Heavy metal concentrations of two highly migratory sharks (Prionace glauca and Isurus oxyrinchus) in the southeastern Pacific waters: Comments on public health and conservation

Despite the importance of sharks in structuring the marine food web, their biomass is declining dramatically throughout the world ́s oceans due to fishing pressures. Sharks caught as by-catch in long-line fisheries are sold for shark fins in the Asian fish market and secondarily as trunk sales for local consumption and fish meal. In order to determine the levels of heavy metals (mercury and lead) in oceanic shark populations in South Pacific waters, analyses of 39 Prionace glauca and 69 Isurus oxyrinchus were conducted. Mercury (Hg) and lead (Pb) were measured by cold vapor and via acetylene flame techniques, respectively. Mercury concentrations were similar in the studied sharks (p=0.1516), with 0.048 ± 0.03 μg·g^-1 w/w for P. glauca and 0.034 ± 0.023 μg·g^-1 w/w for I. oxyrinchus. P. glauca showed greater values of lead than I. oxyrinchus (p<0.001). Large specimens of both species showed high heavy metal concentration, while sexes showed no statistical differences (p>0.05). The metal concentrations reported in this work constitute a risk for human health, mainly from the high contributions of lead in tissues of P. glauca and I. oxyrinchus.