Spanish scientists have reported a ten-fold increase in the number of sharks spotted off popular tourist beaches in north eastern Spain.
At least 20 sharks were recorded in Mediterranean waters off the Catalan coast last year, a figure that far exceeded previous years.
In 2003 three were seen, in 2004 five were reported and in 2005 and 2006 only two of the fish were found each year.
A report published by the Foundation for the Conservation and Rehabilitation of Marine Animals (CRAM) revealed that among the unusual visitors to the area were a hammerhead shark and several sandbar sharks, one of which was caught and transferred to Barcelona Aquarium last August where it died several days later.
Although there were no reported attacks on bathers, the hammerhead shark (Sphyrna zygaena) , which can grow to four metres, is said to be potentially dangerous to humans.
Four basking sharks were also spotted in the region. The harmless fish can grow to over 12 metres and are common in the Mediterranean, but are not usually found so close to shore.
There has also been an increasing number of giant rays recorded in waters off north eastern Spain.
The authors of the report were at a loss to explain why so many sharks and rays had found their way into northern Mediterranean waters when their usual habitat was to the east and south.
“Although the appearance of some of the species can be regarded as rare or exceptional there is insufficient data to establish a relationship between events and changes in weather patterns,” the report said.
But scientists have in the past suggested that warmer waters and altering marine currents caused by climate change are in part to blame for a shift in species behaviour in the region.
One such change is the now regular invasion of jellyfish that plague Spanish beaches each summer.