Ecology, Status and Conservation of the White Shark, Carcharodon carcharias, in the Mediterranean Sea

Defense Date

7-2015

Document Type

Capstone

Degree Name

M.S. Marine Biology

First Advisor

Derek Burkholder

Second Advisor

Jeremy Kiszka

Third Advisor

Samuel Purkis

Abstract

The regular occurrence of the white shark, Carcharodon carcharias, in the Mediterranean Sea has been recorded since the Middle Ages (476-1453). Several studies have documented its presence throughout the basin, but only a few authors attempted to undertake a comprehensive study of this species at the scale of the Mediterranean Sea. With the addition of five new contemporary records along the coast of Sardinia (Italy) to the existing available data (sightings and catches), the number of reports of white sharks in the Mediterranean Sea has increased to 627 records, which range from the Middle Ages to 2013. The white shark appears to be more common in the western part of the Mediterranean Sea, in the Adriatic Sea and in the Sicilian Channel. Temporal analysis shows that white sharks are more frequently observed during summer months. All size classes have been recorded in the Mediterranean. However, the highest occurrence of young of the year has been recorded in the Sicilian Channel, in the Adriatic Sea and in the Aegean Sea. In the Mediterranean Sea the white shark exhibits a broad diet: the most common prey found included small cetaceans (Tursiops truncatus, Stenella coeruleoalba), tuna (Thunnus spp.), swordfish (Xiphias gladius) and loggerhead turtle (Caretta caretta). A total of 54 white shark records refer to an interaction with humans, which includes 43 bites and 11 reports of the presence of human remains in the stomach of captured animals. Analysis of temporal variation in mean lengths of white sharks found a decreasing trend from 1913 to 2012. The decreasing body size of great white sharks suggests this species is declining in the Mediterranean Sea. Urgent management decisions are currently needed to address this problem at international level.

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