SCUBA Diving News

A new scientific study has concluded that sharks in the Mediterranean Sea have declined by more than 97 percent in abundance and “catch weight” over the last 200 years.

The findings of the study published in the journal Conservation Biology, suggest several Mediterranean shark species are at risk of extinction, especially if current levels of fishing pressure continue. Study lead author Francesco Ferretti and his colleagues are concerned that the declines in sharks may have implications for the broader Mediterranean marine ecosystem.

Ferretti said: “The loss of top predators such as sharks in other sectors of the Atlantic has resulted in changes to the ecosystem. These changes are unpredictable and poorly understood but given the decline in Mediterranean shark numbers, there is cause to be seriously concerned about the effects this could have.”

Forty-seven species of sharks live in the Mediterranean Sea, of which 20 are considered top predators.

The study authors only had enough information to assess the status of five of the twenty large predatory shark species in the Mediterranean. Of those analysed, almost all of the large sharks have decreased in abundance because of unintended capture in open ocean fisheries, targeted shark fishing, and human population pressure in coastal areas. Sharks are especially vulnerable to overfishing and slow to recover from depletion because they generally grow slowly, mature late and produce few young.

The mean size of sharks caught in the Mediterranean is among the lowest in the world. The study reveals that size and weight declines over time indicate that more young and immature sharks are being caught.

There are currently no catch limits for commercially-fished shark species in the
Mediterranean Sea. A comprehensive monitoring program for fisheries has been difficult to implement in the Mediterranean because of the artisanal (small and localized) nature of its fisheries and the large number of countries bordering the sea.

Only five species of sharks offered sufficient information for analysis, including the blue shark, one thresher shark species, two mackerel shark species and one hammerhead shark species. The blue, smooth hammerhead and thresher sharks were classified as “Vulnerable” according to the latest IUCN-World conservation Union Red List Criteria for extinction risk. Two mackerel sharks, porbeagle and shortfin mako, were classified as “critically endangered”. Many other large sharks are classified as “Data Deficient”.

To view a summary of the Conservation Biology paper, visit:
http://www.lenfestocean.org/publications/ferretti_med_sharks.html
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Labels: environment, Mediterranean, research, sharks

In a surprising move, the Mexican government has published sweeping new regulations and protections for sharks, including a shark finning ban, an extension of the moratorium on new commercial shark fishing permits, and extensive protections for great white sharks, whale sharks, basking sharks and manta rays.

"Mexico has taken a real leadership position here" says Patric Douglas CEO of Shark Diver (www.sharkdiver.com). "The rest of Latin America is watching what Mexico does with great interest now, this is good news indeed".

In the past few years Mexico has been recognized as one of the few places on the planet where large congregations of Great White sharks appear each year at Isla Guadalupe. Along with Whale shark aggregations in Holbox, destination tourism with these shark species and others is growing.

Captain Mike Lever owner of expedition dive vessel MV Nautilus Explorer was thrilled at the news "The people of Mexico afford us a great privilege in allowing us to dive with the white sharks at Guadalupe Island. The February 14th enactment of Mexican rules for responsible shark and ray fisheries is incredibly good news and really bodes well for the survival of these magnificent animals. Our hats are off to all of the scientists who helped make this happen".

The new rules and regulations came after 10 years of debate and the broad support of researchers, scientists, conservations groups, eco-tour operations and local citizens.


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Labels: environment, sealife, sharks

Three to four times as many sharks are killed for their fins as are reported in the official figures.

Researchers looked at trade in shark fins, and used genetic identification to estimate by species the number of globally traded shark fins.

The results are the first fishery-independent estimate of the scale of shark catches worldwide. If the estimates are correct for one of the most commonly traded species, the blue shark, then the nubers being caught are very close to the maximum sustainable levels.

Increasing awareness of the vulnerability of shark species to exploitation and a proliferation of finning (i.e. removal of fins and discarding of the carcass at sea) have contributed to growing concerns that the fin trade may be driving shark catches to unsustainable levels.

The research was led by Shelley Clarke of Imperial College London who has lived in Asia for over 12 years.

Hong Kong is world's largest shark fin market with at least half of the global trade.

Sources:
Ecology Letters, Volume 9, Number 10, October 2006, pp. 1115-1126(12)
Conservation Biology Volume 20, No. 1, 201–211


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Labels: sealife, sharks

When the genetic make-up of globally distributed marine species are studied, it is often found that there are significant differences between populations. The differences may be so great that what was thought to be one species is actually two.

A recent study into scalloped hammerhead sharks, Sphyrna lewini, shows that although the fish in the Atlantic and Indo-Pacific populations appear identical, genetically they are different. The scalloped hammerhead in the western north Atlantic is actually a new, cryptic, species.

The study concludes that effective management of large coastal shark species should incorporate this discovery. It indicates that the cryptic scalloped hammerhead is less abundant than S. lewini, making it potentially more susceptible to fishery pressure.

Journal Reference: Marine Biology, Volume 148, Issue 5, Mar 2006


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Labels: sharks

Shark attacks dropped in 2005 because people are fighting back when attacked and shark populations are decreasing, according to a University of Florida report.

Worldwide there were 58 shark attacks in 2005, of which only 4 were upon divers. This is down from 78 attacks in 2000.

Part of the reason for the trend is that there are fewer sharks, a result of a decline caused by overfishing of this slow-to-reproduce animal. The other factor is that people are defending themselves more aggressively.

What should you do as a diver if you see a shark? George H. Burgess of the International Shark Attack File advises you to
"Stay calm and maintain your position in as quiet a manner as possible. Most sharks merely are curious and will leave on their own accord. Enjoy your opportunity to see one of nature's most magnificent predators.

If a shark begins to get too interested, the best strategy is to leave the water watching the shark all the time, with your dive partner close at hand. Sharks are less likely to attack a 'school' of divers than a solitary individual."

He goes on to say that if the shark is acting overtly aggressive then back up against whatever structure (reef, rock outcropping, piling) is available. If you are in open water, orient back-to-back with your dive partner and gradually rise to the surface and the safety of your boat.

If a shark attacks, the best strategy is to hit it on the tip of its nose. If it bites then be as agressive as possible and claw at the eyes and gill openings.

Further Reading: International Shark Attack File

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Labels: sharks

A great white shark, nicknamed Nicole, has made the journey between South Africa and Australia and back in under nine months. The new research published in Science is the first proof of links between populations of different continents.

"This is one of the most significant discoveries about white shark ecology and suggests we might have to rewrite the life history of this powerful fish," said researcher Dr. Ramon Bonfil, shark expert and lead author of the study. "More importantly, Nicole has shown us that separate populations of great white sharks may be more directly connected than previously thought, and that wide-ranging white sharks that are nationally protected in places such as South Africa and Australia are much more vulnerable to human fishing in the open oceans than we previously thought."

The story of Nicole began on November 7, 2003, when Bonfil and his colleagues from the Marine and Coastal Management Department of South Africa and the White Shark Trust attached a satellite tag to Nicole’s dorsal fin as part of a large study on white shark migrations. The tags—specifically known as pop-up archival tags—record data on time, temperature, water depth, and light levels as the shark moves through its habitat. On a pre-recorded date, the tag detaches from the shark and floats to the surface, where it transmits its data sets to a researcher’s computer via satellite.

An additional 24 white sharks were tagged with similar tags and seven more with real-time satellite tags during this study, with Bonfil and his team often having to wrestle the dangerous sharks while on a cradle in order to fix the satellite transmitters to their dorsal fins. While most of the tagged white sharks revealed at least three different movement patterns, including wide-ranging coastal migrations up and down the eastern side of South Africa, Nicole headed out into the vast and deep basin of the Indian Ocean. The track estimated from the data transmitted by the tag revealed that Nicole followed a strikingly direct route towards Australia, on a path void of oceanic islands. Although Nicole took frequent plunges to depths as great as 3,215 feet (980 meters—a record for white sharks) while crossing the Indian Ocean, she spent most of her time (61 percent) swimming along the surface, leading researchers to suspect that perhaps great white sharks use celestial cues for transoceanic navigation.

Ninety-nine days later, Nicole was swimming about a mile from shore just south of the Exmouth Gulf in western Australia, where her tag detached and floated to the surface with all of her secrets.

This leg of the journey alone—some 6,897 miles (11,100 kilometers)—was one for the record books. However, Nicole would resurface again on August 20, 2004, not in Australian waters, but back in Gansbaai, South Africa, where she was tagged just under nine months before. Her distinctively notched dorsal fin was photographed by Michael Scholl, one of Bonfil’s team researchers and compared to previous photographs he had taken over a period of six years. After a detailed comparison of images of dorsal fin notches and markings, there was no longer any doubt: Nicole had returned to her home waters.


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Labels: sealife, sharks

A recently issued Eyptian decree will finally ban shark fishing in the Red Sea. This gives the conservation association HEPCA the legislative means to put a stop to the dozens of shark massacres that are reported daily throughout Egypt's Red Sea coastline from Hurghada to Marsa Alam

Shark fishing has, theoretically, been illegal since 1973, when Egypt became one of 100 countries to sign the CITES (Convention of International Trading of Endangered Species) Treaty. Sharks in the Red Sea were on CITES' list of endangered species, but the Egyptian law that regulates fishing made no mention of sharks.

"Sharks are a valuable source of revenue for the country. Many people don’t realize that tourists spend millions of dollars in the Red Sea because of the sharks. For example, a dive destination like the Brother Islands (off the coast of Marsa Alam) is sold primarily because of its abundant shark population. It has been estimated that each shark in the Red Sea generates approximately 10,000 pounds sterling in income to the country," said HEPCA's Director.

The problem began to reach alarming levels in 2000, when divers and conservationists started noticing a marked decrease in shark populations. The decline in numbers was mainly attributed to an increase in the number of fishing boats in the Red Sea.

This new wave of commercial fishing, coupled with the rise of a handful of trading companies that were being established solely for the purpose of exporting in-demand seafood delicacies (including sea cucumbers and shark fins) to the Chinese market, were an environmental catastrophe in the making.

It is difficult to quantify Egypt’s current shark population and how much it has suffered over the years, but divers claim that sites near Sharm El-Sheikh and Hurghada that have always been known as prime shark viewing destinations are becoming less and less inhabited with by sharks.

More info: http://www.egypttoday.com/article.aspx?ArticleID=5918

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Labels: sealife, sharks