The media appears to be reporting more and more shark encounters across Australia each year. But are shark bites increasing? Are there more sharks in our waters than ever before? Shark researcher and UQ graduate Dr Blake Chapman dives in to explain what’s happening beneath the ocean’s surface.

Sharks remain a hugely polarising and highly debated topic. The efforts we take (or don’t take) to mitigate the risk of shark bites continue to be argued among the public, policymakers, conservation groups, recreational water users, and even the scientific community. 

Shark bite incidence is undeniably increasing. However, there was a highly noticeable dip in statistics in 2018, with just 66 confirmed unprovoked bites across the globe.

When analysing and assessing shark bite statistics, we generally don’t pay attention to annual fluctuations, instead looking more at decadal averages. However, the drop last year was so significant that it was more representative of average statistics from the early 2000s. Although, even this comparison is complicated by the continual growth in communication efforts, human recreational water use, technological advances and the documentation of bites. 

There are a number of theories proposed for the drop in 2018, including reduced shark numbers and humans being more proactive in mitigating the risk. 

But, as with all things related to shark bites, there are no definitive answers. 

Despite the drop in global bite incidence in 2018, the total of 20 bites (including one fatality) that occurred in Australia last year was close to the country’s record of 22 bites in one year (which occurred in 2015).

In conjunction with the higher than average number of bites in Australia last year, we also saw some unusual bite patterns, such as the two bites at Cid Harbour in the Whitsundays within 24 hours, and then a third, fatal bite seven weeks later. 

Shark bites are random events, and unfortunately not often explainable. However, by retrospectively studying bite patterns from around the world over the past few decades, we have been able to identify some factors that may lead to a greater likelihood of human-shark interaction. 

These factors include anomalous climatic events (such as El Niño weather patterns), habitat modification or destruction and, of course, changes to the way humans utilise environments that overlap with sharks.

In conjunction with the steady, if not increasing, bite incidence in Australia, the media continues to fuel the fire around shark bites. 

Anything to do with human-shark interaction is major news. This includes actual bites, sightings (which are still often described with intent-laden terms, suggesting it was lucky that something traumatic did not occur) and governmental shark bite mitigation measures. 

Less prevalent are the stories that relate to the ‘positives’ of sharks, although, happily, interest in these stories is starting to increase. The media regularly reports anecdotal claims of ‘bigger and fatter’ sharks and shark populations that are ‘out of control’ or ‘in plague proportion’. 

Comments on localised sighting increases often come from long-term water users who spend large amounts of time in, on or around the water. Although not validated through any formal processes, these comments (minus any sensationalism and emotion) should not be quickly dismissed. This sort of information is not only important for devising and communicating warnings around present potential risk, but it may also be relevant to better understanding current and evolving shark movement patterns. Knowledge on movement patterns is so important and can greatly assist with developing, directing and optimising mitigation efforts. 

Although we are seeing more bites and talking about sharks more, we still don’t really know how healthy many of our shark populations are. 

If we listen to the media, sharks are everywhere! But we are also now looking for sharks and talking about shark sightings like never before. So, really, it is not surprising that we are seeing, but mostly talking about, sharks more often. This creates a perception that shark populations are increasing.

Australia is home to about 180 of the approximate 530 species of sharks that we have on the planet. Evidence indicates that, on the whole, and especially in a global context, we are doing quite well with managing most of these species. There have been some bumps in the road, but we have largely identified which species are at risk, and have taken actions to better protect them. 

However, not all Australian shark populations have been so lucky. And for these species, reversing the concerning conservation status will be a difficult battle. 

While not a direct population count, a recently published UQ-led study found that the numbers of (certain species of) hammerhead, tiger, white and whaler sharks caught in the Queensland Shark Control Program drastically declined by 74–92 per cent over the 55 years that the program has been in operation. 

Equally as worrying, the average size (total length) of the species investigated also decreased significantly, and the probability of capturing adult animals is down. There are compounding factors to studies that use fishing and shark-control programs as a proxy for population assessments, but the findings presented are so strong that the trends should not be ignored. 

"Despite all of the talk and sensationalism, shark bites remain extremely rare and unlikely events."

The task of counting sharks is fraught with difficulty, but a recent CSIRO-led study documented a new, cutting-edge methodology that, for the first time, provided a really compelling population assessment for large, highly migratory sharks. The study assessed the eastern and south-western Australian white shark populations (which rarely cross over) and estimated that there are likely to be around 750 and 1460 adult sharks in these populations, respectively. 

There is great optimism that the technique can be rolled out to develop baseline population counts for other species as well, and provide a foundation for assessing population trends of these sharks in the future.

Major pressures on shark populations include legal and illegal fishing, habitat degradation, marine debris and shark control programs. Despite all of the talk and sensationalism, shark bites remain extremely rare and unlikely events. Yet, Australia employs a wide range of lethal and non-lethal mitigation measures.

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