<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" style="font: inherit;"><H1 id=article-title-1><EM>PNAS</ABBR><SPAN class=slug-pub-date> May 19, 2009 </SPAN><SPAN class=slug-vol>vol. 106 </SPAN><SPAN class=slug-issue>no. 20 </SPAN><SPAN class=slug-pages>8245-8250 </SPAN></EM></H1>
<H1>Top marine predators track Lagrangian coherent structures</H1>
<DIV class=contributors>
<OL class=contributor-list id=contrib-group-1 jQuery1242788946296="61">
<LI id=contrib-1><SPAN class=name><A class=name-search href="http://www.pnas.org/search?author1=Emilie+Tew+Kai&sortspec=date&submit=Submit">Emilie Tew Kai</A></SPAN><A class=xref-aff id=xref-aff-1-1 href="http://www.pnas.org/content/106/20/8245.abstract?etoc#aff-1" jQuery1242788946296="63"><SUP>a</SUP></A><SPAN class=xref-sep>,</SPAN><A class=xref-corresp id=xref-corresp-1-1 href="http://www.pnas.org/content/106/20/8245.abstract?etoc#corresp-1"><SUP>1</SUP></A>,
<LI id=contrib-2><SPAN class=name><A class=name-search href="http://www.pnas.org/search?author1=Vincent+Rossi&sortspec=date&submit=Submit">Vincent Rossi</A></SPAN><A class=xref-aff id=xref-aff-2-1 href="http://www.pnas.org/content/106/20/8245.abstract?etoc#aff-2" jQuery1242788946296="64"><SUP>b</SUP></A>,
<LI id=contrib-3><SPAN class=name><A class=name-search href="http://www.pnas.org/search?author1=Joel+Sudre&sortspec=date&submit=Submit">Joel Sudre</A></SPAN><A class=xref-aff id=xref-aff-2-2 href="http://www.pnas.org/content/106/20/8245.abstract?etoc#aff-2" jQuery1242788946296="65"><SUP>b</SUP></A>,
<LI id=contrib-4><SPAN class=name><A class=name-search href="http://www.pnas.org/search?author1=Henri+Weimerskirch&sortspec=date&submit=Submit">Henri Weimerskirch</A></SPAN><A class=xref-aff id=xref-aff-3-1 href="http://www.pnas.org/content/106/20/8245.abstract?etoc#aff-3" jQuery1242788946296="66"><SUP>c</SUP></A>,
<LI id=contrib-5><SPAN class=name><A class=name-search href="http://www.pnas.org/search?author1=Cristobal+Lopez&sortspec=date&submit=Submit">Cristobal Lopez</A></SPAN><A class=xref-aff id=xref-aff-4-1 href="http://www.pnas.org/content/106/20/8245.abstract?etoc#aff-4" jQuery1242788946296="67"><SUP>d</SUP></A>,
<LI id=contrib-6><SPAN class=name><A class=name-search href="http://www.pnas.org/search?author1=Emilio+Hernandez-Garcia&sortspec=date&submit=Submit">Emilio Hernandez-Garcia</A></SPAN><A class=xref-aff id=xref-aff-4-2 href="http://www.pnas.org/content/106/20/8245.abstract?etoc#aff-4" jQuery1242788946296="68"><SUP>d</SUP></A>,
<LI id=contrib-7><SPAN class=name><A class=name-search href="http://www.pnas.org/search?author1=Francis+Marsac&sortspec=date&submit=Submit">Francis Marsac</A></SPAN><A class=xref-aff id=xref-aff-1-2 href="http://www.pnas.org/content/106/20/8245.abstract?etoc#aff-1" jQuery1242788946296="69"><SUP>a</SUP></A> and
<LI id=contrib-8><SPAN class=name><A class=name-search href="http://www.pnas.org/search?author1=Veronique+Gar%C3%A7on&sortspec=date&submit=Submit">Veronique Garçon</A></SPAN><A class=xref-aff id=xref-aff-2-3 href="http://www.pnas.org/content/106/20/8245.abstract?etoc#aff-2" jQuery1242788946296="70"><SUP>b</SUP></A> </LI></OL>
<P class=affiliation-list-reveal><A class=view-more href="http://www.pnas.org/content/106/20/8245.abstract?etoc#" jQuery1242788946296="62">-</A>Author Affiliations</DIV>
<OL class="affiliation-list showaffil" jQuery1242788946296="60">
<LI class=aff><A id=aff-1 name=aff-1></A>
<ADDRESS><SUP>a</SUP>Institut de Recherche pour le Développement, UR 109, Centre de Recherche Halieutique Méditerranéenne et Tropicale, 34203 Sète Cedex, France; </ADDRESS>
<LI class=aff><A id=aff-2 name=aff-2></A>
<ADDRESS><SUP>b</SUP>Laboratoire d'Etudes en Géophysique et Océanographie Spatiale, Centre National de la Recherche Scientifique, 31401 Toulouse Cedex 9, France; </ADDRESS>
<LI class=aff><A id=aff-3 name=aff-3></A>
<ADDRESS><SUP>c</SUP>Centre d'Etudes Biologiques de Chizé, Centre National de la Recherche Scientifique, 79360 Villiers en Bois, France; and </ADDRESS>
<LI class=aff><A id=aff-4 name=aff-4></A>
<ADDRESS><SUP>d</SUP>Instituto de Física Interdisciplinar y Sistemas Complejos, Consejo Superior de Investigaciones Cientificas–Universitat de les Illes Balears, E-07122 Palma de Mallorca, Spain </ADDRESS></LI></OL>
<OL class=fn-track>
<LI class=fn-edited-by id=fn-1>
<P id=p-1>Edited by David M. Karl, University of Hawaii, Honolulu, HI, and approved March 30, 2009 (received for review October 31, 2008) </DIV></LI></OL></DIV>
<DIV class="section abstract" id=abstract-1>
<H2>Abstract</H2>
<P id=p-4>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. </DIV></DIV>
<UL class=kwd-group>
<LI class=kwd><SPAN><A class=kwd-search href="http://www.pnas.org/search?fulltext=frigatebird&sortspec=date&submit=Submit&andorexactfulltext=phrase">frigatebird</A></SPAN>
<LI class=kwd><SPAN><A class=kwd-search href="http://www.pnas.org/search?fulltext=finite-size+Lyapunov+exponent&sortspec=date&submit=Submit&andorexactfulltext=phrase">finite-size Lyapunov exponent</A></SPAN>
<LI class=kwd><SPAN><A class=kwd-search href="http://www.pnas.org/search?fulltext=Mozambique+Channel&sortspec=date&submit=Submit&andorexactfulltext=phrase">Mozambique Channel</A></SPAN>
<LI class=kwd><SPAN><A class=kwd-search href="http://www.pnas.org/search?fulltext=submesoscale&sortspec=date&submit=Submit&andorexactfulltext=phrase">submesoscale</A></SPAN> </LI></UL>
<DIV class="section fn-group" id=fn-group-1>
<H2>Footnotes</H2>
<UL>
<LI class=corresp id=corresp-1><SUP>1</SUP>To whom correspondence should be addressed. E-mail: <A href="mailto:emilie.tewkai@ird.fr">emilie.tewkai@ird.fr</A> </LI></UL></DIV></td></tr></table><br>