37-Year Study Reveals No Impact of Salmon Farming on Loch Nutrient Levels

Mowi Scotland has announced the results of a comprehensive 37-year independent water quality monitoring program, which found that salmon farming in freshwater lochs, specifically Loch Arkaig, has not altered the nutrient status of the water body.

Background of the Study

The research, conducted at Loch Arkaig where Mowi has farmed salmon for nearly four decades, comes in light of the company’s recent decision to cease operations at this location. The monitoring program began in 1987 and aimed to assess the ecological impact of salmon farming on water quality.

Key Findings

Stephen MacIntyre, Head of Environment at Mowi Scotland, stated:

“With the recent closure of our Loch Arkaig fish farm, it is only right to look back on our operations extending to almost 40 years, with a particular focus on the nutrient status of the water body, to better understand any potential impact from salmon farming.”

According to MacIntyre, the data spanning 37 years indicates that the geometric mean for phosphorus levels in Loch Arkaig has remained stable and within acceptable trophic levels. He emphasized that phosphorus is the primary nutrient regulating the loch’s nutrient status, with variations occurring throughout the year due to factors like land management and rainfall.

Water Quality Monitoring Techniques

Over the decades, regular water samples have been collected from Loch Arkaig by a dedicated team from the University of Stirling. These samples undergo laboratory analysis to evaluate the nutrient status of the loch, focusing on vital parameters such as total phosphorus (TP) and chlorophyll-a (Chl-a).

This continuous monitoring effort isn’t limited to Loch Arkaig; Mowi is also conducting similar assessments at its freshwater farms in Loch Ness, Loch Lochy, Loch Garry, Loch Shiel, and Loch Awe. The results are instrumental in monitoring the ecological health of these water bodies.

Mowi’s Commitment to Sustainable Practices

MacIntyre elaborated:

“Mowi’s continuous water quality monitoring program is another example of Mowi leading the Blue Revolution. We are committed to farming salmon sustainably and, in addition to complying with all regulatory standards and conservation thresholds, we often go beyond our regulatory requirements by carrying out additional environmental studies.”

The scope of these studies has been expanded following the latest requirements from the Aquaculture Stewardship Council, which introduced new water quality standards as part of its forthcoming Farm Standard. This long-term environmental data will provide unique scientific insights into freshwater ecosystems.

Conclusion and Future Prospects

The findings from this freshwater quality study come on the heels of Mowi’s groundbreaking research conducted in 2024, which evidenced seabed recovery at the former Isle of Ewe fish farm after the cessation of operations.

For more details on this study, visit the official source.

Images © Mowi