Total and Methylmercury in Sardines Sardinella aurita and Sardina pilchardus from Tunisia

This paper reports concentrations of total mercury and methylmercury in muscle, liver and gonads of two sardines (Sardinella aurita, N=184 and Sardina pilchardus, N=87) from three coastal areas off Tunisia. Mercury concentration in muscle and liver showed significant positive correlation with fish length (i.e. with age). The relative methylmercury concentration was high and constant in muscle (>85% MeHg), and was decreasing with age in liver (from 50% to 20%), which might reflect the existence of a slow demethylation process. From the geographic point of view, Hg concentration was similar in the northern and eastern areas (0.32 μg g−1 dw in muscle for Sardinella aurita, 0.41 for Sardina pilchardus), but significantly lower in the southern zone (0.19 and 0.26, respectively, median values). Mercury concentration in the Tunisian sardines was twice to four times lower than in the northern Mediterranean Sea.