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Ten replicates of wastewater were also collected in Plant C and D. Sludge samples were collected with ten replicates in all processing plants except Plant B. Sidestream materials (10 g) were provided by Plant A, B, and C with ten replicates and included residual raw materials of salmon such as cut-offs and guts (Plant A), broiler skin (Plant C), and pet feed ingredients made from salmon including fish meal and protein powder (Plant B). In sludge from the broiler processing plants, we detected a higher percentage of ARGs in classes of tetracycline including tet(Q), tet(E) and tet(A), and several MDR genes in sludge from Plant C. These findings highlight the need for waste treatment operators to consider the potential risk of AMR dissemination from sludge wastes. More than 99% of the ARGs detected in Plant A were also found in Plant C and D. This was unexpected since the production of salmon differs substantially from the broiler production but is likely explained by the large variety of ARGs detected in the broiler processing Plants C and D. More than 220 genes were also shared among Plant C and D, with approximately 110 unique genes detected in each plant. Differences in primary production, slaughter, processing conditions, and hygienic practices (Reiche et al., 2025) may explain the variation in ARG composition between Plant C and D. Most of the ARGs detected in the Norwegian Plant C belonged to classes of glycopeptides, beta-lactams and MLS, while beta-lactams, MDR and aminoglycoside classes dominated in the Romanian Plant D. A total of 114 high-risk genes were detected across the samples (Table 1), with differences observed between NFCF and FCS.