Metal(loid)s in mesopelagic fishes from the Mediterranean food web

In the present study, concentrations of different metal(loid)s (As, Cd, Cr, Hg, Ni and Pb) were measured in Mediterranean mesopelagic fish species belonging to the families Gonostomatidae, Microstomatidae, Myctophidae, Paralepididae, Phosichthyidae, Sternoptychidae, and Stomiidae. These fish species represent key prey for top pelagic predators of high commercial value, such as tuna and swordfish, representing not only a relevant but neglected source of metal(loid)s from lower to higher trophic concentrations, but also potential vectors for the trophic transfer of some contaminants, though not necessarily via biomagnification. Different concentrations of As (mean range of 0.350-5.707 μg/g), Cd (mean range of 0.181-0.813 μg/g), Cr (mean range of 0.148-2.680 μg/g), Hg (mean range of 0.026-0.456 μg/g), Ni (mean range of 0.112-2.643 μg/g) and Pb (mean range of 0.076-2.492 μg/g) were determined among the species, likely reflecting variations in their feeding behaviour and ecology. Concentrations of Cd and Pb in some species exceeded the European regulatory limits for fishery products, whereas Hg concentrations remained below legal thresholds, and As, Cr, and Ni are currently not regulated. Although these species are not of high commercial value, their role as prey for large pelagic predators of economic interest highlights the need for such studies in a broader perspective of environmental monitoring and risk assessment, aimed at supporting sustainable management strategies of marine resources and ensuring high standards of food safety.