As part of a new study researchers from Bournemouth University (BU) have discovered European eels, Anguilla anguilla, at the stage of silvering living in the inland waters of Cyprus for the first time.
Silvering European eels have been recorded across parts of Europe as far as some regions of Turkey, but never as far east as Cyprus. The discovery of the eel in its silver life stage in rivers in Cyprus was a key moment for the researchers who realised that the species had survived in this habitat and grown to maturity.
The study was conducted by Bournemouth University, and involved a collaboration between the University of Inverness, Cyprus University of Technology and the Environment Agency.
BU Researcher, Sotiris Meletiou, who led the survey of the eels in Cyprus said: “We know that 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 undergoing a transformation into the silver eel stage, which migrates back to the ocean to reproduce. 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, and confirmed that mature silver eels are present and migrating at the easternmost edge of the species’ range”
The European eel populations have dramatically declined over the past century due to pollution, habitat loss, extreme weather conditions, parasite infections and exploitation. Recorded numbers of this “Critically Endangered” species is estimated to be down to 10 percent since populations were first monitored, putting the species on the IUCN Red List since 2008.
One of the sites where the team discovered mature eels was the Polis River, in the northwestern region of Paphos. Sotiris said: “We were able to capture eels across several sites along this river. This demonstrates that some juveniles are making it upstream to develop. However, we noticed that the fragmentation of the river, where the water had dried up was preventing good numbers of eels moving upstream. This was also delaying downstream migration for some individuals.”
Dr Demetra Andreou, Principal Academic in Environmental Science, part of the UK team analysing the survey data said: “These findings highlight the importance of river fragmentation and local environmental conditions on the populations of the eels. In the River Polis we can see that this is preventing effective escapement of silver eels and is directly reducing the contribution to the eel spawning populations in the Sargasso Sea.”
European Union legislation has mandated the development of Eel Management Plans (EMP) to help conserve their remaining populations. However, currently Cyprus is exempt from an EMP. Dr Malen I Vasquez from Cyprus University of Technology who helped analyse the data from the survey said: “The discovery of all eel life stages of an unexploited eel population in Cyprus provides an opportunity for this island to contribute to the recovery of eel populations in the region. This is the first step in the development and implementation of the EMP, which we suggest is required urgently.”
Dr Ros Wright from the Environment Agency’s National Fisheries Services team said: “The survival of eels to the silvering stage in locations where habitat loss, lack of connectivity and extreme drought conditions prevail are furthering our understanding of the life history and resilience of this critically endangered species in changing and extreme climatic conditions.”
The survey makes several recommendations to freshwater sites where improvements can be made to the barriers and structures of lakes and rivers to help with the successful migration of eels up and downstream.
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