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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.

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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La pesquería del pez espada (Xiphias gladius Linnaeus, 1758) ha permitido tener acceso a una ictiofauna oceánica pelágica que en muchos casos es altamente migratoria. Estos peces son capturados como fauna concurrente y/o asociada a la mencionada pesquería, la cual ha sido escasamente estudiada y no se tiene real certeza de su composición taxonómica (Acuña et al. 2002). De ellos, se debe considerar el importante aporte de los peces condrictios, los cuales, según Acuña et al. (2002), alcanzan al 72% de la captura total y, por otra parte, es un grupo en el cual se ha puesto gran interés por su frágil estado en el ecosistema marino (Lamilla, 2005;Lamilla & Bustamante, 2005).De acuerdo a Pequeño (1989, 1997), en Chile se contabilizan 46 especies de tiburones distribuidos en seis órdenes y 13 familias, de estos el orden

Summary Feeding and stable isotope analyses for Bythaelurus canescens individuals were conducted to describe the diet of B. canescens as well as infer their potential prey species in the community. Stomach content analysis and mixing models by ratio isotopes composition were used to infer the food habits and calculate the trophic level of the dusky catshark, B. canescens. The results showed siphonophores and cephalopods as the most important food in the diet (67.9 and 20.2%, respectively). Calculated trophic level was 3.9, indicating that B. canescens is a meso‐predator in the upper continental slope communities off Chile. By mixing models based on isotope data it can be inferred that the probabilities of the consumption cephalopods and siphonophores would be 36.7 and 15.2%, respectively.

Se analizaron las ralaciones morfométricas de peces intermareales (Helcogrammoides chilensi, Helcogrammoides cunninghami, Scartichthys viridis e Hypsoblenius sordidus) que tienen una alta frecuencia como presas de depredadores tope de la misma área. Para las cuatro especies sed encontró una correlación positiva, la cual proporciona información para estudios posteriores de hábitos alimentarios.

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