No evidence to support that shark nets and drumlines improve safety
We often hear claims from the New South Wales (NSW) and Queensland (QLD) governments defending their shark mitigation measures, that they are effective, followed by alleged "proof" in the form of numbers claiming that there have only been 3 fatalities since they’ve been introduced (Cardno 2019; SMP 2019/20; SMP 2020/21).
To the majority of the public, this seems to make sense because surely, if "not many" people have died at the beach with these control systems in place, then they must be keeping us safe, right? There are several flaws with this claim, which we will look at here.
Nets and drumlines cannot reduce the severity of incidents
Firstly, we need to decide if the rate of fatalities is the correct way to measure the effectiveness of shark nets and drumlines. Many factors determine if a shark bite is going to end up being fatal or not, medical response time, proximity to a hospital, shark species and many more variables, but nets and drumlines do not make the list. Given their intent is not to reduce the severity of shark bites, and there is no way for them to do so, it is widely accepted that their aim is to reduce or eliminate shark bites - so we should look at all shark incidents, not just fatalities, to assess their efficacy.
Advancements in medical care
Advancements in medical care and quicker access to treatment have made a significant impact in decreasing the rate of fatal shark bites (Ricci, Vargas, Singhal, & Lee 2016, p. 112, as cited in Gibbs, Fetterplace, Rees & Hanich, 2019). Regarding shark bite incidents in Sydney in 2009, Rtshiladze, Andersen, Nguyen, Grabs, and Ho, note in the ANZ Journal of Surgery (2011, p. 350 as cited in Gibbs et al) that:
"Recent advances in the management of major trauma patients has led to a greater understanding of the role of pre‐hospital tourniquets, rapid transit to the operating suite and damage control surgery."
There have been many non-fatal incidents at beaches with nets and drumlines—the recorded number being 63 non-fatal encounters, out of a total of 66 incidents, between NSW and QLD (Cardno 2019; SMP 2019/20; SMP 2020/21). The data available also shows that there is no statistical difference in the numbers of shark bites between beaches with and without shark control equipment (Australian Shark Incident Database).
Shark related fatalities in decline
From 1836 to 2019, there were 217 shark-related incidents on QLD beaches, 51 of which were fatal. Looking at the data visualised in the graph below we can see the red trendline showing fatal incidents, peaking in the late 1930s and then steadily dropping over the decades. This is despite the number of overall incidents rising over the years as a consequence of exponential population growth. (Australian Shark Incident Database)
There’s a lot to take in from this data besides the decline in fatalities. Even though the number of incidents have increased, as QLD’s population has increased exponentially from 1.03 million in 1940 to 5.1 million currently (roughly 5x), it remains a testament to how little sharks are paying attention to us. The number of incidents have only doubled and not multiplied by 5.
Fatalities remain a poor indicator of safety
There are many other, often complex, factors affecting the number of shark incidents overall which we discuss in other places, but fatalities themselves remain a poor indicator of safety because medical expertise, techniques, and knowledge have all increased dramatically since the 1930s. This, along with the excellent work done by Surf Life Savers (also present at nearly all beaches that the government implements shark control equipment) means that we are simply better at saving people’s lives if they are involved in an incident, rather than preventing shark incidents, to begin with. The data clearly shows this.
The data also shows no drop in fatalities or incidents at the point shark control measures were introduced. Had they made a difference, the data would give us evidence of it. Yet it does not - trends in both fatalities and overall incidents do not show any significant pattern over the years in response to the introduction of these measures.
Nets and drumlines do not improve safety
As scientists, statistical significance is key to confirming whether or not something is having an effect. In this case, due to the nature of incidents, including fatal ones, the improved medical care we are capable of, and the rarity of shark incidents overall, there is simply no evidence that nets and drumlines have made any improvement in safety since their deployment in both QLD and NSW.
References and further information
Australian Shark Incident Database (n.d.), Taronga Conservation Society Australia, https://www.taronga.org.au/conservation-and-science/australian-shark-incident-database
Cardno (2019), Queensland Shark Control Program: Review of Alternative Approaches, prepared for Queensland Department of Agriculture and Fisheries, September, Author Craig Blount, Cardno NSW/ACT, Australia, accessed online, https://www.publications.qld.gov.au/dataset/e20e6bcd-c076-42a2-9e17-7d549b02254e/resource/76358bc5-a2fa-46ce-a8cb-0891c75e971a/download/qld-shark-control-program-review-alternative-approaches.pdf, accessed via https://www.publications.qld.gov.au/dataset/queensland-shark-control-program/resource/76358bc5-a2fa-46ce-a8cb-0891c75e971a
Gibbs, L ., Fetterplace, L., Rees, M., Hanich, Q., (2019), Effects and effectiveness of lethal shark hazard management: The Shark Meshing (Bather Protection) Program, NSW, Australia, accessed online, https://besjournals.onlinelibrary.wiley.com/doi/full/10.1002/pan3.10063
SMP (2019/20), Shark Meshing (Bather Protection) Program 2019/20 Annual Performance Report, Prepared in accordance with the 2017 Joint Management Agreement and Associated Management Plan, Published by NSW Department of PrimaryIndustries, accessed online, https://www.sharksmart.nsw.gov.au/__data/assets/pdf_file/0009/1246275/smp-2019-2020-annual-performance-report.pdf
SMP (2020/21), Shark Meshing (Bather Protection) Program 2019/20 Annual Performance Report, Prepared in accordance with the 2017 Joint Management Agreement and Associated Management Plan, Published by NSW Department of PrimaryIndustries, accessed online, https://www.sharksmart.nsw.gov.au/__data/assets/pdf_file/0009/1325880/SMP-2020-21-Annual-Performance-Report.pdf