May 6, 2026, 3:21 p.mMay 6, 2026, 3:47 p.m
Norway is the world’s largest producer of farmed salmon. The country produces over 1.2 million tons annually. In addition to oil and natural gas, fish farming (aquaculture) is the country’s most important economic sector.
The aquacultures are located in open net cages in the sea, allowing nutrients to flow directly into the sensitive fjord systems.Image: Shutterstock
But the economic success has an ecological downside: Norwegian salmon farms heavily pollute the country’s fjords and coastal waters with nutrients from fish feces, leftover feed and urine. Analyzes revealedthat Norwegian aquaculture released 75,000 tons of nitrogen, 13,000 tons of phosphorus and 360,000 tons of organic carbon last year.
To illustrate: Norway dumps so many nutrients into the sea that it can be compared to the raw sewage of the whole of Australia. Australia has more than 21 million more inhabitants than the Scandinavian peninsula.
The waste ends up directly in the sea because the fish are kept in open net cages. At first glance, nutrients seem harmless or even positive, but in large quantities they can have a significant impact on the environment.
Changing entire ecosystems
Nitrogen and phosphorus act like fertilizer. If too large quantities get into the water, algae grow heavily and so-called algae blooms occur. The water can turn green, brown or red and the ecosystem becomes unbalanced.
It becomes particularly critical when the algae die off again, because then they are decomposed by bacteria. Oxygen is consumed in the process. This can lead to a lack of oxygen, especially in the fjords, as the semi-enclosed waters have only narrow connections to the open sea. This means that only a small amount of fresh, oxygen-rich water is supplied. Fish and other creatures can suffocate or migrate. Global warming makes the problem even worse: warmer water can absorb less oxygen, so oxygen deficiency occurs even more quickly.