Are grey seals moving into Stockholm's archipelago for food?
Grey seals are turning up farther inside the Stockholm archipelago. Could it be about herring? Scientists are asking, and the key word here is "asking".
Grey seals are appearing farther into the Stockholm archipelago, and scientists are investigating whether changes in Baltic herring could be part of the reason. The cause is not established yet. That is the honest answer for now.
A project led by the Swedish University of Agricultural Sciences is looking at how large-scale herring fishing may affect the coastal ecosystem, including grey seals and cormorants.
Why would a seal change its route?
In the Baltic Sea, herring is a key food for grey seals. The researchers are asking whether fewer large herring could draw seals closer to shore, where other fish are on the menu.
This links one animal's dinner to a whole food web. Imagine seals and cormorants eating more coastal pike and perch. That could ripple down to sticklebacks, then to small grazers, and even to algae.
What are scientists measuring?
The project uses existing environmental monitoring data, plus public sightings of seals and cormorants reported in Sweden's Artportalen. The work began in 2024 and is scheduled to run through December 2026.
The researchers note that fishers and managers have raised concerns about a link between offshore trawling and coastal wildlife. This study brings scientific methods to a question that has been argued about locally for a while.
What can you do as a visitor?
If you spot seals, watch quietly from a respectful distance. Do not approach resting animals, especially pups. Our Sweden ocean guide has more regional context.
You can also read about the grey seal, or why watching is different from interacting.
The seal is what you see at the surface. The real question reaches all the way down, into what is happening in the open Baltic.
Questions people ask
Why are grey seals appearing farther into the Stockholm archipelago?
Scientists are investigating whether changes in Baltic herring could be part of the reason. The cause is not yet established.
Is trawling the proven cause?
No. The researchers describe the links as possibilities the project will test, not conclusions already reached.
What data does the project use?
Existing environmental monitoring data and public sightings of seals and cormorants reported in Sweden's Artportalen. The work began in 2024 and runs through December 2026.
How should I watch seals?
Watch quietly from a respectful distance. Do not approach resting animals, especially pups.
Wildlife encounters are never guaranteed and never forced. Ocean Calling works only with vetted, ethical local operators, and every animal is free to approach, or not, entirely on its own terms.
Sources & further reading
Further reading on Ocean Calling: Sweden in the Ocean Atlas · Grey seal · Atlantic herring · Baltic herring, seals and the coast
Find the retreat that fits you
Small groups of up to six guests, unhurried days and local experts. Tell us how you feel in the water and we will point you to the right trip.