This study investigated the amount of mercury (Hg) found in Eurasian otters (Lutra lutra) from Denmark in 2011-2019. The Hg concentrations were determined in liver and fur, and the age and the sex of the individual otters were determined. The stable isotope imprint of 13C and 15N in muscle tissue was used to determine the habitat and the trophic position, respectively. The linear correlations among the variables were determined, and an analysis of variance was conducted among age groups, males and females. A general linear modelling approach was used in order to determine the influence of age, sex, habitat and trophic position towards Hg exposure.
The results show that the current Hg residues in the samples are generally low, thereby posing low or no threat of clinical Hg toxicity towards the Danish population of otters. However, a significant proportion of the Hg concentrations found in liver tissue exceed the LOEL of 3.4 mg kg-1 (ww, liver) where changes in CNS biomarkers have been described.
The GLM indicates that the Hg concentrations in liver and fur are best described by the age of the individual otters and the foraging habitat. In general, the Hg concentrations increase with age and towards freshwater environments. No statistically significant difference was detected between males and females.