River and sea imprinting of toxic trace elements in Iberian wild Salmo salar. Implications for environmental health

Heavy metal pollution poses significant risks to aquatic ecosystems, wildlife, and human health. This is the first comprehensive assessment of toxic elements (As, Cd, Hg and Pb) in muscle of wild Atlantic salmon (Salmo salar) in a region with mining and industrial legacy at the south of its natural distribution (Asturias, northern Spain). In marine feeding grounds in Greenland these salmon are also exposed to heavy metal pollution. Wild juvenile and adult salmon were compared to determine the influence of local and global environmental conditions on heavy metal accumulation in this migratory species. Higher metal contribution during the marine stage, combined with marine imprinting for Hg, and river imprinting for As and Cd, show how these vulnerable populations are exposed to multiple pollution threats in their complex life cycle. Wild adults were more polluted than farmed S. salar from the North Sea and wild Oncorhynchus from the Pacific marketed in the region, especially for Cd, pointing at significant health risk from Bay of Biscay wild Atlantic salmon consumption.