Lake Maggiore is a southern subalpine lake located across the border between Italy and Switzerland. It is well studied since 1972 thanks to a monitoring program funded by the International Commission for the Protection of Italian-Swiss Waters (CIPAIS; https://www.cipais.org/web/). This program comprises the analysis of trace elements and persistent organic pollutants (POPs) in sediments of the lake and of the main tributaries and in different bioindicators: zooplankton, lake molluscs, riverine benthic invertebrates, and fish. This lake is characterized by legacy DDT and mercury contamination deriving from industrial activities. However, several different anthropogenic pressures act as potential sources of contamination. The present dataset (on excel file) consists of data regarding the analysis of mercury and POPs in three different species of fish - Rutilus rutilus, Alosa agone and Coregonus lavaretus – sampled seasonally in Lake Maggiore between 2022 and 2024. Analyses were performed on pools of caudal fillets of fish specimens with similar body size. The reported contaminant concentrations comprise: - Dichlorodiphenyltrichloroethane (DDT): 6 congeners and isomers (o,p' DDD, p,p' DDD, o,p' DDE, p,p' DDE, o,p' DDT and p,p' DDT) and total DDT. - Polychlorinated biphenyls (PCBs): 13 congeners (PCB-18, -28+31, -44, -52, -101, -138, -149, -153, -170, -180, -194, -209), and sumPCB13; - Polychlorinated biphenyls dioxin-like (PCBs-dl): 12 congeners (PCB-dl-77, -81, -126, -169, -105, -114, -118, -123, -156, -157, -167, -189) and sumPCB-dl; - Polybrominated diphenyl ethers (PBDEs): 8 congeners (BDE-28, -47, -99, -100, -153, -154, -183, -209) and sumBDE; - Hexabromocyclododecane (HBCD); - Decabromodiphenyl ethane (DBDPE); - Polycyclic musk fragrances (PMFs): ADBI (Celestolide), AHDI (Phantolide), HHCB (Galaxolide), AHTN (Tonalide), HHCB-L (Galaxolidone), and sumPMFs; - total mercury (THg) and methylmercury (MeHg); - lipidic content. The dataset allows for detecting changes in the concentrations over the analysed period, thus providing evidence for temporal variations of pollutants in the Lake and expected temporal trends of contamination (see annual reports on hazardous substances in Lake Maggiore at https://www.cipais.org/web/). Comparison between species can also provide a basis for identifying contamination pathways along the trophic chain and evaluation of risks for the ecosystem and for human health due to fish consumption. This research was funded by the International Commission for the Protection of Italian-Swiss Waters (CIPAIS), monitoring program 2022-2024 (https://www.cipais.org/web/).

The site Lago Maggiore-Italy (https://deims.org/f30007c4-8a6e-4f11-ab87-569db54638fe) belongs to the Long Term Ecological Research national and international networks (LTER-Italy, LTER-Europe and ILTER).