Fish farming least harmful in northern Norway

A recent study on the environmental conditions around fish farms reveals a surprising trend: Environmental conditions on the seabed around fish farms generally improve the farther north you go in Norway.

The researchers have focused on how efficiently the feed is used, how much nutrient waste fish farming releases into the marine environment, and how life on the seabed changes.

“Our results show a significant geographical variation in both feed utilization and nutrient emissions. Efficiency increases steadily from south to north in Norway,” said Chun-Deng Wang from Norwegian University of Science and Technology (NTNU’s) Department of Biology.

He carried out the research as 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 said.

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 carried out 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. His supervisor was Yngvar Olsen from Trondhjem Biological Station (TBS) in Ilsvika. You can see a website that describes his research here.

Why does the seabed in the north fare better?

It turns out that the north fares best in this study, and this is most likely closely related to water temperature and other physical conditions in the environment.

“Benthic conditions are strongly influenced by feed utilization, water depth, biomass density and the length of the production cycle,” explained Chun-Deng Wang.

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 said.

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, there are a number of problems related to factors such as escaped fish, pollution and unsustainable feed sourcing.

However, this study brings good news; its findings show that benthic ecosystems can recover quickly, especially when damage is detected early.

It is also clear that the more comprehensive C assessment 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, enabling us to promptly implement measures,” said Chun-Deng Wang.

The method can also be used to create a model that shows the impact of organic emissions on benthic ecosystems. This can help in planning a more sustainable development of the aquaculture industry.

References:Wang CD., & Olsen Y. (2023). Quantifying Regional Feed Utilization, Production and Nutrient Waste Emission of Norwegian Salmon Cage Aquaculture. AEI 15:231-249. https://doi.org/10.3354/aei00463

Wang CD., & Olsen Y. (2024). Monitoring Regional benthic environment of Norwegian Salmon Cage Farms. AEI 16:71-90. https://doi.org/10.3354/aei00474