Mercury in Perch ( Perca fluviatilis ) from Sweden and Finland

High mercury concentrations in freshwater fish from the Nordic region have been of concern for a long time. Ongoing monitoring of key ecological species occurs in these countries to follow the situation. Here, we investigated spatial and temporal trends in mercury concentrations in European perch ( Perca fluviatilis ) within the Swedish and Finnish aquatic environments, collated from national monitoring programmes collected between 1974 and 2005 ( n = 5,172). Data were length and weight adjusted to remove perch size as a confounding factor. Temporal trend analyses and t tests comparing pre- and post-1996 mercury concentrations for each country (1974–1995; 1996–2005; perch adjusted to 200 g/25 cm), showed a significant decrease in mercury concentration in perch from Sweden ( p < 0.001) and a possible increase in mercury concentration in perch from Finland ( p < 0.001). No statistically significant geographical trends were seen. Average mercury concentrations exceeded both the current environmental quality standard (EQS) of 20 ng/g wet weight (ww) and a discussed EQS for the Nordic region of 200–250 ng/g ww. Despite large reductions in mercury use and production in these countries, concentrations in perch continue to be higher here than in other European areas, posing a continued environmental risk.