EELIAD: European eels in the Atlantic: Assessment of their decline
Funded by the Framework 7 Research Programme (European Union) The Eeliad project, is an EU-funded project investigating the marine migrations of European eels and assessment of the most important factors that influence silver eel production and migration success. Scientists from six European countries are collaborating on the project investigating the decline of European eels. The European eel (Anguilla anguilla) is a species very much under threat, with numbers in catastrophic decline. This is seen in the fisheries for yellow and silver eels, as well as in surveys of the number of glass eels that are returning to Europe. The decline can be tracked back to the early 1980s and considerable effort is now needed to reverse the situation. In consequence, the EU established the Eel Stock Recovery Plan in 2007 in an effort to reverse the decline, with Member States required to implement national management plans that will safeguard eel populations and their habitats. Commercial fishing for eels has been suspended, and anglers cannot retain eels anymore. Reasons for the decline are unknown, but man-made impacts like habitat destruction, fishing, pollution and climate change are thought to be having an effect. Improving our understanding of some of the critical aspects of eel biology and ecology, and how they relate to both natural and man-made impacts, is the focus of the eeliad project. Scientists have also speculated that a new parasite which infects the swim bladder of eels may be affecting their migration at sea, where the swim bladder is important for depth regulation. To prove this theory, it is necessary to follow the eels on this journey to see how they are behaving and whether they survive to reach the spawning grounds. The Eeliad programme focuses on improving our knowledge of some aspects of the life history of the European eel (Anguilla anguilla). This knowledge is of direct use in policies aimed at conservation of the eel stocks because it will help to assess some of the potential reasons for the recruitment failure, e.g. poor quality and migration success of silver eels, and to identify the characteristics of those areas which produce silver eels of sufficient quality to achieve successful migration to the spawning grounds. To date scientists have never proven where eels actually go to spawn at sea. For many years, it has been assumed to be in the Sargasso Sea, as larval eels have been found here in greater numbers than anywhere else. But adult eels have never been observed here. The Sargasso Sea is over 5,000km from Ireland, a truly epic journey for an animal between 40-100cm long, swimming against prevailing ocean currents. So, aside from the benefits to eel management, following adult eels all the way to the Sargasso would be a huge achievement for science, and finally prove the Sargasso theory. Under this European programme a number of migrating silver eels have been tagged in Ireland with Pop up Satellite Archival Tag (PSATs) for the last three years and scientists have followed the path of the eels for 2,200km as far south as the Azores. The tags are programmed to detach after a certain time, and transmit the data recorded to a satellite. Data recorded includes information on temperature and the depth the eels swim at, and has shown the eels can dive to 1000 meters below the surface during the day, coming closer to the surface at night time, probably to avoid predators and regulate their body temperature. Large silver eels are selected from different catchments taking into account the known presence or absence of the swim bladder parasite Anguillicoloides crassus. Eel tagging takes place at the Galway eel fishery. Biological data is also been collected from eels and ongoing work includes the analyses of contaminants, parasites, viruses, hormone levels, diet and eel aging using otoliths. This research programme will provide important scientific information on the decline of eel stocks across Europe, and will help fishery managers decide on strategies to maximise eel survival to their ocean migration stage. Further InformationDr. Patrick Gargan (Senior Research Officer) / Dr. Gustavo Becerra-Jurado (Research Officer) Project publicationsAarestrup, K., Okland, F., Hansen, M. M., Righton, D., Gargan, P., Castonguay, M., Bernatchez, L., Howey, P., Sparholt, H., Pedersen, M. I. & McKinley, R. S. (2009). Oceanic Spawning Migration of the European Eel (Anguilla anguilla). Science 325, 1660. |
