An international team of scientists says the absence of sharks from abyssal regions of the world's oceans may mean some species are in danger of extinction.
The findings mean the world's oceans are about 70 percent shark-free, researchers said.
The oceans' abyssal zone remains in perpetual darkness at depths below 6,560 feet, with immense pressures of nearly five tons per square inch at its deepest.
It had been hoped that, as man explored deeper into the abyss, new shark species would be discovered. Scientists do not know why sharks are absent from the deep, but suggest one possible reason might be a lack of food.
They warn their finding has environmental implications. Professor Monty Priede, director of Oceanlab at the University of Aberdeen in Scotland said: "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 findings are published in the Proceedings of The Royal Society, Biological Series.
Copyright 2006 by United Press International
Explore further: Awarded a Pell Grant? Better double-check