Aarhus University Seal / Aarhus Universitets segl

Satellitetagging

of harbour seals and grey seals

Seals are shy animals that spend most of their time submerged in water. The best way to study their behavior is by tagging them with a satellite tag. The tag gives away their GPS position and scientists can follow their movement online. The transmitter must be above the water to be able to transmit, and it is therefore most effective to place the transmitter on the head of the seal because seals often stick their head above the water to breathe. The transmitter can stay on the seal until May/June, when the seals molt their fur.

Telemetry by satellite is the most common way to track and monitor seal species. This tagging method helps us to better understand where seals forage, how long they stay on land during the different seasons of the year and how they react to areas with heavy noise and reconstruction. Monitoring seals by using satellite transmitters has already shown us that movement patterns vary between different species and ages. For scientist to get the best representative data, it is essential to track a larger number of individuals with different ages during multiple years. In our section, we take part in a couple of ongoing projects with both grey seals and harbour seals. Together, this information will provide a clear picture of patterns and connections between behavior, movement and the spread of different diseases. 

More knowledge about seal foraging patterns close to conventional fisheries, the spread of diseases and general behavior gives us a better opportunity to construct efficient conservation-strategies and initiatives in the future.

Seals in Streams - Limfjorden

Background

Investigations of harbour seal in Limfjorden and Karup Å, and their impact on the Karup Å trout stock    

The harbour seal is most often found in Danish marine waters, but is also frequently observed in rivers and streams across the northern hemisphere. Harbour seals naturally swim up freshwater streams in search of food. This has particularly caused conflicts with anglers, who experience a decreasing catch rate when seals are present. The purpose of these studies is to investigate the harbour seals’ impact on the trout stock in Karup Å through diet analysis from seals and mapping of seal occurrence and movement in the areas close to the stream. Two non-lethal mitigation methods, seal scarers and electrical fields, are investigated and evaluated for potential implementation: Seals in streams.

The scientific purpose

To investigate:

  • Seasonal variation in behavior
  • Movementpatterns
  • Fouraging areas
  • Resting areas and time spent on land
  • Effects from noise and environmental changes

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A harbour seal tagged on Anholt
Tagging a harbour seal at Anholt, Photo by AU
Tagged harbour seal
The tagged harbour seal is released photo by AU