In a paper published today, an international team of researchers, led by the University of Aberdeen, reveal that sharks have failed to colonise at depths greater than 3,000 metres.

Sharks occur throughout the world's oceans and it had been hoped that as man explores deeper into the abyss and beyond throughout the largest environment on the planet - new species would be discovered.

However, 20 years of exploration, combined with analysis of records over the past 150 years, has convinced the team of scientists that the world's oceans are 70% shark-free. Their findings are published in Proceedings of The Royal Society, Biological Series.

The average depth of the oceans is 4,000m and bony fishes - relatives of cod - thrive down to around 9,000m depth. Scientists do not know why sharks are absent from the deep but suggest one possible reason could be due to lack of food.

They warn their finding has environmental implications.

Professor Monty Priede, Director of Oceanlab at the University of Aberdeen, said: "Sharks are apparently confined to around 30% of the world's oceans, and all populations are therefore within reach of human fisheries, near the surface and at the edges of deep water, around islands, seamounts and the continents.

"Sharks are already threatened worldwide by the intensity of fishing activity but our finding suggests they may be more vulnerable to over-exploitation than was previously thought."

The scientists based their conclusions on a wide range of data which includes information gathered during a major month long expedition along the Mid-Atlantic Ridge between Iceland and the Azores in 2004.

More than 100 scientists from over 16 countries were involved in the MAR-ECO project which is part of the 10-year Census of Marine Life programme which is exploring the abundance, di
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Contact: Jennifer Phillips
j.phillips@abdn.ac.uk
44-122-427-3174
Census of Marine Life
22-Feb-2006