Nutritional Decline in Farmed Salmon Raises Climate and Health Concerns

Farmed salmon, which now account for nearly 70 percent of global salmon consumption, may be losing the nutritional value that drove their market surge, according to reporting from Ars Technica.

New research conducted by USDA scientists shows a significant drop in the levels of heart-healthy Omega-3 fatty acids found in farmed salmon. This decline is attributed to a shift in diet; as smaller fish species were over-exploited, the industry moved toward land-based oils and crops, including canola and soy. In Norway, the world's largest producer, marine-based feed ingredients dropped from 90 percent in 1990 to approximately 23 percent by 2020, Ars Technica reports.

This dietary shift has created significant environmental trade-offs. Matthew Hayek, a researcher at New York University, states that soy consumption for all fish farming over the last two decades resulted in the clearing of forested land equivalent in size to Bangladesh or Nicaragua. Furthermore, advocacy groups in Norway found that 90 percent of the soy fed to their farmed salmon comes from three Brazilian companies sourcing from illegally deforested areas of the Amazon rainforest. Ars Technica also notes research showing that the move to crop-based ingredients doubled greenhouse gas emissions per kilogram of farmed fish in the U.K. and Europe between 2000 and 2020.

Laura Lee Cascada, director of the Aquaculture Accountability Project, describes the trend as trading marine exploitation for land exploitation. While the USDA has not yet changed its dietary guidelines—and the study's authors noted the sample size was not large enough to mandate a change—Cascada warns that consumers are left with a "wrong idea" of the nutrients they are receiving.