Debunking myths on Mediterranean great white sharks

(first posted on 1 Nov. 2010; adapted from an article appeared in Italian on La Rivista della Natura)

Towards the end of summer 2009 the welcome news arrived that great white sharks still exist in the Mediterranean. A newborn female, slightly longer than 1.5 m, sadly met her fate in the bottom of a trawl net. Fishermen from the island of Lampedusa reported the event to Simonpietro Canese, a researcher from ISPRA who was inventorying marine biodiversity in the Strait of Sicily.

It has been a while since the occurrence of the species in the region was in the news. The Mediterranean population of great white sharks, Carcharodon carcharias as it is known to scientists, is listed as Endangered in the Red List,

due to inferred significant reduction in numbers during the last decades. Although the reason(s) for decline is uncertain, the dismal conservation status of bluefin tuna, the sharks’ main prey in the region, is a likely candidate.

I don’t expect all readers to share my sense of elation, experienced in learning about the continued presence in our seas of the great predator. After all, there are not many species left on the planet which are able to devour a human being, and the great white shark is one of them. The perspective of being thorn to pieces by a sea monster still evokes in all of us an instinctive sense of horror; however in this case our instinct is unjustified, because in the Mediterranean there is little substance to the problem. This consideration provides me with the opportunity for trying to debunk some of the most common myths concerning the presence and dangerousness of great white sharks in the Mediterranean Sea.

Myth n. 1. Great whites enter the Mediterranean from the Atlantic through the Gibraltar Strait following ships. False. The Mediterranean hosts a resident population of these sharks, which are found in the region regularly (although in low densities), and breed here as well, as indicated most recently by the unlucky newborn from Lampedusa. By contrast, great white sharks are quite rare in the north-east Atlantic Ocean, so that in fact the exact opposite is more likely.

Myth n. 2. Great whites live in the open seas, and rarely come close to the coast. False. It is not on the basis of the distance from the coast, but on the basis of the presence of their prey that great white sharks decide where they want to be. In other seas, such as for instance off California, southern Australia and South Africa, these sharks are frequently found in few metres of water in front of rookeries of seals and sea lions, which are their main course in those locations. Significantly, great white sharks get occasionally caught in tuna traps (almadrabas or tonnare), which are laid along Mediterranean shores to intercept migrating bluefin tunas.

Myth n. 3. Great whites are a significant threat to Mediterranean swimmers. False. Please don’t get me wrong, there have been episodes in which a great white shark killed a human in the Mediterranean: to be exact, 21 cases in the entire basin in more than a century (1907-2010), i.e., 0.2 attacks per year on average, the last of which occurred 23 years ago in the bay of Baratti (near Livorno, Italy). A modest death toll indeed, compared for example with the tens of persons who die every year in Europe as a consequence of a bee sting. Casualties from shark attacks in the Mediterranean become even less significant considering every summer bathers in the Mediterranean waters number in the tens of millions.

This is a typical example of media bias: when a great white shark appears near our coasts it goes on TV right away, whereas nobody takes notice of the much more dangerous hornet.