urban development.

4. The Swim Bladder Parasite (Anguillicoloides crassus)

This invasive nematode parasite — accidentally introduced to European waters from East Asia via eel imports — infects the swim bladder of eels, causing significant damage. Heavily infected eels have reduced swimming capacity, which may impair their ability to complete the demanding transatlantic migration to spawn.

5. Climate Change

Changes to ocean currents — particularly the Atlantic Meridional Overturning Circulation (AMOC) — may be altering the trajectory and survival rate of eel larvae drifting from the Sargasso Sea to European coasts. Warmer freshwater temperatures and altered rainfall patterns also affect eel growth rates and behavior.

What's Being Done?

Conservation responses to the eel crisis are underway at multiple levels:

  • EU Eel Regulation: The European Union's Eel Regulation (EC 1100/2007) requires member states to develop Eel Management Plans with the goal of allowing at least 40% of adult silver eels to escape to the sea
  • Eel passes: Fish passes specifically designed for eels — including bypass channels, brush passes, and tile passes — are being installed at thousands of barriers across Europe
  • Restocking programs: Glass eels and elvers are captured in coastal areas and transported upstream of barriers for release, improving freshwater habitat access
  • Seasonal fishing closures: Many countries have implemented closed seasons or complete bans on eel fishing
  • Research tracking: Satellite and acoustic tagging programs are providing new data on silver eel migration routes and survival rates

What You Can Do

Individuals can contribute to eel conservation in meaningful ways: practice catch-and-release when fishing, report eel sightings to national recording schemes, support wetland restoration initiatives, and advocate for river barrier removal in your local community. Every recovered kilometer of accessible river habitat counts.