Residency of the scalloped hammerhead shark (<Emphasis Type="Italic">Sphyrna lewini</Emphasis>) at Malpelo Island and evidence of migration to other islands in the Eastern Tropical Pacific |
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Authors: | Sandra?Bessudo Email author" target="_blank">German?Andres?SolerEmail author A?Peter?Klimley James?T?Ketchum Alex?Hearn Randall?Arauz |
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Institution: | 1.Fundación Malpelo,Bogotá,Colombia;2.Biotelemetry Laboratory,University of California, Davis,Davis,USA;3.PRETOMA,San Jose,Costa Rica;4.Charles Darwin Foundation,Puerto Ayora,Ecuador |
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Abstract: | Sixty nine hammerhead sharks, Sphyrna lewini, were tagged at Malpelo Island (Colombia) with ultrasonic transmitters during March 2006, 2007 and 2008, as part of a study
to understand their residency at the island and their horizontal and vertical movements. Five sharks visited Cocos Island,
627 km distant from Malpelo. One of the sharks that appeared at Cocos Island also visited the Galapagos Islands, 710 km from
Cocos, a month later. There is connectivity of Sphyrna lewini between Malpelo, Cocos and the Galapagos Islands, but the frequency of movements between the islands appears to be relatively
low (<7% of the tagged sharks). The most common depth at which the sharks swam coincided with the thermocline (rs = 0.72, p < 0.01). The depth of the thermocline varied depending on the time of the year. Nocturnal detections of the sharks were more
frequent during the cold season than during the warm season (W = 60, p < 0.01). We also found that hammerheads spent significantly more time on the up-current side of the island (Kruskal-Wallis = 31.1008;
p < 0.01). This study contributes to the knowledge of hammerhead sharks not only in Malpelo Island but also at a regional level
in the Eastern Tropical Pacific. |
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