Annual re-sightings of photographically identified white sharks (Carcharodon carcharias) at an eastern Pacific aggregation site (Guadalupe Island, Mexico) (original) (raw)

Abstract

A systematic, reliable method for identifying white sharks, Carcharodon carcharias Linnaeus, from underwater photographs was developed and applied to examine site fidelity at Guadalupe Island, Mexico (29˚N, 118˚W). The most reliable features for repeat identification in multiple years were the pigment patterns on the gill flaps, pelvic fins, and caudal fins. Pigment patterns in all three regions were asymmetrical on the right and left sides making it necessary to photograph both sides to catalog each individual. However, once cataloged, an individual could be re-identified using a partial body image. Using this method, 73 individuals were identified between 2001 and 2005. Site fidelity was indicated through repeated annual sightings of individuals with 78% of the identified sharks observed over at least 2 years. Males were found to arrive at Guadalupe Island as early as July and females in September. Peak abundances at the site occurred August–December. The sex ratio was not significantly different from unity in 2002, 2004, and 2005. This monitoring technique has shown Guadalupe Island to be an important white shark aggregation site in the eastern Pacific.

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Acknowledgments

We would like to thank Tom Pfleger whose field assistance, interest and funding made this project possible. We would like to acknowledge the help of Jessica Harper whose interest and persistence in tracking photographs of white sharks helped give this project momentum, Patric Douglas and Lawrence Growth for access to their photographs and videos, and Steve Drogin for allowing us to use his shark cage. This project was funded by a grant through the George T. Pfleger Foundation. We would like to acknowledge all photographers whose photographs were used in our database, namely Scott Aalbers, Paul Adie, Tony Baskeyfield, Chris Bouton, Eric Cheng, Phil Colla, Luke Cresswell, Robin Criman, Dean Cross, Jonathan Gershon, Mark Grindley, Dave Haas, Tim Harris, Guy Harvey, Jeff Hoover, Bill James, Chris Limon, Andy Lineseisen, Keith Ludwig, James MacIntosh, Chris Marshall, Jay Marzolf, Antonio Mondragon, Bonnie Pelnar, Doug Perrine, Daniel Preston, Jeff Prevet, Simon Rogerson, Toshimi Sakurai, Chugey Sepulveda, Phil Streather, Mike Urciuoli, Bery Wells, Rick Westphal, Chris Zacharias, and Phil Zerofski. We thank Dr. Felipe Galván Magaña for Mexican permitting assistance. All research was conducted in accordance with permits through Centro Interdisciplinario de Ciencias Marinas Instituto Politecnico Nacional.

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Authors and Affiliations

  1. Pfleger Institute of Environmental Research, Oceanside, CA, 92054, USA
    Michael L. Domeier & Nicole Nasby-Lucas

Authors

  1. Michael L. Domeier
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  2. Nicole Nasby-Lucas
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Correspondence toMichael L. Domeier.

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Communicated by J.P. Grassle, New Brunswick

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Domeier, M.L., Nasby-Lucas, N. Annual re-sightings of photographically identified white sharks (Carcharodon carcharias) at an eastern Pacific aggregation site (Guadalupe Island, Mexico).Mar Biol 150, 977–984 (2007). https://doi.org/10.1007/s00227-006-0380-7

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