Media: Norway’s fish farms pollute fjords with sewage-level waste

Norwegian salmon farming is releasing nutrient pollution into coastal waters at levels comparable to the untreated sewage of tens of millions of people annually, according to a new report that has raised concerns over environmental damage in the country’s fjord systems.

Norway, the world’s largest producer of farmed salmon, discharged an estimated 75,000 tonnes of nitrogen, 13,000 tonnes of phosphorus and 360,000 tonnes of organic carbon into coastal waters in 2025, the Sunstone Institute found, The Guardian reports.

The nutrients originate largely from uneaten feed and fish waste in open-net pens.

The report said the combined impact of these emissions is equivalent to the untreated sewage of 17.2 million people for nitrogen, 20 million for phosphorus, and 30 million for organic carbon.

“Norway is a small country of just 5.5 million people, and the output of aquaculture pollution in terms of these three nutrients is three to five times larger than the population,” said Alexandra Pires Duro, a data scientist at Sunstone and author of the report.

“The faeces, the uneaten feed, the urine – everything goes into the water.”

The analysis was based on data from national fisheries and veterinary authorities and examined nutrient inputs from fish feed used in open-net salmon farming. Researchers said feed consumption rose by 14.6% over six years, tracking industry growth and increasing nutrient discharge into surrounding waters.

The report warned that seasonal peaks in summer intensify the environmental pressure, when ecosystems are less able to absorb excess nutrients. This can contribute to eutrophication and harmful algal blooms that deplete oxygen in the water.

Fish sludge and nutrient runoff can stimulate phytoplankton growth, which later decomposes and consumes oxygen as it sinks, worsening conditions in enclosed fjord environments.

In Sognefjord, Norway’s longest fjord, nutrient inflows – alongside rising sea temperatures – were linked to about two-thirds of observed oxygen depletion in a study last year. The remaining decline was attributed to warming waters driven by climate change.

Oxygen levels have also fallen in the Hardangerfjord, the country’s second-longest fjord, according to regional authorities in Vestland.

Environmental concerns have already influenced policy decisions. In March, regulators rejected nine fish farm applications in one fjord region due to expected emissions.

“The major concern we experienced in the last few years is that all these algae and plankton and whatever die and they sink down to the bottom of the floor and they decompose – and that process uses oxygen,” said Tom Pedersen, an environmental adviser who reviewed the Sunstone report. “The end result is that the oxygen level in the fjord is going down, and has gone down.”

The Norwegian fisheries ministry declined to comment, referring inquiries to the national fisheries directorate.

The Norwegian Seafood Federation defended the industry, arguing that production supports national food security and is managed within environmental limits.

Krister Hoaas, head of public affairs at the organisation, said: “It is important to distinguish between current operations and questions about future growth.”

“The Institute of Marine Research is clear that a significant increase in production in certain fjord systems could increase the risk of eutrophication locally, but that current production is well within nature’s carrying capacity. This provides a basis for strict, site-specific management, but does not document that current operations are destroying the fjords.”