[OANNES Foro] Top marine predators track Lagrangian coherent structures

[raul sanchez]

PNAS May 19, 2009 vol. 106 no. 20 8245-8250 
Top marine predators track Lagrangian coherent structures


Emilie Tew Kaia,1, 
Vincent Rossib, 
Joel Sudreb, 
Henri Weimerskirchc, 
Cristobal Lopezd, 
Emilio Hernandez-Garciad, 
Francis Marsaca and 
Veronique Garçonb 
-Author Affiliations


aInstitut de Recherche pour le Développement, UR 109, Centre de Recherche Halieutique Méditerranéenne et Tropicale, 34203 Sète Cedex, France; 

bLaboratoire d'Etudes en Géophysique et Océanographie Spatiale, Centre National de la Recherche Scientifique, 31401 Toulouse Cedex 9, France; 

cCentre d'Etudes Biologiques de Chizé, Centre National de la Recherche Scientifique, 79360 Villiers en Bois, France; and 

dInstituto de Física Interdisciplinar y Sistemas Complejos, Consejo Superior de Investigaciones Cientificas–Universitat de les Illes Balears, E-07122 Palma de Mallorca, Spain 


Edited by David M. Karl, University of Hawaii, Honolulu, HI, and approved March 30, 2009 (received for review October 31, 2008) 

Abstract
Meso- and submesoscales (fronts, eddies, filaments) in surface ocean flow have a crucial influence on marine ecosystems. Their dynamics partly control the foraging behavior and the displacement of marine top predators (tuna, birds, turtles, and cetaceans). In this work we focus on the role of submesoscale structures in the Mozambique Channel in the distribution of a marine predator, the Great Frigatebird. Using a newly developed dynamic concept, the finite-size Lyapunov exponent (FSLE), we identified Lagrangian coherent structures (LCSs) present in the surface flow in the channel over a 2-month observation period (August and September 2003). By comparing seabird satellite positions with LCS locations, we demonstrate that frigatebirds track precisely these structures in the Mozambique Channel, providing the first evidence that a top predator is able to track these FSLE ridges to locate food patches. After comparing bird positions during long and short
 trips and different parts of these trips, we propose several hypotheses to understand how frigatebirds can follow these LCSs. The birds might use visual and/or olfactory cues and/or atmospheric current changes over the structures to move along these biologic corridors. The birds being often associated with tuna schools around foraging areas, a thorough comprehension of their foraging behavior and movement during the breeding season is crucial not only to seabird ecology but also to an appropriate ecosystemic approach to fisheries in the channel. 

frigatebird 
finite-size Lyapunov exponent 
Mozambique Channel 
submesoscale 

Footnotes

1To whom correspondence should be addressed. E-mail: emilie.tewkai en ird.fr 


      
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