Polder areas are lowland systems below sea level that are drained for agricultural and urbanization purposes. Hence, they are characterised by water regulating structures such as dykes, water pumping stations and weirs. They are characterised by a network of canals, connected ponds and ditches, resulting in a high habitat diversity and thus many potential growth areas. When the water level rises beyond a certain threshold during precipitation events, water is pumped from the polder area into the sea to maintain a specific water level. Not only does this result in irregular water flows, water pumping stations have already shown to negatively affect fish passing through them by various injuries and mortalities. In this tracking study, we investigated the movement and ranging behaviour of resident, yellow eels to understand their spatio-temporal habitat use in the polder. Second, we analysed what routes migrating silver eels take, what environmental factors influence this migration and to what extent they are delayed by the migration barriers.

This dataset was collected using infrastructure provided by VLIZ and INBO funded by the Research Foundation - Flanders (FWO) as part of the Belgian contribution to LifeWatch. The study was commissioned by the Agency of Nature and Forest (ANB). Data were exported from the European Tracking Network data portal (http://www.lifewatch.be/etn) developed by VLIZ using the ETN R package (https://inbo.github.io/etn/) developed by INBO. Field definitions can be found at https://inbo.github.io/etn/articles/etn_fields.html.