Levels of environmental pollutants in flounder (Platichthys flesus L.) and cod (Gadus morhua L.) caught in the waterway of Glomma, Norway. II. Mercury and arsenic.

The present study is a survey on mercury and arsenic pollution in two sedentary fish species stationed in or close to the Glomma estuary in the Hvaler archipelago, Norway. Mercury and arsenic were determined individually in 80 flounder (Platichthys flesus L.) and 100 cod (Gadus morhua L.). The fish were caught at five different localities near or in the relatively polluted Glomma estuary. There were significantly higher mercury and arsenic concentrations in fillets of flounder than in fillets of cod (wet weight), 0.15 vs. 0.08 mg/kg and 5.2 vs. 4.1 mg/kg, respectively. Seasonal variation in mercury concentration was only found in flounder, with a significantly higher level in spring than in autumn. A significant increase in mercury content with increasing age was found for both species. For cod, a significantly higher arsenic level was found on the outer stations as compared to the inner stations, while arsenic levels in flounder was less dependent on sampling site.