Australian media reports have sensationalised sharks and shark encounter for over 150 years. These types of stories do little to inform the public of the truth about sharks and their behaviour or the risk of encountering shark. The sensationalised media stories often promoted fear within the general community but the ASAF wants to turn that fear into respect for these much maligned animals by making available factual information to educate people via the Taronga Conservatiion Society Australia web site and from published scientific papers.
Known Dangerous Sharks
There are over 510 species of shark worldwide and 182 of these sharks have been found in Australian waters (as of 2010), but only a handful are known to be dangerous to humans.
The types of sharks implicated in the majority of unprovoked attacks on humans in Australian waters include the White, Tiger and the Bull Shark all of which are capable of inflicting much more damage to humans than they do. The majority of people that are bitten are usually bitten once and released. This may indicate that the shark is not biting to procure food (as commonly thought) in the majority of cases but rather they may be investigating an interesting object or possibly mistaken a person for their normal prey and call off the attack when they realise that the taste from the explorative bite or possibly because the objects behaviour is different from their normal prey. Around 30 percent of all recorded attack cases do not result in an injury to the victim (eg bites to surfboards or the shark was pushed away before it can bite them, etc).
The following animals have been identified in fatal unprovoked shark attacks on humans in Australia:
· White Shark (Carcharodon carcharias)
· Tiger Shark (Galeocerdo cuvier)
· Bull Sharks (Carcharhinus leucas) - one of several Whaler Shark species that occur in Australia.
It must be remember that any large animal should be considered potentially dangerous to humans (on land or in the sea) and sharks 2 metres or larger should also be considered potentially dangerous.
Most shark encounters typically occur in nearshore waters where most people go. Swimmers encounter sharks inshore of a sandbar, between sandbars or near drop offs to deeper water. Surfers typically encounter sharks on the seaward side of the waves also near deeper water where larger free swimming sharks can approach without being observed. A vast majority of victims do not see the shark until it initiates the encounter.
There are several theories as to why sharks bite humans including hunger, inquisitiveness (i.e. testing an object with their mouth to see if it is edible), possibly mistaken identity or invasion of the shark's personal space by the human. Many years ago there was a 'rogue' shark theory where it was thought an injured shark unable to feed normally starts to hunt humans. However, there is no scientific evidence to support this theory. It is not know if there are common motivating factor involved in all shark encounters because each shark/human interaction is unique and behavioural and environmental circumstances are different in every case. The only consitent circumstance is that people and sharks are in the water at the same location at the same time when the encounter occurs.
Modern sharks have been on this earth for over 200 million years and humans for around 200 thousand years (the earliest human remains found to date are 200,000 years old. However, it is only in the last century that people have regularly entered the ocean on mass to swim. Sharks do not eat people regularly, nor are humans in the water for long enough to allow sharks to eat humans consistently to include them in their natural diet. In some cases sharks have consumed humans but this is a rare event. Records for Australia since 1791 indicate only 201 unprovoked fatalities occurred over that time (220 years) and only 42 cases were recorded where the body was not recovered and presumed eaten. There are also cases where sharks have removed a limb from avictim only to spit it out and swim away. If sharks did eat humans as part of their natural diet there would be tens of thousands of people attacked and eaten every year and this clearly does not occur. Humans can only be considered an accidental prey item.
Estimating the number of Sharks in Our Oceans.
Shark populations generally are considered to be in steep decline in Australia and around the world due to overfishing. Scientists consider that populations of large predatory fish including sharks have declined dramatically since the 1980s. One cause is the high price obtained for shark fins in Asia, where there is great status attached to eating shark fin soup. Australia along with many western countries have banned the shark fin trade and the selling of shark fins without an attached shark. Estimates vary from 26 to 78 million sharks killed per year for their fins. But some fisheries experts suggest that this figure could be over 100 million sharks killed due to the unregulated and illegal fishing activities around the world.
The simple answer is that there is still no well defined way of estimating the number of sharks in our oceans. In relation to the shark species known to bite humans there is no scientific evidence that indicates an increase in numbers for those species. It is also known that sharks generally do not have the capacity to increase in numbers quickly. The shark’s life history (long lived, slow growing, late age at maturity and give birth to only a few offspring) means that shark populations cannot increase rapidly and so sudden explosions in the population of sharks is not possible. Sharks have a low resilience to fishing pressure and their capacity for recruitment makes it extremely hard for sharks to recover from overfishing (targeted and unmanaged shark fisheries, finning, long line fishing, etc). This is evident with the protection of the harmless Grey Nurse Shark along the east coast of Australia which have not recovered to anywhere near natural population numbers in over 25 years.