S.C.U.B.A. Diving

Marine scientists have discovered that the deepest oceans of the world would appear to be shark free.
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, distribution and diversity of life in the world's oceans. The team also used findings built up over the last two decades when the University of Aberdeen's Oceanlab started developing landers - remotely operated vehicles - which have been used in deep waters all over the world. Expeditions usinglanders visited the deepest abyssal plain on the planet - North of Hawaii; the South Atlantic off the Falkland Islands; the North West African slopes off Angola, the North East Atlantic Ocean, West of Ireland, and five research cruises in the North East Atlantic. The scientists say that the deepest confirmed report of a shark is at 3,700m. They believe it is very unlikely that major new populations will be discovered in abyssal regions. Professor Priede added: "As far as we can see there is no hidden reserve of sharks in the deep sea. All we see, is all there is, it's highly unlikely we are going to find anymore."

Source: http://www.ocean.com/resource.asp?resourceid=5188&catid=5&locationid=2

by Underwatertimes.com News Service

Mexico City, Mexico (Mar 2, 2006 19:26 EST) A Mexican marine biologist has discovered a new shark species in the murky depths of Mexico‘s Sea of Cortez, the first new shark find in the wildlife-rich inlet in 34 years.

Postgraduate student Juan Carlos Perez was on a fishing boat in early 2003 studying sharks from the Mustelus family netted at depths of 660 feet when he noticed some of them had darker skin and white markings.

The sharks, slender, dark gray-brown and around 5 feet (1.5 meters) long, turned out to be a new species that Perez and his team have named "Mustelus hacat," after the word for shark in a local Indian dialect.

"What I first noticed was their color. They are dark in color, like dark coffee, and have white markings on the tips and edges of their fins and tails which jump out at you because they are so dark," Perez told Reuters on Thursday.

"I got back from the boat and the first thing I said was that I thought I had a new species, but I wasn‘t sure until six months on when we did genetic tests," he said, audibly elated.

Worldwide, marine biologists tend to discover two or three new shark species in any given year.

But Perez‘s find -- bringing to five the types of Mustelus shark found in the eastern North Pacific -- is the first shark discovery in the Sea of Cortez since the tiny Mexican Horn Shark (Heterodontus mexicanus) was identified in 1972.

"I wasn‘t looking for something new, but it‘s very satisfying. I‘m very happy," said Perez, 31, who is based at the CICESE science and technology research center at the port of Ensenada in northwestern Baja California state.

His find was published in the U.S. journal Copeia in December.

"There must be more undiscovered species there but access is difficult. If we hadn‘t been on those boats I‘d never have seen them because that‘s the only place they are caught. And it‘s not a region that attracts scuba diving."

There are some 50 to 60 species of shark in the Sea of Cortez, a narrow body of water also known as the Gulf of California that separates Mexico‘s Baja California peninsula from the mainland and is famous for its rich and unique ecosystem.

The Mustelus hacat lives in the ocean‘s depths feeding on shellfish and shrimp," Perez said, adding: "They have very, very small teeth. They are really not aggressive or dangerous."

Source: http://www.underwatertimes.com/news.php?article_id=97101054832