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What are the actual odds you’ll be attacked by a shark?

You’ve probably heard the news about two shark attacks happening in one day in the South West of WA, right in the middle of the Margaret River Pro, one of the biggest touring surf comps in Australia. As a result, the competition was cancelled due to concerns over the safety of competitors.

Punters showed mixed feelings about the cancellation, with many telling surfers to ‘toughen up’. Given the presence of whale carcasses in the region, as well as the close calls (thankfully no one was killed), we think the decision was the right one.

We also commend the competitors for being vocal about their fears, and showing other young people that admitting vulnerability is a positive and healthy thing.

However, if you’re a keen sailor, chances are you also enjoy time in the water too. Whether it’s diving, swimming, surfing or SUPIng, you’re taking a risk and entering the environment of a finely tuned ocean predator.

There has been a lot of press relating to increases in shark attacks in Australia, so we decided to examine real data on population increases and attacks, to see if there is merit to these reports.

Real Data on shark attacks in Australia

You’ve probably heard that shark attacks are on the rise in Australia, but is this statement actually true?

We took a look at one of the most trusted sources of shark attack stats in Australia, the Australian Shark Attack file (put together by the Taronga Zoo in Sydney).

The data breaks incidents into unprovoked and provoked attacks. According to the website:

  • Unprovoked – when a shark in its natural habitat tries to bite a human without any provocation by the human.
  • Provoked – when a human initiates or attracts physical contact with the shark – either on purpose or accidentally. This includes fishing and commercial diving activities.

But what about the data?

  • Recorded incidents between humans and sharks in Australia rose significantly from 1997 to 2017, for reasons that remain unclear.
  • During this time, the population in Australia rose by 33%. However, this doesn’t necessarily explain the rise in incidents.
  • If we correct for population growth in Australia, we can see that the percentage of recorded encounters are relatively small.

Percentage of shark encounters, adjusted for population growth in Australia (1997 to 2017)

  • Encounters, which resulted in injury rose by 1.59%
  • Encounters, which did not result in injury rose by 0.36%
  • Fatal encounters rose by 0.07%
  • Head here for the source on these figures.

Are more sharks in Australian waters?

Estimating the number of sharks in Australian waters is a difficult task. When experts talk about shark populations, they tend to refer to ‘Great White Sharks’ (now known as White Sharks).

White Sharks reach maturity at approximately 15 years (a relatively long time) and are migratory, which makes it even harder to estimate populations.

They became protected in the late nineties, so variations in population would only be noticed now(ish).

The CSIRO (via the National Environmental Science Program’s Marine Biodiversity Hub) use DNA analysis to determine reliable and detailed approximations of White Shark populations.

Their data shows that White Shark populations have experienced a slight decline since 2000, although this data pertains to adult White Sharks only.

Thanks to the time it takes for a White Shark to reach maturity, there is some uncertainty around juvenile populations. But, numbers for adults in East Australia are estimated at around 750 (an uncertainty range of 470 to 1,030 exists).

The southern-western adult White Shark population is approximately double in size, with around 1,460 in the region (and an uncertainty range between 760 and 2,250).

For more detailed information on how shark populations are measured, please head here.

What is the risk of a shark attack?

The Taronga Zoo researchers highlight the propensity for people to compare shark attack figures to car accidents, lightning strikes and other land-based events.

Although the risk of a shark attack is significantly less than these examples, they write that it’s not useful to compare terrestrial deaths with marine injury or death data.

The researchers prefer to compare shark attacks with other marine incidents, such as drowning while swimming at the beach, or other activities conducted in or around water.

They go on to say that shark attacks are a random event, which occasionally happen around Australia’s coast. Also, the greater the number of people in the water, the greater the risk of a shark encounter occurring.

This statement has been taken directly from Taronga Zoo’s FAQ page:

Conservatively, if 100,000 people went into the water at a beach, harbour or river just once per week around Australia’s 35,000+ km of coast over 52 weeks and there is one fatality per year then the risk of shark attack would be 5.2 million to 1. In reality there are many more people that go into the water each year (Surf Life saving [sic] Australia estimated 100 million beach visits in 2010) and the risk of dying from a shark attack is more likely rated at 50-60 million to one.

So, according to the data, the likelihood of being attacked by a shark and dying is 50 to 60 million to one. Of course, we’re not telling you to jump in the ocean with wild abandon.

Always listen to the advice of your Coast Guard and do not swim if there has been a shark warning in the area.

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