Farmed Salmon Omega-3 Levels Drop as Industry Shifts to Land-Based Feed

Farmed salmon are becoming significantly less nutritious as the industry replaces marine-based feed with terrestrial crops. New research led by USDA scientists indicates that Omega-3 fatty acid levels in these fish have dropped considerably, threatening the health benefits consumers expect from the protein.

The decline is driven by a fundamental shift in what salmon are fed. In Norway, for example, marine-based feed ingredients plummeted from 90 percent in 1990 to approximately 23 percent by 2020. To sustain massive production growth, the industry has pivoted toward land-based crops, specifically soy and canola. This dietary transition comes as farmed salmon production tripled between 2000 and 2020, with farmed fish now accounting for nearly 70 percent of all salmon consumed globally.

The Drive for Scale

This industrial pivot was born from a surge in global demand, fueled largely by dietary guidelines that recommend fatty fish for heart health. As the industry expanded, it faced a critical shortage of the small fish species traditionally used in feed, which were being over-exploited. To keep pace with the tripling of production, aquaculture firms shifted to terrestrial agriculture to provide the necessary bulk and calories for their stocks.

Implications for Public Health

The nutritional fallout of this shift is significant. Because Omega-3s are derived from the marine environment, the reliance on soy and canola has diluted the final product. This suggests that current national dietary guidelines may be outdated, as consumers eating farmed salmon may not be receiving the cardiovascular benefits they believe they are.

"So in the meantime, it’s going to stay the same and people will have this wrong idea of how much Omegas they’re getting," said Laura Lee Cascada, director of the Aquaculture Accountability Project.

Environmental Trade-offs

Beyond the dinner plate, the shift has created a new set of ecological pressures. By moving away from marine-based feeds, the industry has reduced some pressure on wild forage fish but increased its reliance on industrial monocultures.

According to Cascada, the industry is essentially "trading one problem—marine exploitation—for another—land exploitation." This transition links the aquaculture industry directly to terrestrial environmental degradation, including the expansion of crop land into sensitive ecosystems.

What Remains Unclear

While the nutritional decline is documented, the full scale of the environmental cost remains a subject of ongoing scrutiny. Researchers continue to investigate the precise correlation between crop-based feed and specific greenhouse gas emission increases, as well as the exact acreage of deforestation linked to aquaculture soy. For now, the data confirms a clear trend: the salmon of today is not the same fish as the salmon of thirty years ago.