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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The Shark Safe Network
The Shark Safe Network provides a framework to combine and focus the efforts of committed individuals and shark conservation groups towards specific shark conservation campaigns. If you have a passion to protect sharks, Shark Safe Network helps you to get involved and make a difference – by participating in a current campaign or by launching your own campaign in your community.
Shark Safe Network provides the information, tools, raw materials and support. You provide the passion!!
The goal of every Shark Safe Network campaign is to reduce and ultimately eliminate wasteful and unsustainable activities and products that threaten sharks’ survival. Shark Safe Network invites and welcomes participation from any and all organizations and individuals, provided that all campaigns are conducted according the Shark Safe Network campaign principles.
And we always keep in mind that helping sharks = helping people. When you consider any of the issues that threaten sharks today, there is also a corresponding negative impact on humans and the planet.
Shark Safe Network is all about getting involved and doing something that counts. Join the Shark Safe Network and you will make a difference!
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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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SOS attend international conference in Brussels
Following its acceptance of membership to the recently formed Shark Alliance, Save Our Sharks (SOS) attended the first anniversary and inaugural meeting of the Shark Alliance member groups in Brussels.
Around 35 delegates from 6 countries, U.K, France, Italy, Germany, Switzerland and Holland attended plus the directors and staff from the Pew Charitable Trusts, who financed the meeting.
Save Our Sharks were represented by Nigel Proctor (on behalf of the SOS committee) who met up at Brussels airport with the Sea Anglers Conservation Network (Scotland) representative, and SOS liaison officer Denis Kelly.
“Fins On”
One of the principal proposals that came out the conference is to be headed “Fins On” where the aim is to have sharks landed whole. There will be a drive to raise public awareness of the issue, and we will try to capitalise on the IUCN red listing, and create further publicity.
“Shark Week”
Another proposal is to hold a “Shark Week” in each member country, where each country’s members create a project to involve the community, schools, museums, aquariums and the like to raise awareness of shark issues.
There will be more to follow on the above shortly
There were many other issues and points made, however, these are the principal ones
• Strive to raise public awareness of shark related issues,
• Create adequate publicity and maintain the pressure,
• Educate journalists away from ‘sensationalism’ without portraying sharks as an animal they clearly are not, they are apex predators, not cuddly, loveable ‘toys’,
• Pre-influence the journalist way of thinking prior to ‘shark week’ and Ocean Day,
• Feed the media with facts and data to ‘force’ the attention on sharks prior to EU discussions on shark management,
• Similarly with CITES,
• Important to maintain ‘shark friendly’ states and get them to lobby less friendly countries,
• Lobby the UK to dispense with its ‘special permits’,
• Ensure that the Shark Alliance has a high profile at the release and showing of the new shark film,
• Don’t alienate the fishing industry,
• Work with fishermen, more is likely to be achieved at a faster rate,
Denis and Nigel were made extremely welcome and clearly treated as being amongst equals, if but a little less experienced in the ways of policy and lobbying. Nigel stated after the meeting that, “We have made significant moves along the pathway of shark conservation and have little to fear in the future, in terms of acceptability, we have a lot to offer and should not be afraid to push forward with our objectives, we can gain a great deal from liaison with the other member groups of the Shark Alliance, however, we also have a great deal to offer as well”.
At the conference Nigel reiterated the high level of importance UK anglers attached to sharks, skates and rays, making the point that the bad old days of trophy fish were long gone. He finished off by indicating our commitment and referencing the prohibition on the landing of tope along the English east coast (c 200 miles of coastline) which to the best of our knowledge is the first full protection, and or prohibition on the landing of any shark species in European waters. This brought about a warm and consensual round of applause, which probably indicates that we are not outcasts any more, but highly regarded and welcome members of an important Shark Alliance.
Well done to Nigel and Denis for helping to put recreational shark fishing on the front-line of European shark conservation
The next few months
We are in for a quiet time in Scotland until after the elections but there is much to do, in England and Europe. We will be writing to our members shortly with more details, please get involved.
• Liaise with the Shark Trust to organise a “Shark Week” to raise public awareness with the overall goal of banning the removing of fins at sea.
• Lobby Defra to stop handing out special permits which allows finning on Porbeagles. Both of the above are part of the “Fins On” campaign.
• Keep pressure on Defra to announce the results of the tope consultation.
• Build up a case to take to the EU to implement tope management across Europe.
• Remind Defra of their intention to implement a maximum landing size on rays, skate and spurdog.
• Keep pressure on the Scottish Exec. to have the Firth of Lorne, Sound of Mull and surrounding lochs and waters designated as a Spurdog nursery area.
• Lobby the EU to have the 25 per cent by catch on rays implemented in all UK waters.
• Continue with the red tape to get SOS listed for charitable status. Once achieved we can apply for grants to help with the campaigning and administrative costs.
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A STING IN THE TALE FOR SHARKS AND RAYS
Expert findings show sharks and rays are now amongst Europe’s most threatened animals as more are added to the IUCN Red List of Threatened Species
Gland, Switzerland, 20 February 2006 (IUCN) The number of species of sharks and rays on the IUCN Red List of Threatened Species will increase based on the findings of a three-day expert workshop, hosted by the Joint Nature Conservation Committee (JNCC), that examined the conservation status of the species in the Northeast Atlantic and Mediterranean waters.
The workshop confirms the widely-accepted notion that slow-growing sharks and rays are exceptionally vulnerable to over-fishing, and that deep-water species are being depleted at an alarming rate. Some formerly important commercial species are now so rare that they are no longer being sought by fishermen, but their risk of extinction is still rising because of continued incidental capture in fisheries for more abundant species. This situation is exacerbated by the lack of shark fisheries management in European waters.
“Sharks and rays are amongst the most threatened animal groups in the UK today. I welcome the development of a Red List baseline, against which to monitor the hoped-for changes in their status that should arise from increased awareness of their plight,” said Dr Malcolm Vincent, JNCC’s Director of Science.
Nearly 100 species of sharks and rays were evaluated against the IUCN Red List Categories and Criteria. Categories range from Extinct to Least Concern and Data Deficient. Species deemed Vulnerable, Endangered or Critically Endangered are considered threatened with extinction and are added to the global IUCN Red List of Threatened Species. The IUCN Shark Specialist Group, which convened the meeting, will compile these assessments for a regional report that will include recommendations for conservation action.
Proposed additions to the Red List include three species of angel sharks, two species of skates, and several species of deep-water sharks, all of which are considered Critically Endangered in the region, as well as two species of coastal ray, now considered Endangered. The species found to be at lowest risk were generally small and fast-growing coastal species, like cuckoo ray and lesser-spotted catshark, and very deep ocean species that are still beyond the reach of today’s fishing fleets.
Angel sharks, formerly abundant large coastal sharks, were once a common sight in fish markets, but have largely vanished, almost unnoticed, from the European seas that are their world stronghold.
Now officially declared extinct in the North Sea by the International Council for the Exploration of the Sea (fisheries advisers to European countries), the angel shark was nominated in 2001 for strict legal protection in British waters, but we are still waiting for government action on this proposal, said Sarah Fowler, Co-Chair of the Shark Specialist Group. Workshop participants emphasised the urgency of protecting this, and many other imperilled species.
Three species of deep-water sharks, taken as incidental catch in fisheries and increasingly targeted for their meat and rich liver oil, were assessed as threatened. A population decline of 80-95% prompted a Critically Endangered classification for the region’s deep-water gulper shark.
These exceptionally slow-growing sharks are simply not biologically equipped to withstand such intense fishing pressure, said Tom Blasdale, Marine Species Adviser at the JNCC. We welcome recent European Union action to manage deep-water gillnet fisheries, but similar measures are still urgently needed to protect deep-water sharks taken by trawls and longlines.
The shortfin mako shark, a favourite target of commercial and recreational fishermen around the world, was proposed as Vulnerable in the Northeast Atlantic and Critically Endangered in the Mediterranean Sea.
This wide-ranging species is increasingly the target of fisheries and yet lacks any type of protective measures in this region, warned Alen Soldo of the Institute of Oceanography and Fisheries in Croatia. Of particular concern are mako sharks in the Mediterranean, where our findings revealed ongoing fishing pressure well beyond the reproductive capacity of the species.
In contrast to similar workshops held in North America, South Africa, and Australia, the workshop yielded little if any good news, due largely to the lack of shark and ray conservation measures in this region. Protection is granted by just a handful of European countries for the three largest species (basking shark, devil ray, and great white shark). The few European shark and ray quotas in place are routinely set far in excess of actual catches and therefore do not limit fishing pressure. They also cover only part of these stocks. Scientists advice for zero catch of many depleted shark and ray species has been ignored. There are no international limits on shark catch, even as fisheries for wide-ranging shark species (such as mako and blue sharks) expand and evidence of their declines mounts.
Scientists from government agencies, universities, and private institutions participated in the workshop including authors of published papers on shark and skate population status and experts who develop advice on shark quotas for European and international fisheries of the Northeast Atlantic. Experts from England, Scotland, Ireland, Italy, Spain, Portugal, Croatia, Russia, Sweden, Canada, and the USA took part.
The IUCN Red List of Threatened Species is the world’s most authoritative guide to the status of biological diversity. The workshop was the eighth in a global series to assess all of the world’s shark and ray species and develop regional conservation priorities. Resulting Red List proposals are preliminary until accepted by the global Shark Specialist Group network.
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