Mercury levels in myliobatid stingrays (Batoidea) from the Gulf of California: tissue distribution and health risk assessment

O. Escobar-Sánchez, J. Ruelas-Inzunza, J. C. Patrón-Gómez, D. Corro-Espinosa

With the aim of knowing Hg distribution in selected tissues of myliobatid stingrays and assessing health risk to Mexican population, Hg concentration was determined in the muscle and liver of four ray species. Total Hg levels were determined by cold vapor atomic absorption spectrophotometry. With respect to the muscle, devil rays (Mobula spp.) showed lower Hg levels (<0.22 μg g(-1)) than Rhinoptera steindachneri (0.37 ± 0.25 μg g(-1) wet weight). In the case of the liver, the highest Hg concentration was found in Mobula japanica (0.22 ± 0.01 μg g(-1)). Hg levels in the muscle and liver varied according to the species; in some case, the liver accumulated more Hg than the muscle and the opposite pattern in other cases. R. steindachneri showed a significant difference between both tissues. No significant differences of Hg levels between males and females and between juveniles and adult specimens of R. steindachneri were found. Positive correlation between Hg concentrations and disc width and total weight was not significant for R. steindachneri (Rs < 0.36, p > 0.05). Batoids showed Hg values below the Mexican (NOM-027-SSA1-1993) limits (1.0 μg g(-1)) in fishes for human consumption. The species with the highest potential of Hg transfer to human population is R. steindachneri; however, an adult (70 kg) could consume approximately 943 g per week without representing a health risk. Nevertheless, further and continuous monitoring is needed since batoids support an important fishery in Mexican waters, being a food resource and income to coastal communities.