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Behavior

Shark attack prevention: what works, what doesn’t?

Sorry Spielberg, Jaws isn’t reality

The stereotypical public perception of shark attacks can pretty much be summed up with a movie like Jaws and its innumerable sequels; films like these portray sharks as ruthless creatures with no other motivation than just eating anything in their field of view. The media tends to follow this trend of portraying sharks as monsters to create sensational headlines that feed the fear of shark attacks, distracting us from the low probability of such attacks actually happening. So even though statistically, shark attacks on humans are incredibly unlikely, when attacks happen, they draw a ton of attention from the media. Rather than feed into the media frenzy about attacks, let’s take a look at some scientifically vetted evidence suggesting the best ways to prevent shark attacks; effective preventive measures need to be focused on education and changing the human perception of sharks, rather than quick policies that affect the environment in counterproductive ways.

Great white shark (Carcharodon carcharias) in its natural habitat (left), compared to “Bruce”, the great white shark from the movie Jaws (right). This image is a great contrast of truth vs. fiction, demonstrating how sharks are portrayed as aggressive animals in media and film rather than as peaceful swimmers in the wild. Photo credit: George T. Probst and Universal Studios

Great white shark (Carcharodon carcharias) in its natural habitat (left), compared to “Bruce”, the great white shark from the movie Jaws (right). This image is a great contrast of truth vs. fiction, demonstrating how sharks are portrayed as aggressive animals in media and film rather than as peaceful swimmers in the wild. Photo credit: George T. Probst and Universal Studios

 

Lethal strategies just don’t cut it

Unfortunately for sharks, lethal strategies are often the go-to method to prevent or address an attack and protect humans from sharks in their own habitat. Shark nets and drumlines (baited hooks) have historically been used as protective measures to minimize human-shark interactions. The most recent shark control program went on from 2013-2014 in Western Australia, using baited hooks to capture and kill sharks. However, the effectiveness of this kind of program has not been consistently proven in data; it’s expensive, and can greatly affect other marine organisms that get caught in the nets, not to mention wholly changing the ecology and migration patterns of sharks. In contrast, research by Simpfendorfer and colleagues found no decrease in population of tiger sharks in the area through years of the program taking place; they analyzed data from tiger sharks caught in the protective meshing program in Townsville, Australia from 1960s-1980s to come to this conclusion. As well, tracking studies in Hawaii, by Holland and colleagues, have shown tiger sharks have high mobility and large home ranges, which means sharks at a particular area one day would most likely not be the same sharks the next day. It would take an extraordinay amount of killing to even begin reducing shark populations in the area of a hypothetical attack, and looking for the shark responsible for the attack would most likely be unsuccessful. This is an example of why understanding the biology of sharks is important to the implementation of policies; there is no point throwing tax dollars away on nets, drumlines, or culls to prevent or address attacks when they don’t actually change attack risk in a given area.

net_impacts

Thresher shark (Alopias vulpinus) caught in a fishing net in Mexico. Nets like these are used in protective meshing programs such as the Western Australian Shark control program, and many times kill marine life trapped in them, including bycatch. Photo credit: Brian Skerry.

Turtle_in_net

Fishing nets impact many other marine animals besides the sharks targeted on the control programs. Image shows Hawksbill Turtle (Eretmochelys imbricata) caught in a fishing net in Jamaica. Photo credit: Mary Veira/Jamaica Environment Trust.

Biology-based strategies: better for everyone

A good example of successful mitigation programs, as described by Hazin and Chapman, comes from Brazil; here a seasonal ban on surfing in high risk beaches was implemented, decreasing exposure of humans to high risk areas during peak shark densities. Surfers in Brazil have been implicated in 52.7% of shark bites since 1992, however, after the ban on surfing activities, shark attack frequency decreased to 29.7%, showing to be a fairly succesful method of bite control.They also implemented a relocation program consisting of capturing sharks with baited longlines and transporting possibly threatening sharks away from shore, while releasing non-threatening sharks and bycatch (non-target species captured incidentaly) at site of capture. This strategy decreases damage to bycatch and unnecessary lethal strategies for non-threatening sharks. New technology, such as a magnetic barriers used to repell sharks from beach areas, called sharksafe barriers, have been tested by scientists such as Dr. Craig O’Connell, and have proven to have no effect on the behaviour of other animals that hang out in a given area. However, the barriers altered the behaviour of white sharks, manipulating their swimming patterns and reducing their presence near the barrier, proving to be a good eco-friendly replacement for nets, pending further testing.

great-white-shark-wants-hug-1

Great white shark (Carcharodon carcharias) swimming peacefully in the wild. Happy sharks= Healthy oceans! Photo credit: George T. Probst

Read the writing on the wall: common sense and being good neighbors can prevent shark attacks

To let go of the stigma that sharks are man-eating killers, it’s important to understand their biology and how we affect their behaviour so we can do our best to prevent being exposed to danger. Chapman and colleagues hypothesised that unprovoked bites are most likely caused by a disruption to the natural conditions of an area. For us, this means we can help ourselves stay safe while using coastal waters by ensuring we work towards sustainable fisheries policies, leaving enough prey for sharks in the area. Research by Werry and colleagues has also shown that rainfall alters swimming patterns of bull sharks and might push them to feed near coastal areas close to rivers; again, we should take heed of biological evidence like this and avoid river mouths after a rainfall. More generally, climate, water quality, and fisheries health are all affected by human actions, so it’s a priority to understand our role as ocean users and the importance of coexistence. The implementation of effective programs backed up by education to the public will not only help reduce the risk of human deaths, but will also save shark populations from declining more in the future. Happy sharks + happy humans = healthier oceans is a goal we can all strive for!

This article is a review of the papers found here, here, here, here, here and here.

Discussion

2 Responses to “Shark attack prevention: what works, what doesn’t?”

  1. Great article Karla, people need to be reminded of this constantly. Sharks are far from harmless, but they are not “out together us” either.

    Posted by Wayne Heinze | April 8, 2017, 5:17 pm
    • Hello Wayne! Apologies for the late reply. Thank you for reading! It is extremely important for people that are not so immersed in the marine science world to understand their impact on species survival; because of course sharks are not harmless! and that is why we must focus on educating the general public. It is really easy to vilify animals that are natural predators when you don’t understand them.

      Posted by Karla Haiat | April 14, 2017, 9:11 am

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