According to data obtained in this work, and as described in the literature, the concentrations of MeHgþ are higher in fish than shellfish being predatory fish those samples showing the highest values.Higher MeHgþ content in fish samples could be related to the fat content. Methylmercury is a fat-soluble substance and therefore can be accumulated in the fatty tissues more easily than inorganic mercury. Bluefish samples, such as salmon and tuna with high fat content, present high levels of MeHgþ.Whitefish and shellfish, with lower fat content, present lower MeHg þ concentration and in the case of some shellfish samples the predominant mercury species is iHg