Why are sharks important to ocean ecosystems?

Sharks play a vital role in the oceans in a way that the average fish does not. Most sharks serve as top predators at the pinnacle of the marine food pyramid, and so play a critical role in ocean ecosystems. Directly or indirectly they regulate the natural balance of these ecosystems, at all levels, and so are an integral part of them. As they usually hunt old, weak or sick prey, they help to keep the prey population in good condition, healthy and strong, enabling these more naturally fit animals to reproduce and pass on their genes.  The effects of removing sharks from ocean ecosystems, although complex and rather unpredictable, are very likely to be ecologically and economically damaging.  For more information see:

http://www.supportoursharks.com/en/Conservation/default.htm

 

What dangers/threats do sharks face?

Sharks face a number of threats due to the high value of their fins, and demand for their meat and related products globally. The most accurate assessment to date of the impact of fishing on sharks suggests that between 63 and 273 million are being killed each year, with an average of approximately 100 million. For more information see:

http://www.supportoursharks.com/en/Conservation/default.htm

 

Does shark culling reduce the risk of attack?

Lethal shark control programs are designed to reduce the incidence of negative human/shark interactions. They do not, however, offer complete protection but instead work on the principle of "fewer sharks, fewer attacks". In New South Wales, Australia, between 1937 and 2008, 17% of shark bites occurred at beaches with shark nets installed, clearly indicating the ineffectiveness of shark nets to reduce bites to humans. Also, in Hawaii, between 1959 and 1976, a cull of 4,668 sharks including 554 tiger sharks, was carried out to reduce the number of shark bite incidents, yet there was no significant decrease in the rate of shark bites after the cull.

 

Can sharks be fished sustainably?

SOS does not support the fishing of sharks (commercially or recreationally/for sport or consumption), due to the stress inflicted during capture [1][2][3][4] and the unprecedented decline of most commercially targeted shark species. However, we recognise that some species of sharks may be more resilient to fishing pressure than others and so decisions regarding the appropriateness of such activities need to be continually reviewed at a species-specific level. Sharks reproduce very slowly, so even modest amounts of fishing can negatively impact local populations. On average, current known shark exploitation rates range between 6.4% and 7.9% of sharks killed per year. This exceeds the average sustainable exploitation rate for many shark populations, estimated from life history information to be approximately 4.9% per year, and explains the ongoing decline of most populations for which data exist. The consequences of these unsustainable catch and mortality rates for marine ecosystems could be substantial. Global total shark mortality, therefore, needs to be reduced drastically or stopped all together in order to rebuild depleted populations and restore functional apex predators to marine ecosystems.

 

How does the portrayal of sharks in the media affect their conservation?

In a 2012 study of 300 shark-related articles published in 20 major Australian and U.S. newspapers from 2000 to 2010, shark attacks were the emphasis of over half the articles analyzed, and shark conservation was the primary topic of just 11% of articles. Despite evidence that many shark species are at risk of extinction, the study found that most media coverage emphasized the risks sharks pose to people. To the extent that media reflects social opinion, these results highlight problems for shark conservation. The authors suggested that conservation professionals purposefully and frequently engage with the media to highlight the rarity of shark attacks, discuss preventative measures water users can take to reduce their vulnerability to shark encounters, and discuss conservation issues related to local and threatened species of sharks. When integrated with biological and ecological data, social-science data may help generate a more comprehensive perspective and inform conservation practice.

 

Do you think the public’s perception of sharks has changed in recent years?

A shift in public perception, from sharks being a danger to humans to humans being a danger to sharks, has captivated the attention of a new generation of ocean conservationists seeking to abolish the wasteful practice of shark finning.  Where international agencies have failed to protect sharks in the past, conservationists are now picking up the baton to take on the challenge, and their voice is growing ever louder as the public begin to realise the true value of sharks in our oceans.

 

What actions are currently being taken internationally to protect sharks?

Internationally, inclusion of species in the Convention on Migratory Species (CMS) and the Convention on International Trade in Endangered Species (CITES) is the goal for most groups working for the conservation of shark species, but strong opposition, typically from Japan and China, has previously hampered most efforts for their inclusion. CITES acts to restrict international trade in a listed species, whereas CMS aims to prohibit the taking of listed migratory species.

 

How can the public get involved in shark conservation?

I firmly believe that giving people the opportunity to participate in shark research is a great way of developing their understanding of the importance of sharks.  This is why I have developed SharkBase (www.shark-base.org). SharkBase is a global shark encounter database helping to map the distribution and structure of shark populations worldwide by encouraging the public to get involved and become a Citizen Shark Scientist by submitting past, present, and future shark encounters.

 

What is a shark and how are they different from rays?

Sharks and rays are fish with backbones (Vertebrates) that live in water, and breathes through gills.  A shark’s gills are found on the lateral side of the head whereas the gills of rays are found on the ventral side of the head.  Sharks and rays come under the subclass elasmobranchii, which basically means plate (elasmo) gills (branchii).  The skeleton of sharks and rays is made up of cartilage instead of bone like most other fish.  This allows elasmobranchs the flexibility in the water to swim fast and squeeze in and out of tight spaces.     

 

How many species of sharks and rays are there?

Worldwide, there are over 500 species of sharks and 700 species of rays, but these numbers are constantly being updated as we discover new species. 

 

Are sharks warm or cold blooded?

Most sharks are ectothermic (cold-blooded). Their inner body temperature matches the temperature of the water. However, some sharks, like the great white, can elevate their body temperature above that of their surroundings.

 

Do sharks blink?

Sharks don't blink. They have upper and lower eyelids, but these lids don't move and don't close over the eye. When biting prey, some sharks protect their eyes with a third eyelid called the nictitating membrane (A thin, tough membrane, or inner eyelid present in the eyes of many sharks. It can be drawn across the eye to protect if it from damage).

 

What is the largest shark?

The largest shark is the Whale Shark (Rhincodon typus). At over 14m, it's also the world's largest fish. The Whale Shark strains out tiny animals that drift in the sea, such as zooplankton and shrimp.

 

What is the smallest shark?

The smallest shark is the Dwarf Lantern Shark (Etmopterus perryi). It's less than 10 inches long and can be found in the cold, deep oceans. 

 

What is the fastest shark?

Most sharks are efficient swimmers. The highly streamlined Mako Shark has been clocked at speeds up to 22 mph.

 

Are sharks vicious man-hunters?

Sharks are highly-specialized predators, with sharp teeth, strong jaws, streamlined bodies, and powerful senses. However, sharks don't hunt humans; their feeding strategies evolved well before humans entered the water. Even today, of the 500 different shark species, fewer than ten are considered dangerous to humans. There are more than 7 billion people on our planet, and less than ten people are killed by sharks each year.  

 

How many rows of teeth do sharks have?

Most sharks have 5 to 15 rows of teeth in each jaw. Unlike human teeth, shark teeth don't have roots to hold them in place, so their teeth are easily broken off. A tooth usually lasts about a week before it falls out. When this happens, the tooth behind it moves up to replace it. A new tooth can be replaced in as little as 24 hours. Sharks keep replacing their teeth all their lives. As the shark grows, its new teeth keep pace and grow larger than the ones that are replaced.  Some species of shark have been known to have up to 20,000 teeth in one life time.

 

How long have there been sharks on the planet?

Sharks are some of the oldest and most successful vertebrates on the earth. The first sharks appeared in ancient oceans over 400 million years ago. For more information see:

http://www.supportoursharks.com/en/Education/Videos/How_Long_Have_Sharks_Existed.htm

 

Why don't we find more shark fossils?

Shark skeletons rarely fossilize. They are made of cartilage which decomposes so fast the tissue is not replaced by minerals. However, shark teeth are made of dentine and enamel and fossilize readily. A single shark may lose thousands of teeth in its lifetime. New sharp teeth replace old worn teeth which fall out and, sometimes, become fossils. Fossil teeth are often the only evidence of ancient sharks.