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Marine Ecology Progress Series

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MEPS 424:237-246 (2011)  -  DOI:

Yo-yo vertical movements suggest a foraging strategy for tiger sharks Galeocerdo cuvier

Itsumi Nakamura1,*, Yuuki Y. Watanabe2, Yannis P. Papastamatiou3, Katsufumi Sato1, Carl G. Meyer4

1International Coastal Research Center, Atmosphere and Ocean Research Institute, University of Tokyo, 2-106-1 Akahama, Otsuchi, Iwate 028-1102, Japan
2National Institute of Polar Research, 10-3 Midori-cho, Tachikawa, Tokyo 190-8518, Japan
3Florida Museum of Natural History, University of Florida, 280 Dickinson Hall, Museum Road, Gainesville, Florida 32611, USA
4Hawaii Institute of Marine Biology, University of Hawaii at Manoa, PO Box 1346, Kaneohe, Hawaii 96744, USA

ABSTRACT: Many pelagic fishes exhibit ‘yo-yo’ diving behavior, which may serve several possible functions, including energy conservation, prey searching and navigation. We deployed accelerometers and digital still cameras on 4 free-ranging tiger sharks Galeocerdo cuvier, to test whether their vertical movements are most consistent with energy conservation or prey searching. All sharks swam continuously, with frequent vertical movements through the water column at mean swimming speeds of 0.5 to 0.9 m s–1. Tail-beating was continuous except for sporadic, powerless gliding during descents (from 0 to 18% of total descent time). At a given tailbeat frequency, swimming speeds were lower during ascent than descent (consistent with negative buoyancy). Burst swimming events, which might represent prey pursuits, were observed during all phases of vertical movements. Camera images showed a variety of potential prey and the possible capture of a unicornfish. Collectively, results suggest that yo-yo diving by tiger sharks is not primarily for energy conservation, but probably represents an effective search strategy for locating prey throughout the water column.

KEY WORDS: Tiger shark · Marine top predator · Swimming behavior · Swim speed · Stroke frequency · Foraging · Bio-logging · Data logger

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Cite this article as: Nakamura I, Watanabe YY, Papastamatiou YP, Sato K, Meyer CG (2011) Yo-yo vertical movements suggest a foraging strategy for tiger sharks Galeocerdo cuvier. Mar Ecol Prog Ser 424:237-246.

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