Emigration of European silver eel (Anguilla anguilla L.) from a polder system into the Schelde estuary

Connectivity between freshwater habitats and marine areas is heavily obstructed by migration barriers, leading to a high pressure on diadromous eel populations. Migration barriers attribute to the 98% decline of the European eel (Anguilla anguilla L.) population. A better understanding of eel behaviour regarding these barriers is needed for water managers to take proper mitigation actions. We tracked 50 eels by means of acoustic telemetry between July 2012 and January 2015 and analysed their migration behaviour in a Belgian polder area. On their way to the Schelde Estuary, eels face several migration barriers such as a pumping station, a weir and tidal barriers. The telemetry study did reveal significant delays and searching behaviour near those barriers. Depending on nothing but their accumulated fat, delays can have a serious impact on the fitness of the eel by wasting precious energy resources needed for a successful trans-Atlantic migration. In addition, delays and searching behaviour can also increase predation risk. The obtained knowledge can contribute to efficient management such as improved fish passage and guidance solutions.Connectivity between freshwater habitats and marine areas is heavily obstructed by migration barriers, leading to a high pressure on diadromous eel populations. Migration barriers attribute to the 98% decline of the European eel (Anguilla anguilla L.) population. A better understanding of eel behaviour regarding these barriers is needed for water managers to take proper mitigation actions. We tracked 50 eels by means of acoustic telemetry between July 2012 and January 2015 and analysed their migration behaviour in a Belgian polder area. On their way to the Schelde Estuary, eels face several migration barriers such as a pumping station, a weir and tidal barriers. The telemetry study did reveal significant delays and searching behaviour near those barriers. Depending on nothing but their accumulated fat, delays can have a serious impact on the fitness of the eel by wasting precious energy resources needed for a successful trans-Atlantic migration. In addition, delays and searching behaviour can also increase predation risk. The obtained knowledge can contribute to efficient management such as improved fish passage and guidance solutions.C