Great white shark attacks

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Using Stable Isotope Analysis to Understand the Migration and Trophic Ecology of Northeastern Pacific White Sharks (Carcharodon carcharias)
Aaron B. Carlisle1*, Sora L. Kim2, Brice X. Semmens3, Daniel J. Madigan1, Salvador J. Jorgensen1,4, Christopher R. Perle1, Scot D. Anderson5, Taylor K. Chapple6,7, Paul E. Kanive8, Barbara A. Block1
1 Hopkins Marine Station of Stanford University, PacificGrove, California, United States of America, 2 University of California Santa Cruz, Santa Cruz, California, United States of America, 3 Scripps Institute of Oceanography, University of California San Diego, San Diego, California, United States of America, 4 Monterey Bay Aquarium, Monterey, California, United States of America, 5 Point Reyes National Seashore, Inverness, California, United States ofAmerica, 6 University of California Davis, Davis, ¨ California, United States of America, 7 Max-Planck-Institut fur Ornithologie, Radolfzell, Germany, 8 Montana State University, Bozeman, Montana, United States of America

The white shark (Carcharodon carcharias) is a wide-ranging apex predator in the northeastern Pacific (NEP). Electronic tagging has demonstrated that white sharksexhibit a regular migratory pattern, occurring at coastal sites during the late summer, autumn and early winter and moving offshore to oceanic habitats during the remainder of the year, although the purpose of these migrations remains unclear. The purpose of this study was to use stable isotope analysis (SIA) to provide insight into the trophic ecology and migratory behaviors of white sharks in theNEP. Between 2006 and 2009, 53 white sharks were biopsied in central California to obtain dermal and muscle tissues, which were analyzed for stable isotope values of carbon (d13C) and nitrogen (d15N). We developed a mixing model that directly incorporates movement data and tissue incorporation (turnover) rates to better estimate the relative importance of different focal areas to white shark dietand elucidate their migratory behavior. Mixing model results for muscle showed a relatively equal dietary contribution from coastal and offshore regions, indicating that white sharks forage in both areas. However, model results indicated that sharks foraged at a higher relative rate in coastal habitats. There was a negative relationship between shark length and muscle d13C and d15N values, whichmay indicate ontogenetic changes in habitat use related to onset of maturity. The isotopic composition of dermal tissue was consistent with a more rapid incorporation rate than muscle and may represent more recent foraging. Low offshore consumption rates suggest that it is unlikely that foraging is the primary purpose of the offshore migrations. These results demonstrate how SIA can provide insightinto the trophic ecology and migratory behavior of marine predators, especially when coupled with electronic tagging data.
Citation: Carlisle AB, Kim SL, Semmens BX, Madigan DJ, Jorgensen SJ, et al. (2012) Using Stable Isotope Analysis to Understand the Migration and Trophic Ecology of Northeastern Pacific White Sharks (Carcharodon carcharias). PLoS ONE 7(2): e30492.doi:10.1371/journal.pone.0030492 Editor: Tamara Natasha Romanuk, Dalhousie University, Canada Received November 1, 2010; Accepted December 18, 2011; Published February 15, 2012 Copyright: ß 2012 Carlisle et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author andsource are credited. Funding: Funding was provided by the Alfred P. Sloan Foundation, the David and Lucile Packard Foundation, the Gordon and Betty Moore Foundation, Monterey Bay Aquarium Foundation, the Office of Naval Research, and Stanford University’s School of Humanities and Sciences. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of...