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Abstract.-The diet of the blue shark Prionace glauca off central and northern Chile in the eastern South Pacific, during 2005 and 2006 were dominated by teleost fishes (72.21 %IRI) and cephalopods (27.07 %IRI). The seasonal feeding of blue shark showed as the most important prey diverse teleost fish species. Our findings would confirm that blue shark is a predator with wide trophic spectrum in the eastern south Pacific, although a higher number of stomachs need to be studied.

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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.

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