Offshore fish farms show minimal environmental impact, say experts

One of Finland’s largest fish farms operates ten kilometres off the coast of Korsholm, a rare offshore facility in a country where most aquaculture takes place in sheltered coastal waters.

Markus Kankainen, a researcher at the Natural Resources Institute Finland, reports that measurements around offshore farms show no detectable environmental impact on water quality. While nutrient loading from fish waste does occur, it is so minimal that it does not affect water conditions, as offshore currents disperse it more effectively than in calm coastal areas.

Kankainen also notes no evidence of farmed fish spreading disease to wild populations in Finland.

Offshore farming does present challenges, however. Harsh weather and high waves can stress both fish and workers, with smaller fish requiring more protected conditions. Nets cover the pens to prevent fish from being blown out by storms and to deter predatory birds.

Ella Hellström, another researcher at the Natural Resources Institute, acknowledges that all food production has environmental costs, but emphasizes that aquaculture’s footprint has decreased significantly in recent decades. She stresses the need for ongoing research to further reduce impacts and improve fish welfare.

Matti Ovaska, a fisheries expert at WWF Finland, states that Finnish fish farms currently contribute only 1–2% of the country’s total phosphorus and nitrogen output. Yet he warns that doubling domestic fish consumption by 2035—a national target—would conflict with efforts to maintain healthy coastal waters, as increased production could strain ecosystems.

Finland currently relies on imports for about 80% of its fish consumption.