The lean cod in the Baltic Sea are getting fat on their side fins again.

DTU Aqua has measured more oxygen in the Baltic Sea around Bornholm than expected during its autumn survey.

Section leader Marie Storr-Paulsen from DTU Aqua has found fatter cod than expected in the catch on the first part of the research vessel Dana's autumn survey in the Baltic Sea. Even though the summer has been warm and rich in algae, there is more oxygen than expected. (Photo: © Maria Botansen, DR) 20 minutes ago.

The researchers from DTU Aqua got quite a surprise when they caught the first cod on the autumn survey in the Baltic Sea.

The cod were significantly thicker than expected.

- They weren't really fat, but thicker than we have seen in recent years, where we have only caught very, very thin cod, says Marie Storr-Paulsen, section leader at DTU Aqua.

> I had feared the worst

The marine environment researchers had expected to see oxygen depletion that was just as bad or perhaps even worse than in recent years, because the summer has been warm with very large occurrences of blue-green algae around Bornholm.

- I had feared the worst, so it was a pretty big surprise when we went out and saw that there was oxygen at many of our deep measurement stations, says Marie Storr-Paulsen.

* All cod are checked from top to bottom when Marie Storr-Paulsen needs to see the condition of the stock. And it is good this year. (Photo: © Maria Botansen, DR)

* A lot of cod are being hauled up from the Baltic Sea, so the researchers have something to work with on the research vessel Dana. (Photo: © Maria Botansen, DR)

* A number of fish have to be cut open and examined to see how they are actually doing. (Photo: © Maria Botansen, DR)

* The research vessel Dana has a number of points in the Baltic Sea around Bornholm that are examined on both the spring and autumn surveys, so there is always an updated picture of the sea's condition. (Photo: © Maria Botansen, DR)

1 / 4 All cod are checked from top to bottom when Marie Storr-Paulsen needs to see the condition of the stock. And it is good this year. (Photo: © Maria Botansen, DR) 1 / 4 A lot of cod are being hauled up from the Baltic Sea, so the researchers have something to work with on the research vessel Dana. (Photo: © Maria Botansen, DR) 2 / 4 A number of fish have to be cut open and examined to see how they are actually doing. (Photo: © Maria Botansen, DR) 3 / 4 The research vessel Dana has a number of points in the Baltic Sea around Bornholm that are examined on both the spring and autumn surveys, so there is always an updated picture of the sea's condition. (Photo: © Maria Botansen, DR) 4 / 4

She expects that the Baltic Sea around Bornholm received fresh oxygen from the western part of the Baltic Sea as early as spring. The extra oxygen has allowed bottom-dwelling animals to grow large and ready to eat, so the cod have had something to live on over the summer.

At the same time, some of the bad, oxygen-poor seawater has been pushed away.

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The development can quickly reverse again

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But even though the results are positive, it can quickly reverse again.

- We still have large areas in the eastern part of the Baltic Sea where oxygen depletion occurs very quickly, says Marie Storr-Paulsen.

Read also: Cod in the Baltic Sea are starving: 'Their stomachs are completely empty' ( https://www.dr.dk/nyheder/indland/torsk-i-oestersoeen-sulter-deres-maver-er-helt-tomme )

The research vessel Dana is halfway through the autumn investigations of the Baltic Sea's condition, and now the journey continues from a stop in Rønne Harbor and eastward.

When those results are in, they will be included in an overall overview of the Baltic Sea's condition with measurements from the other Baltic Sea countries.

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