Aarhus University Seal / Aarhus Universitets segl

No. 192: Mapping of seals in the Limfjord and adjacent streams

Stepien, E.N., Teilmann, J. & Galatius, A. 2021. Kortlægning af sæler i Limfjorden og tilstødende vandløb. Aarhus Universitet, DCE – Nationalt Center for Miljø og Energi, 20 s. - Teknisk rapport nr. 192. http://dce2.au.dk/pub/TR192.pdf

Summary

The harbour seal (Phoca vitulina) is a marine mammal found in Northern Europe and most Danish waters, except the Baltic Sea around Bornholm. It is frequently observed in rivers and streams throughout its range. Harbour seals naturally swim up larger streams in search for food. This has caused conflicts with anglers in particular, who report a decrease in catch rate when there are seals in the streams, as well as it raises concerns about the effects on the trout and salmon stock. This report investigates the occurrence of harbour seals in the freshwater contributories of the Limfjord from 2008-2020, with a focus on Karup Å. Based on reported observations, interviews, GPS-tracked seals and surveillance of Karup Å, this report shows that the harbour seals do occasionally enter the streams, but that it is most likely a limited number of individuals with little effect on the streams’ stock of trout. Generally, it appears that the occurrence of seals in the streams is higher during years where there is a low number of counted seals at the haul-out sites in the central part of the Limfjord. This may be caused by a low food availability at the central banks, wherefore the seals seek out the rivers to a greater extent.