Elemental accumulation in three mesopelagic fishes from the strait of Messina (Central Mediterranean Sea)

Mesopelagic fishes are key mediators of energy and contaminant transfer between epipelagic and deep-pelagic layers, yet species-specific inorganic element data remain scarce for non-commercial taxa. This study quantifies nutritional elements and trace metals in three esopelagic fishes from the Strait of Messina (Central Mediterranean Sea): Hygophum benoiti, Argyropelecus hemigymnus and Macroramphosus gracilis. Specimens stranded along the Capo Peloro coastline were measured for standard length and wet weight, pooled by species, and analysed as whole fish using microwave digestion followed by ICP-MS, ICP-OES and DMA-80 to determine 18 inorganic elements (Ca, K, Na, Mg, Fe, Zn, Cu, Se, Mn, Cd, Pb, As, Hg, Cr, Ni, Sn, Sb, Co). All three species exhibited favourable mineral profiles, with particularly high concentrations of Ca, Fe, Zn and Se, and Se:Hg molar ratios consistently greater than 1, indicating a high nutritional potential and a likely mitigation of mercury-related risk. Mercury and lead concentrations were uniformly low (Hg ≈0.01–0.02 mg kg1; Pb ≤0.09 mg kg-1 wet weight), remaining far below current European regulatory limits for fishery products. Total arsenic ranged from ~1.0 to 2.1 mg kg-1, within the broad intervals reported for mesopelagic micronekton, and was dominated by non-toxic organic forms according to inorganic As estimates. Cadmium showed the clearest interspecific differences, with M. gracilis reaching mean values around 0.18 mg kg-1, close to the upper EU guideline range, whereas A. hemigymnus and H. benoiti displayed lower means. Overall, these results provide the first integrated nutritional and contaminant assessment for these three mesopelagic fishes, highlighting their role as both vectors of trace elements and potentially valuable, though currently unexploited, small-fish resources in the central Mediterranean Sea.