Are There Really More Sharks?
If you see more sharks, does it mean there are more sharks? The short answer is not necessarily.
Sharks have a special place in the human psyche, sparking equal wonder and fear. But this can understandably cloud our judgement of an animal critical to the health of our oceans.
If you see more sharks, does it mean there are more sharks? The short answer is not necessarily, and several reasons exist.
But first, some context to shark populations in Australia is needed.
Shark Populations in Australia: A Complex Picture
In Australia, shark fishing peaked in the early 2000s, and today, around one in eight species of shark and ray in Australian waters are threatened with extinction¹. Of the 331 species of sharks and rays in our waters, around 180 of them are sharks and generally speaking, their reproductive rate is slow². On average, a shark matures at 10 years old and birthing four to six pups every two to three years³. However, for some at the extremes, like the dusky shark, female maturity is from 27 years with a two-year pregnancy plus a year’s rest between producing 3-18 pups¹. Some sharks are simply more vulnerable to fishing pressure than others, and you can see how quickly their numbers drop and the many years or even decades for them to return.
Improved Fisheries Management: Progress but More to Do
Since the early 2000s, Australia’s management of its commercial fisheries with respect to sharks has greatly improved (still much to do though!), thanks to conservation efforts, scientists and numerous governments⁴. As a consequence, we have seen some species stabilise, like duskies in north-west WA⁵, or blacktip sharks only recently recovering to near original numbers since massive amounts were legally fished in the 70s to early 90s⁶. However, as we now know, not all 180-odd types of sharks are built equally, and they vary in their reproductive rate.
Why Are We Seeing More Sharks?
- Warming Oceans and Changing Habitats
- Sharks Learning New Behaviours
- Social Media and the Availability Bias
Changes in fishing pressure, different reproductive rates, some evidence of population recovery in certain species, and a mix of anecdotal reports down at the boat ramp can seem overwhelming and confusing! Let’s explore three reasons why seeing more sharks doesn’t necessarily mean more: warming oceans, a shark’s ability to learn, and social media!
Warming oceans are changing where species move and how long they hang around for in certain areas – so you could see more sharks in certain places more often (possibly for longer) or even in places sharks never or rarely go to. In the famous case of bull sharks that love water temps in the low 20s Celsius, they are moving further south as the East Australian Current gets stronger, pushing warm tropical water southwards from Queensland through to Victoria and Tasmania⁷. In fact, earlier this year a bull shark was spotted in the Mitchell River in eastern Victoria. In short, there’s potential for greater overlap in human activities where sharks have previously not or rarely been encountered.
Getting ‘sharked’ is probably one the most frustrating things for a fisher. Known formally as ‘depredation’ it’s when a shark takes the fish off the end of your hook leaving you with little or no fish at all. Not ideal when it may be the only fish you ‘catch’ all day! Depredation is a real phenomenon known to occur particularly in areas popular with fishers⁸⁹. Much like a dog, we’ve unintentionally trained them for an easy feed as sharks can associate the sound of a boat engine or a fish’s struggle as a sign of an easy meal on offer. Depredation rates can be as high as 40% of trips in some places⁸, and it’s no wonder the first conclusion is, “There are heaps of sharks, it wasn’t like this 5 or 10 years ago!” But when you think of free pizza, your perspective changes. If I walked down the same street every day offering free pizza, I might get a few people in the first week but eventually, word is going to get out and, in a few weeks, later or sooner, I’m regularly swarmed by a crowd. I see many more people, and I interact with many more people, but I can’t say that the population of Australia is booming. So yes, fishers are likely to see more sharks in their regular fishing spots than before, but that specific area doesn’t necessarily reflect the whole population.
A cognitive bias we all have as humans is the ‘availability bias’ – the more something readily comes to mind and the stronger it evokes an emotional response, the more common we think it is. You read ‘shark’ and already there’s an image of a great white, mouth opened, forming in your mind and a bit of a shudder going down your spine. Couple that with an astonishing volume of social media content and traditional media reporting of sharks, and it’s a perfect recipe for the availability bias to kick in. So, when you see more and hear more, it’s easy to lose sight of the raw numbers and cold facts that tell a different story, or at the least, ground a story with necessary context.
The Issue of Depredation
Depredation is certainly an evolving issue though, and one that doesn’t benefit anyone, apart from perhaps the shark getting an easy meal. Many research projects are underway to better understand which species are responsible, how often and where it is occurring, and what can be done to mitigate these risks.
The Call for Targeted Shark Fishing
Fishers often first call for an increase in targeted shark fishing. While some shark species can handle well-managed take, other more vulnerable species, like hammerhead sharks, are often caught as bycatch, particularly in gillnet fisheries. In many cases, much remains to be done to ensure that these more vulnerable shark species are given every opportunity to recover from historic overfishing.
The Path Forward: Conservation and Sustainability
As we improve our conservation efforts for an animal that keeps marine food webs healthy, we hope that our threatened species can recover and that currently healthy populations remain stable. For species numbers that are trending upward, we have to remember that this often comes off a historical low. Directed efforts towards species-specific shark population assessments can tell us how many individuals of a species there are, where they are and why they move the way they do – unfortunately, this information is lacking for many species. Nonetheless, addressing these gaps provides us with a better and more effective sense of how our fishery management is working (or not), and the opportunity to avoid certain areas that may feel unsafe or negatively impact the fishing experience.
Globally and in Australia, the recovery of endangered shark species and the environmental sustainability of our fisheries has never been more crucial. When it comes to sharks, we are their biggest threat but also their only hope.
References:
- Kyne PM, Heupel MR, White WT, Simpfendorfer CA (2021) ‘The Action Plan for Australian Sharks and Rays 2021.’ (NESP Marine Biodiversity Hub: Hobart)
- Simpfendorfer CA, Rigby CL (2023) ‘A Report Card for Australia’s Sharks and Rays.’ (University of Tasmania; Fisheries Research and Development Corporation: Australia)
- Heupel MR, Kyne PM, White WT, Simpfendorfer CA (2019) Shark Action Plan Policy Report. report NESP Marine Biodiversity Hub, Available at http://epubs.aims.gov.au//handle/11068/15377 [Verified 18 August 2020]
- Wright D, Davis K, Blake S, Emery TJ, D’Alberto B, Woodhams J (2022) Shark Assessment Report 2022. Australian Bureau of Agricultural and Resource Economics and Sciences, Australia. Available at https://www.agriculture.gov.au/abares/research-topics/fisheries/fisheries-research/shark-assessment-report-2022#download-the-full-report [Verified 21 February 2025]
- Braccini M, Molony B, Blay N (2020) ‘Patterns in abundance and size of sharks in northwestern Australia: cause for optimism’ ICES Journal of Marine Science 77, 72–82. doi:10.1093/icesjms/fsz187
- Usher M, Braccini M, Roelofs A, Peddemors V (2020) Australian Blacktip Shark 2020. Fisheries Research and Development Corporation, Australia. Available at https://www.fish.gov.au/report/416-Australian-Blacktip-Shark-2020 [Verified 30 May 2022]
- Niella Y, Smoothey AF, Peddemors V, Harcourt R (2020) ‘Predicting changes in distribution of a large coastal shark in the face of the strengthening East Australian Current’ Marine Ecology Progress Series 642, 163–177. doi:10.3354/meps13322
- Mitchell J, Mclean D, Collin S, Taylor S, Jackson G, Fisher R, Langlois T (2017) ‘Quantifying shark depredation in a recreational fishery in the Ningaloo Marine Park and Exmouth Gulf, Western Australia’ Marine Ecology Progress Series 587,. doi:10.3354/meps12412
- Mitchell JD, Camilieri-Asch V, Jaine FRA, Peddemors VM, Langlois TJ (2021) ‘Galapagos shark movement patterns and interactions with fishing vessels in the marine parks surrounding Lord Howe Island: A report for Parks Australia.’ (Parks Australia, Australian Government: Australia) Available at https://parksaustralia.gov.au/marine/pub/scientific-publications/Finalupdated_LordHoweMPGalapagossharkreportforParksAustralia.pdf [Verified 21 February 2025]