First mature European eels recorded in Cyprus rivers

Researchers have recorded mature European eels in Cyprus’ inland waters for the first time, marking what they describe as a significant moment for conservation efforts in the eastern Mediterranean.

The study, led by Bournemouth University in collaboration with the University of the Highlands and Islands, the Cyprus University of Technology (Tepak) and the Environment Agency, identified European eels (Anguilla anguilla) at the silvering stage of their life cycle in rivers on the island.

Silver eels – the mature phase in which the species migrates back to the ocean to spawn – have previously been recorded across parts of Europe and as far east as regions of Turkey, but never before in Cyprus.

Lead researcher Sotiris Meletiou said the discovery confirmed that the species has not only survived in Cypriot rivers but has grown to maturity there.

“After spawning in the Sargasso Sea in the Atlantic, European eels arrive in continental waters as tiny glass eels. They spend many years developing in freshwater habitats before transforming into the silver eel stage, which migrates back to the ocean to reproduce,” he said.

“Because little information exists on silver eels in the eastern Mediterranean, our surveys in Cyprus specifically targeted habitats and periods where silvering and migration were most likely to occur. We confirmed that mature silver eels are present and migrating at the easternmost edge of the species’ range.”

The European eel has suffered a dramatic population decline over the past century due to pollution, habitat loss, extreme weather events, parasites and overexploitation.

Numbers of the species, classified as “critically endangered” on the International Union for Conservation of Nature Red List since 2008, are estimated to have fallen to around 10 per cent of historic levels.

One of the sites where mature eels were found was the Polis river in the northwestern Paphos district. Researchers captured eels at several points along the river, demonstrating that juveniles are successfully travelling upstream to develop.

However, the team observed that fragmentation of the river – including stretches that had dried up – was hindering upstream movement and delaying downstream migration for some individuals.

Dr Demetra Andrea, an environmental science academic involved in analysing the survey data, said the findings highlight the impact of river fragmentation and local environmental conditions on eel populations.

“In the river we can see that this is preventing effective escapement of silver eels and directly reducing their contribution to spawning populations in the Sargasso Sea,” she said.

Under European Union legislation, member states are required to develop eel management plans to support the recovery of the species.

Cyprus is currently exempt from this obligation.

Dr Malen I. Vasquez of Tepak said the presence of all eel life stages in what appears to be an unexploited population offers an important opportunity.

“The discovery provides Cyprus with the chance to contribute to the recovery of eel populations in the region,” she said, adding that the development and implementation of a national management plan is urgently needed.

Ros Wright of the Environment Agency’s national fisheries services team said the survival of eels to the silvering stage in areas affected by habitat loss, limited connectivity and extreme drought conditions sheds light on the species’ resilience in the face of climate pressures.

The study also makes recommendations for improvements to barriers and structures in rivers and lakes to facilitate safer upstream and downstream migration, in a bid to strengthen the long-term survival of the species in Cyprus.