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Seabird mortality associated with ice trawlers in the Patagonian shelf: effect of discards on the occurrence of interactions with fishing gear

Authors

  • M. Favero,

    1. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
    2. Vertebrados, FCEyN, UNMDP, Mar del Plata, Argentina
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  • G. Blanco,

    1. Instituto Nacional de Investigación y Desarrollo Pesquero, Programa Observadores a Bordo, Mar del Plata, Argentina
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  • G. García,

    1. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
    2. Vertebrados, FCEyN, UNMDP, Mar del Plata, Argentina
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  • S. Copello,

    1. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
    2. Vertebrados, FCEyN, UNMDP, Mar del Plata, Argentina
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  • J. P. Seco Pon,

    1. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
    2. Vertebrados, FCEyN, UNMDP, Mar del Plata, Argentina
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  • E. Frere,

    1. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
    2. Universidad Nacional de la Patagonia Austral, Puerto Deseado, Santa Cruz, Argentina
    3. Wildlife Conservation Society, Wildlife Conservation Society, Bronx, NY, USA
    4. BirdLife International, Buenos Aires, Argentina
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  • F. Quintana,

    1. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
    2. Wildlife Conservation Society, Wildlife Conservation Society, Bronx, NY, USA
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  • P. Yorio,

    1. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
    2. Wildlife Conservation Society, Wildlife Conservation Society, Bronx, NY, USA
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  • F. Rabuffetti,

    1. Aves Argentinas, Programa Aves Marinas, Buenos Aires, Argentina
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  • G. Cañete,

    1. Fundación Viva Silvestre Argentina, Programa Marino, Mar del Plata, Argentina
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  • P. Gandini

    1. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
    2. Universidad Nacional de la Patagonia Austral, Puerto Deseado, Santa Cruz, Argentina
    3. Wildlife Conservation Society, Wildlife Conservation Society, Bronx, NY, USA
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  • Editor: T. Katzner

  • Associate Editor: M. Schaub

Correspondence
Marco Favero, Grupo Vertebrados, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata – CONICET, Funes 3250 (B7602AYJ) Mar del Plata, Argentina.
Email: marco.favero@acap.aq

Abstract

This study investigated the level of seabird mortality caused by the domestic trawl fleet (freshies) for hake (among other less important targets) operating in waters off central Patagonia (37–48°S), analyzing the effect of environmental and operational variability on the level of seabird interactions. With a total of 135 vessels, the fleet is one of the largest in Argentina. Specifically tasked seabird observers were placed onboard trawlers during the summer and winter seasons of the years 2006 and 2007. The type and number of seabird interactions (i.e. contacts with fishing gear) were recorded during shooting and hauling operations, covering 72 days of observation and 328 trawls. Black-browed albatrosses, white-chinned petrels Procellaria aequinoctialis, southern giant petrels Marconectes giganteus and southern royal albatrosses Diomedea epomophora were the most abundant species interacting with trawlers. Confirmed mortalities of black-browed and southern royal albatrosses were the result of collisions and entanglement with the warp cable while birds were scavenging. The estimated total mortality rate was 0.017 birds h−1 and 0.105 birds per vessel per day. The intensity of interactions (in terms of the number of contacts per unit time) was largely explained by the distribution of the fishing effort. Seasonality and the incidence of discards were the strongest factors explaining the occurrence of seabird interactions. The total annual mortality in the trawl fleet under investigation was roughly estimated to be from several hundred to over a thousand albatrosses. However, these figures should be considered preliminary due to the limited spatial and temporal coverage of data and the fact that estimations were based on a low number of observed mortalities. The implementation of a strategic discard management may significantly reduce the number of seabird mortalities from collisions with warp cables or improve the effectiveness of other complementary mitigation methods. Urgent implementation of mitigation measures is needed in this fleet to reduce the mortality of albatrosses and petrels along the Patagonian shelf.

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