Hammerhead Shark: From ThinkQuest:
The great hammerhead shark has a wide, thick head with the eyes at the margins. The head is indented at the center of the 'hammer,' which is almost rectangular in shape. This shark is gray-brown above with an off-white belly. The first dorsal fin (the large fin on the top of the shark that most people associate with sharks) is very large and pointed. The average great hammerhead shark is up to 11.5 feet (3.5 m) long. The largest reported was 20 feet (6 m) long. These large sharks average about over 500 pounds (230 kg) but can weigh as much as 1,000 pounds (450 kg).
An article in ScienceDaily reports that about 100 million sharkes die each year, a rate that makes it unsustainable to maintain shark populations; whether or not you like sharks, they play an important role in maintaining the ocean's ecosystem. The sharks' effects on the marine ecosystem are beginning to be better understood by scientists, and their decine is not promising news. The decline in shark populations is due to a number of factors, including producing few offspring, taking a long time to achieve maturity and being killed for food for their fins, e.g., shark fin soup common to Asian cultures.
Sharks have persisted for at least 400 million years and are one of the oldest vertebrate groups on the planet. However, these predators are experiencing population declines significant enough to cause global concern," explains lead author Boris Worm, professor of biology at Dalhousie. In the recently published paper, "Global Catches, Exploitation Rates and Rebuilding Options for Sharks," Worm and three other researchers from Dalhousie University teamed up with scientists from the University of Windsor in Canada, as well as Stony Brook University in New York, Florida International University (FIU) in Miami and the University of Miami, to calculate total shark mortality and outline possible solutions to protect the world's shark populations.
"This is a big concern because the loss of sharks can affect the wider ecosystem," said Mike Heithaus, executive director of FIU's School of Environment, Arts and Society and co-author of the paper. "In working with tiger sharks, we've seen that if we don't have enough of these predators around, it causes cascading changes in the ecosystem, that trickle all the way down to marine plants." Such changes can harm other species, and may negatively affect commercial fisheries, Heithaus explains.
Based on data collected for the latest study, shark deaths were estimated at 100 million in 2000 and 97 million in 2010. The total possible range of mortality is between 63 and 273 million annually.
The biggest culprit in the significant population decline is a combination of a global boom in shark fishing -- usually for their valuable fins -- and the relatively slow growth and reproductive rates of sharks. Because adequate data of shark catches is lacking for most of the world, the wide range of possible mortality is based on available data of shark deaths and calculated projections for unreported, discarded and illegal catches. But even with the uncertainty there is little question that sharks are being caught faster than they can reproduce.The best idea, of course, is to offer some level of protection to sharks, allowing them to reproduce at a sustainable rate that balances the needs of commercial fisheries and those of marine ecosystems. About 6 percent of sharks die each year due to fisheries, not an insignificant amount. Existing regulations exist in some cases, but unless these are enforced by governments, they will do little to stop the decline in shark populations. But there remains hope; this week an important international conference—Conference of the Parties to the Convention on International Trade in Endangered Species— is taking place in Bangkok:
The information from this report comes at a critical time, as 177 governments from around the world will attend the March 3-14 meeting of the Conference of the Parties to the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) in Bangkok. CITES is widely considered one of the best tools for protecting vulnerable species from extinction. Hammerheads, Oceanic whitetip, and porbeagle sharks are currently being considered for protection under CITES.