A new dataset on shark incidents in Australia stretching back to 1791 has found an increase in reported attacks, especially in recent decades, but researchers caution changes in the frequency and manner of reports need to be considered when examining the data.
The aim of the study, released by researchers at Taronga Zoo and Flinders University, is to better understand the factors that go into shark attacks to help authorities and experts mitigate and respond to incidents.
The researchers note that reported shark incidents have been increasing, however, little is known about why. And some of the variation might be an artefact of how the data was collected – not all shark attacks are reported and not all reports would have been found.
The data could also be affected by increasing populations or changing social norms around things like swimming.
“Reporting over time has changed” says Dr Phoebe Meagher from Taronga Zoo.
“In the last 10 years or so we’ve had social media and people are maybe more likely to report incidents than 50 or 100 years ago.
“So this database, like all historic, long running databases, has limitations for sure. But it is the longest running. It is the most comprehensive that we have. And having all that data, hundreds and hundreds of pieces of data that has been collected over 50 years, is an amazing resource.
“People have to be aware of those limitations, but they can also get good information from the database and hopefully be able to understand [things like] long term climatic patterns and how they might impact sharks.”
The dataset began as a passion project in the 1980s, with researchers in libraries looking up old newspaper articles and books.
The current database also includes data from government departments, questionnaires and forensic reports, and has more than 40 variables. These cover factors like shark species, environmental conditions and even what the victims were wearing or doing.
“So usually we have multiple ways that we try and validate the cases,” Dr Meagher said.
“We might get it initially through the media or through [a government department], and then we will look through forensic reports to confirm shark species and sometimes we will even speak to police and first responders.
“So we do try and draw on as much information from as many experts as we can to validate that data.”
The length of the dataset and the number of variables will allow researchers to examine many different factors. Which is important as scientists don’t know why shark bites are increasing.
“Globally and in Australia, shark bites on humans have increased steadily over the past few decades,” says Prof Charlie Huveneers from Flinders University.
“However, this increase isn’t happening everywhere, with shark bites decreasing in some regions and remaining stable in others. This reflects the high variability of the risk of being bitten by a shark.
“It is unlikely to be linked to only one factor and a combination of reasons likely contributes to the increased number of shark bites, including a growing human population spending more time doing water-based activities and recovering shark populations, or changes in shark occurrences along the coast.”
Guardian Australia adjusted the data for Australia’s growing population for the following chart:
“Sharks are getting a really bad reputation based on a couple of species. But sharks are really important for the environment and there are hundreds of species out there and a lot of them are in trouble,” says Dr Meagher.
“A whole bunch of things may increase the chance of having a shark in that area. But what actually increases the chance of being bitten? Who knows.”
“Getting this information out there is part of this growing trend to get data out of the dusty shelves of academics and into the public. Data science is the new way forward and let’s try and use this data for good.”
