THIS CONTENT IS BROUGHT TO YOU BY NTNU Norwegian University of Science and Technology - read more

Fish farming is least harmful to the seabed in the north

Environmental conditions on the seabed around fish farms generally improve the farther north you go.

Aerial photo of six circular fish farm cages and a workboat on deep blue water.
Researcher Chun-Deng Wang used official Norwegian monitoring data to compare conditions around aquaculture facilities in different parts of the country.
Steinar Brandslet journalist at Norwegian SciTech News
Presented by: Presented by: Presented by: NTNU - Norwegian University of Science and Technology
Published

A study of the environmental conditions around fish farms reveals a surprising trend.

The researchers have focused on how efficiently the feed is used, how much nutrient waste the farms release, and how life on the seabed changes.

“Our results show a significant geographical variation in both feed utilisation and nutrient emissions. Efficiency increases steadily from south to north in Norway,” says Chun-Deng Wang.

He is a researcher at NTNU’s Department of Biology, and this study is part of his doctoral work.

“These differences in efficiency and environmental costs may lead to a gradual shift of aquaculture operations toward the north,” he says.

Line chart showing results
Annual production of Norwegian salmon farming in pens in the southern, central, and northern regions from 2005 to 2022. The regions are defined as follows: the northern region includes Troms, Finnmark, and Nordland. The central region includes Trøndelag and Møre og Romsdal. The southern region includes Vestland, Rogaland, and Agder. Data from the Norwegian Directorate of Fisheries.

Two types of seabed assessments

Norway has introduced regulations for environmental monitoring of how the seabed is affected by aquaculture. These are known as B and C assessments.

  • The B assessment uses simple biological and chemical variables. Samples are taken frequently, within 30 metres of the salmon pens.
  • The C assessment is a more comprehensive examination conducted from 30 to 500 metres away from the pens.

Chun-Deng Wang used official Norwegian monitoring data to compare the conditions in different parts of the country.

Map of Norway with coastal assessment points and pie charts showing regional status ratings.
The orange dots show the locations of salmon farming facilities. The pie charts indicate the environmental status at the county level, based on the B assessment from 2020.

Why does the seabed in the north fare better?

The northern part of the country fares best in this study. This is likely due to water temperature and other physical environmental factors.

“Seabed conditions are strongly influenced by feed utilisation, water depth, biomass density, and the length of the production cycle,” Wang says.

Seasonal variations also play a role.

“Higher feed intake during the summer and autumn appears to have a more pronounced impact on the environment,” he says.

Good news for more environmentally friendly aquaculture

The aquaculture industry has grown rapidly in recent decades, and its environmental impact is a topic of discussion. 

On the one hand, fish farming can reduce pressure on wild fish stocks. On the other hand, it poses a number of problems such as escaped fish, pollution, and unsustainable feed sourcing.

This study brings good news. The findings show that seabed ecosystems can recover quickly, especially when damage is detected early.

It's also clear that the C assessment, which is more comprehensive, is effective at detecting even small differences in how aquaculture impacts the seabed.

“Overall, the research suggests that both the B and C assessments collectively provide a cost-effective and reliable two-step method for detecting early signs of environmental damage. This allows us to promptly implement measures,” says Wang.

The method can also be used to create a model that shows the impact of organic emissions on seabed ecosystems. 

This can help in planning a more sustainable development of the aquaculture industry.

The study shows that it is possible to detect early signs of damage in the environment. Here are Chun-Deng Wang and his superviser Yngvar Olsen.

References:

Wang, C.D. Data-Driven Assessment of Nutrient Flows and Benthic Environmental Impacts of Norwegian Salmon Cage Aquaculture, Doctoral thesis at NTNU, 2025.

Wang, C.D. & Olsen, Y. Monitoring regional benthic environment of Norwegian salmon cage farms, Aquaculture Environment Interactions, 2024. DOI: 10.3354/aei00474

Wang, C.D. & Olsen, Y. Quantifying regional feed utilization, production and nutrient waste emission of Norwegian salmon cage aquaculture, Aquaculture Environment Interactions, vol. 15, 2023. DOI: 10.3354/aei00463

———

Read the Norwegian version of this article on forskning.no

More content from NTNU:

ntnu partner fish farming the oceans environmental protection environment aquaculture
Powered by Labrador CMS