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Assessing the Risk of Ships Striking Large Whales in Marine Spatial Planning

Authors

  • J. V. REDFERN,

    Corresponding author
    • Protected Resources Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, CA, U.S.A.
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  • M. F. MCKENNA,

    1. Marine Mammal Commission, Bethesda, MD, U.S.A.
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  • T. J. MOORE,

    1. Protected Resources Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, CA, U.S.A.
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  • J. CALAMBOKIDIS,

    1. Cascadia Research, Olympia, WA, U.S.A.
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  • M. L. DEANGELIS,

    1. Protected Resources Division, Southwest Regional Office, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Long Beach, CA, U.S.A.
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  • E. A. BECKER,

    1. Protected Resources Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Santa Cruz, CA, U.S.A.
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  • J. BARLOW,

    1. Protected Resources Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, CA, U.S.A.
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  • K. A. FORNEY,

    1. Protected Resources Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Santa Cruz, CA, U.S.A.
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  • P. C. FIEDLER,

    1. Protected Resources Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, CA, U.S.A.
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  • S. J. CHIVERS

    1. Protected Resources Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, CA, U.S.A.
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email jessica.redfern@noaa.gov

Abstract

Marine spatial planning provides a comprehensive framework for managing multiple uses of the marine environment and has the potential to minimize environmental impacts and reduce conflicts among users. Spatially explicit assessments of the risks to key marine species from human activities are a requirement of marine spatial planning. We assessed the risk of ships striking humpback (Megaptera novaeangliae), blue (Balaenoptera musculus), and fin (Balaenoptera physalus) whales in alternative shipping routes derived from patterns of shipping traffic off Southern California (U.S.A.). Specifically, we developed whale-habitat models and assumed ship-strike risk for the alternative shipping routes was proportional to the number of whales predicted by the models to occur within each route. This definition of risk assumes all ships travel within a single route. We also calculated risk assuming ships travel via multiple routes. We estimated the potential for conflict between shipping and other uses (military training and fishing) due to overlap with the routes. We also estimated the overlap between shipping routes and protected areas. The route with the lowest risk for humpback whales had the highest risk for fin whales and vice versa. Risk to both species may be ameliorated by creating a new route south of the northern Channel Islands and spreading traffic between this new route and the existing route in the Santa Barbara Channel. Creating a longer route may reduce the overlap between shipping and other uses by concentrating shipping traffic. Blue whales are distributed more evenly across our study area than humpback and fin whales; thus, risk could not be ameliorated by concentrating shipping traffic in any of the routes we considered. Reducing ship-strike risk for blue whales may be necessary because our estimate of the potential number of strikes suggests that they are likely to exceed allowable levels of anthropogenic impacts established under U.S. laws.

Evaluación del Riesgo de Colisiones de Barcos y Ballenas en la Planificación Marina Espacial

Resumen

La planificación marina espacial proporciona un marco de referencia integral para el manejo de usos múltiples del ambiente marino, y tiene el potencial para minimizar los efectos ambientales y reducir conflictos entre los usuarios. Las evaluaciones espacialmente explícitas de los riesgos para especies marinas clave derivados de las actividades humanas son un requerimiento de la planificación marina espacial. Evaluamos el riesgo de colisión de barcos con ballenas Megaptera novaeangliae, Balaenoptera musculus y B. physalus en rutas de navegación alternas derivadas de patrones del tráfico marino en el sur de California (U.S.A.). Específicamente, desarrollamos modelos del hábitat de ballenas y asumimos que el riesgo de colisión con barcos en las rutas alternativas fue proporcional al número de ballenas que los modelos pronosticaron que iban a ocurrir en cada ruta. Esta definición de riesgo asume que todos los barcos viajan en una sola ruta. También calculamos el riesgo asumiendo que los barcos viajan en rutas múltiples. Estimamos el potencial de conflictos entre la navegación y otros usos (entrenamiento militar y pesca) debido al traslape con las rutas. También estimamos el traslape entre rutas de navegación y áreas protegidas. La ruta con el menor riesgo para M. novaeangliae tenía el mayor riesgo para B. physalus y viceversa. El riesgo para ambas especies puede ser disminuido mediante la creación de una nueva ruta al sur de las Channel Islands y distribuyendo el tráfico entre esta ruta nueva y la existente en el Canal de Santa Bárbara. La creación de una ruta más larga puede reducir el traslape entre la navegación y otros usos al concentrar el tráfico de navegación. Las ballenas B. musculus se distribuyen más homogéneamente que M. novaeangliae y B. physalus en nuestra zona de estudio; por lo tanto, el riesgo no podría disminuir con la concentración del tráfico de navegación en ninguna de las rutas que consideramos. La reducción del riesgo de colisión de las ballenas puede ser necesario porque nuestra evaluación del número potencial de choques sugiere que es probable que excedan los niveles permisibles de impactos antropogénicos establecidos por las leyes de E.U.A.

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