Reproductive biology of the European eel

The European eel is a fish species with a remarkable life cycle. However, for many years now, its stock situation is a reason for major concerns. Until today, it is not finally clarified why the recruitment of young eels, so called glass eels, was strongly declining over the last 30 years and which measurement are feasible to ensure the future sustainable use of this species that is important for both, inland and coastal fisheries.

The biggest knowledge gaps are found within the field of reproductive biology and during the oceanic life phases. In order to find answers to the open questions we regularly study the larval distribution in the Sargasso Sea, the spawning area of the European eel, thousands of kilometres away in the Western Atlantic. We investigate how oceanic factors influence larval abundance and distribution, try to get insight into larval feeding ecology and study the behaviour of eels during the marine phase of the spawning migration.

In future, these field studies will be increasingly accompanied by laboratory experiments, like e.g. the use of pressurized swim tunnels to test the effects of external factors (e.g. pressure, pollutants, parasites) on energy consumption and gonadal development of silver eels. In another perennial experimental study at the Thünen Institute of Fisheries Ecology we aim at maturing eels in captivity and producing first feeding larvae. In cooperation with different institutes we are developing potential feeding items for the larvae during this project and investigate the maternal transfer of contaminants into eggs and embryos.

The acquired knowledge should help to better explain fluctuations in glass eel abundance and promote the artificial reproduction of eels.