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Transequatorial Migrations by Basking Sharks in the Western Atlantic Ocean

2009; Elsevier BV; Volume: 19; Issue: 12 Linguagem: Inglês

10.1016/j.cub.2009.04.019

1879-0445

Gregory B. Skomal, Stephen I. Zeeman, John Chisholm, Erin L Summers, Harvey J. Walsh, Kelton W. McMahon, Simon R. Thorrold,

Marine animal studies overview

The world's second largest fish, the basking shark (Cetorhinus maximus), is broadly distributed in boreal to warm temperate latitudes of the Atlantic and Pacific oceans from shallow coastal waters to the open ocean [1Compagno L.J.V. Bullhead, Mackerel and Carpet Sharks (Heterodontiformes, Lamniformes and Orectolobiformes).Sharks of the World: An Annotated and Illustrated Catalogue of Shark Species Known to Date. Volume 2. FAO, Rome2001Google Scholar, 2Francis M.P. Duffy C. Distribution, seasonal abundance and bycatch of basking sharks (Cetorhinus maximus) in New Zealand, with observations on their winter habitat.Mar. Biol. 2002; 140: 831-842Crossref Scopus (32) Google Scholar]. Previous satellite archival tagging in the North Atlantic has shown that basking sharks move seasonally, are often associated with productive frontal zones [3Sims D.W. Southall E.J. Richardson A.J. Reid P.C. Metcalfe J.D. Seasonal movements and behaviour of basking sharks from archival tagging: no evidence of winter hibernation.Mar. Ecol. Prog. Ser. 2003; 248: 187-196Crossref Scopus (170) Google Scholar, 4Skomal G.B. Wood G. Caloyianis N. Archival tagging of a basking shark, Cetorhinus maximus, in the western North Atlantic.J. Mar. Biolog. Assoc. U. K. 2004; 84: 795-799Crossref Scopus (29) Google Scholar], and may make occasional dives to mesopelagic depths [3Sims D.W. Southall E.J. Richardson A.J. Reid P.C. Metcalfe J.D. Seasonal movements and behaviour of basking sharks from archival tagging: no evidence of winter hibernation.Mar. Ecol. Prog. Ser. 2003; 248: 187-196Crossref Scopus (170) Google Scholar, 5Gore M.A. Rowat D. Hall J. Gell F.R. Ormond R.F. Transatlantic migration and deep mid-ocean diving by basking shark.Biol. Lett. 2008; 4: 395-398Crossref PubMed Scopus (67) Google Scholar]. However, basking sharks are thought to be restricted to temperate latitudes, and the extent to which they exploit deeper-water habitat remains enigmatic. Via satellite archival tags and a novel geolocation technique, we demonstrate here that basking sharks are seasonal migrants to mesopelagic tropical waters. Tagged sharks moved from temperate feeding areas off the coast of southern New England to the Bahamas, the Caribbean Sea, and onward to the coast of South America and into the Southern Hemisphere. When in these areas, basking sharks descended to mesopelagic depths and in some cases remained there for weeks to months at a time. Our results demonstrate that tropical waters are not a barrier to migratory connectivity for basking shark populations and highlight the need for global conservation efforts throughout the species range.