Födosöksaktivitet hos juvenil europeisk ål (Anguilla anguilla) i olika bottensubstrat

Sammanfattning: The European eel is critically endangered (IUCN 2021), only 1% of the population remains and the recruitment has been estimated to be 5-10% of their historical values. The eel is in dire need of remedial efforts and many studies suggest that these efforts are best applied to elvers when these have ended their migration. To satisfy the need for suitable habitats of elvers, we need to understand which habitat is best suited to increase survival and growth. This study focuses on how habitat use of elvers, specifically use of gravel and sand bottom substrates, influences behaviour and activity. In a laboratory experiment, eels in aquaria with gravel substrate were 33 % less visible and had 50 % lower levels of observed activity than eels in aquaria with sand substrate. This difference in visibility and activity has implications for survival by affecting the ability to avoiding visual predators. If we can increase the chances of survival of elvers by strategical placement of gravel substrate as a remedial measure, we could be adding to the recovery of the population.