Scientists reveal how great white sharks reached Mediterranean
The Herald November 17, 2010 | david ross IT came about through a wrong turn at sea 450,000 years ago.
Scottish scientists reveal today that great white sharks found in the Mediterranean were originally from Australia, but a navigational error – possibly by a few pregnant females during a time of global climate change – probably prompted them to turn east into the Med at Gibraltar. web site great white sharks
The sea’s peninsulas and narrow channels may also have made it difficult for the sharks to make their way back out.
The sharks have been found a few times in the Med: two were caught in the Bay of Edremit off Turkey two years ago; another off Tunisia in 2006; and another off Sicily 20 years ago.
Now there are fears for the future of the Med sharks, which are believed to be low in numbers and will not be replenished by immigration from the Atlantic. see here great white sharks
Scientists from Aberdeen University, in collaboration with colleagues in Plymouth, Istanbul and America, believe a combination of climatic factors and an unusually fast-flowing current, or eddy, called an Agulhas ring provides the best explanation why the female sharks ended up in the Med.
They think the Agulhas ring took the sharks up the west coast of Africa, despite their natural tendency to swim east to their birthing grounds around Australia.
However, when they entered the Atlantic, the west coast of Africa would have blocked eastward movement until they got to the Straits of Gibraltar, which took them east into the Med. Swordfish and bluefin tuna may also have arrived via these unusual currents, providing the founding white shark population with food.
The findings, published today in Proceedings of the Royal Society, were made after the team analysed the DNA of four great whites caught in the Med.
Dr Les Noble, a shark geneticist from Aberdeen’s school of biological sciences, said: “We were absolutely astonished.
“We looked at the DNA signature of the sharks and found they were all from the same extended family.” david ross
