Basics of Sharks
- Sharks have roamed our seas for more than 400 million years, which means they inhabited the earth for nearly 200 million years before dinosaurs.
- Sharks are fish with skeletons made of cartilage instead of bone, but sharks’ slow growth and late maturity mean they have more in common with sea turtles and marine mammals than bony fish such as flounder or tuna.
- Sharks are a remarkably diverse group of fish. They range from less than a metre to 20 metres in length; they are found in most coastal regions but also in the deep ocean and even in fresh water. Some sharks lay eggs, but most give birth to live young. Most are top predators while a few feed on plankton. Sharks in turn are preyed upon by other sharks and sometimes killer whales.
- The term ‘shark’ often refers not only to shark species but also to the closely related rays and skates, as well as the oft-overlooked chimaeras (rat, rabbit and elephant fish).Collectively these cartilaginous species are known as chondrichthyan fish (forming Class Chondrichthyes).
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Sea Shepherd
Sea Shepherd is best known for its frontline work protecting marine mammals but its broader mandate is to protect all ocean creatures. Styled on the more widely publicized organization Greenpeace, Sea Shepherd continued to grow teeth where Greenpeace lost them through inactivity. Sea Shepherd’s founder Captain Paul Watson has a reputation for pursuing illegal whalers and longliners, harassing seal cullers, organizing rallies, and generally irritating governments that would rather turn a blind eye, and infuriating fishing consortiums who would rather go about their illegal and often cruel practices unnoticed.
Sea Shepherd’s flag ship The Farley Mowat has harassed shark fishing boats in Costa Rican waters and sent sailors sprawling over their decks after being hit by The Marley Mowat’s water cannons.
Captain Watson also manages to fit a lecture circuit into his busy schedule, during which he educates anyone willing to listen on the plight of whales, dolphins, seals, and sharks.
Sea Shepherd’s second vessel is on permanent patrol in the Galapagos area where Park Rangers are virtually helpless against the Ecuadorian fishing boats that brazenly ignore the protection afforded to the park by its world heritage site status. Even with Sea Shepherd’s vigilant patrols the rangers are so out numbered that fishermen have an almost unimpeded run of the islands and the Galapagos Sharks that once schooled in vast numbers around Darwin Island have all but vanished.
This kind of hard line activism is not for everyone. The Sea Shepherd crew have been deported, locked up, threatened, and roughed up on many occasions. Violent confrontations at sea may not fit with your particular code of behavior or ethics but what makes you more uncomfortable: sponsoring Sea Shepherd’s activities that achieve direct results in the protection of endangered creatures, or lobbying deaf government officials while the wholesale slaughter of our oceans sharks and whales continues unchallenged?
If Sea Shepherd seems like a worthwhile organization with which to take a stand, you can help them in a variety of ways. Joining Sea Shepherd with a modest contribution, helps with the provisioning, fueling, and maintenance of their ships. As a member you may also have the chance to sign on as a volunteer for a tour of duty on one of their campaigns. On their website they list what skills they are looking for in new crew members but they also take unskilled deckhands that are willing to work hard.
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Scientists Trace Origin Of Shark’s Electric Sense
The dark markings indicate gene expression in the electrosensory organs in the head of an shark.
Gainsville, Florida (Feb 6 2006 18:53 EST) Sharks are known for their almost uncanny ability to detect electrical signals while hunting and navigating.
Now researchers have traced the origin of those electrosensory powers to the same type of embryonic cells that gives rise to many head and facial features in humans.
The discovery, reported by University of Florida scientists in the current edition of Evolution & Development, identifies neural crest cells, which are common in vertebrate development, as a source of sharks’ electrical ESP.
It also fortifies the idea that before our early ancestors emerged from the sea, they too had the ability to detect electric fields.
“Sharks have a network of electrosensory cells that allows them to hunt by detecting electrical signals generated by prey,” said Martin Cohn, a developmental biologist with the departments of zoology and anatomy and cell biology, and the UF Genetics Institute. “That doesn’t mean they can only detect electric fish. They can sense electricity generated by a muscle twitch, even if it’s the weak signal of a flounder buried under sand.”
Likewise, sharks are widely thought to use the Earth’s magnetic field for navigation, enabling them to swim in precise paths across large expanses of featureless ocean, Cohn said.
“If you think of this in the big picture of evolution of sensory systems, such as olfaction, hearing, vision and touch, this shows sharks took a pre-existing genetic program and used it to build yet another type of sensory system,” Cohn said.
UF and University of Louisiana researchers analyzed electroreceptor development in the embryos of the lesser spotted catshark, an animal that is largely motionless during the day and hunts at night, mainly in the seagrass beds of the eastern Atlantic Ocean.
Using molecular tests, scientists found two independent genetic markers of neural crest cells in the animal’s electricity-sensing organs. Analysis shows these cells migrate from the brain and travel into the developing shark’s head, creating the framework for the electrosensory system – a previously unknown function of a much-studied group of cells, according to Renata Freitas, a doctoral candidate in UF’s zoology department and first author of the paper.
The process mirrors the development of the lateral line that allows fish to mechanically sense their environment, and organs of the inner ear that enable people to keep their balance. But scientists suspect as human ancestors emerged from the sea, they discarded their lateral lines as well as their ability to sense electrical fields.
“Our fishy ancestors had the anatomy for it,” said James Albert, a former UF biologist who is now at the University of Louisiana. “You can imagine how valuable this system would be if you were aquatic, because water is so conductive. But it doesn’t work on land – air doesn’t conduct electricity as well. When it happens, it’s called a lightning bolt and you don’t need special receptors to sense it.”
All primitive animals with backbones could sense electricity, according to Michael Coates, an associate professor of organismal biology and anatomy at the University of Chicago. Mammals, reptiles and birds lost the sense over time, as did most fish alive today.
But in sharks and a few other species, such as sturgeons and lampreys, electrosensory capability endured.
“Most fish you see today have large eyes,” Coates said. “But sharks are predators that do not particularly rely on vision. If you see a hammerhead shark searching for flatfish, it moves its head back and forth, almost as if it were using a metal detector. Knowing that the electrosensory system may have developed with involvement of neural crest cells is valuable for people trying to reconstruct vertebrate evolution. It gives us further indication of how all of the various sensory systems come on line.”
But the idea that the neural crest truly is the source of the electrosensory system will raise eyebrows, scientists say.
“It’s a very interesting paper for two reasons,” said Glenn Northcutt, a distinguished professor of neuroscience at the University of California, San Diego, and a leading expert in vertebrate neurobiology. “For the first time, someone has shown which molecules may be responsible for guiding the development of the receptors of the lateral line system. I think this will hold true and is a very important finding. But I’m skeptical about the claim the neural crest gives rise to electroreceptors. It still requires a definitive experiment, where the developing neural crest cells are marked with dye, the embryo develops and the dye clearly shows up in the electroreceptors.”
Dye tests are a classical way of mapping cell movements during development, and have been used to explore the origins of limbs and brain cells. In the current research, scientists used genetic markers to trace neural crest cells.
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SHARKWATER FILM
The Canadian born photographer and filmmaker never held a video camera before he began the Sharkwater project — but that is not apparent when you see the film. On the contrary, the imagery is beautifully framed, inspiring, and stunningly breathtaking. The images that Stewart sets forth will awe you, and will capture your heart.
Stewart set out to create a film that would simply depict how beautiful sharks are in their natural habitat. The finished product, however, ended up evolving into so much more. Instead, we’re drawn into an amazing story of human drama, organized crime, corruption, and greed.
The film kicks off with clips from military training videos archived from the 1960s. As might be expected, they depict sharks as ruthless and bloodthirsty man-eaters. The clips belie the ignorance of their times with suggestions such as putting one’s face in the water and yelling to deter a marauding shark.
While it provides an almost humorous relief to the serious subject matter, it is important to realize that 40 years ago, these films were definitive and authoritative. Forty years ago, we held these precepts to be truth. We look back and laugh, because now we know better. …Or do we?
The chasm between reality and the popular beliefs sustained and fueled by exaggerated media is still enormous.
In reality, sharks do not eat people, and they are not mindless killers. As long as people view sharks as dangerous predators, they won’t care about saving them, and this is exactly what Rob Stewart hopes to change.
Early in the film, Stewart begins to debunk some of the mystery and fear around sharks as he holds and pets an eight foot long Caribbean reef shark as if it were a lapdog. From this point on, his understanding of sharks and his community with the underwater world is evident.
In an effort to capture even more compelling underwater footage of sharks, Stewart joins renowned conservationist Paul Watson and the controversial Sea Shepard team aboard the Ocean Warrior. The team is invited and implored by the President of Costa Rica to help patrol the waters surrounding Cocos Island, one of the places celebrated as a gathering area for sharks, and where illegal shark fishing often takes place.
Complete with colliding ships, gunboat chases, espionage, corrupt courts, and spurious charges of attempted murder, the adventure that ensues is nothing short of epic.
Organized crime and conspiracy surrounding the shark fin industry is deeply entrenched. With dried fins sometimes fetching in excess of $400USD per pound, it is a multi-billion dollar industry rife with greed and corruption.
But it is more than corrupt government officials, or the “shark-fin mafia” that threaten Stewart’s life. Shortly after the entire crew must hurriedly flee from Costa Rica, Stewart is diagnosed with necrotizing fasciitis, the “flesh-eating” disease. Rare but deadly, the disease threatens to claim Stewart’s leg, and possibly his life. Alone, with only hope by his side, Stewart remains bedridden in a Panamanian hospital for an agonizing week before doctors can make any prognosis.
Determined more than ever to make a difference, Stewart defies reason and returns to Costa Rica. Knowing he would be arrested on sight, he and his crew must sneak back into the country. Ironically, when they arrive in Puntarenas, they are able to blend in — Protesters line the streets, demonstrating against shark finning and illegal shark fisheries. “Costa Ricans were rallying for sharks. . . I realized our adventure had helped awaken a country”, remarks Stewart with renewed faith.
Over the next four years, Stewart shot more than 400 hours of footage in 15 different countries. In addition to interviews with shark and conservation experts like Erich Ritter, Patrick Moore, and Rex Weyler, Sharkwater includes commentary from average beachgoers, showing how desperately fear and hate of sharks are ingrained. As one Australian angrily believes, “they’re the scourge of the ocean, and everyone should go and catch one.”
Sharks have been an integral part of the oceanic ecosystem for 400 million years, but their populations have declined by more than 90% in the last 50 years alone. It is estimated that more than 100 million sharks are killed for their fins each year.
Shark finning is neither humane nor sustainable. Any shark is taken, regardless of size, age, or species. After its fins are cut off, the shark is thrown back into the water. Unable to swim, and bleeding to death, the shark suffers a slow and torturous death.
Much of the demand for the fins stems from shark fin soup, a traditional asian dish often served at weddings and special events. Once a rare delicacy consumed by Chinese aristocracy, the dish is viewed as a symbol of status and power, and is gaining in popularity as China continues to modernize and its 1.2 billion people become more affluent.
Indeed, there is an uphill battle to be fought, but there is hope.
The Sharkwater crew interviews one Chinese bride who, defying long tradition and facing cultural stigma, makes a statement by refusing to serve shark fin soup at her wedding banquet. We can only hope that this — what is now seen as a controversial decision — will eventually become the norm.
With its spellbinding cinematography and riveting story, Sharkwater has won awards at every film festival where it has appeared. Sharkwater will change the way people view sharks and the ocean. It will open their eyes. . . and, hopefully, their hearts. You can create pet chrome emblems with Shark image to create awareness too.
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