Shark nets: a false sense of security

Loéva Martin-Podevin, PhD candidate Macquarie University, Supervisors: Professor Culum Brown and Jane Williamson 

Sharks in Australia  

Australia is home to 180 shark species, representing almost half of all shark species worldwide. Most of the country’s human population is distributed along the coast, increasing the possibility of human-shark interactions. Recently, these interactions have been on the rise worldwide¹ attributed to the increase in coastal population density and the growing number of people participating in water activities (surfing, diving, swimming). Human-shark interactions are defined as any contact between a human and a shark, ranging from a shark swimming close to a human to a shark bite related death. These interactions can be divided into provoked or unprovoked. A provoked incident occurs when a human actively tries to engage with a shark. For example, when a diver approaches too close or tries to touch the shark and gets bitten. The probability of getting killed by a shark in Australia is very low: one in 8 million, the same as being killed by a kangaroo (The Nature Conservancy Australia). In 2023, 15 unprovoked shark incidents were reported in Australia, (including one in New South Wales (NSW)) which resulted in four fatalities. Shark bites most likely occur because sharks mistake humans for prey. But they soon realise their mistake and move on. Humans are not on their menu. Three species of sharks are mostly responsible for these incidents: The White Shark, the Bull Shark and the Tiger Shark. These species are the targets of shark management methods on Australia’s East Coast.   

Sharks: the key to a healthy ocean   

Sharks are not the human-eating monsters depicted in the movie ‘Jaws’. They are intelligent and sentient animals with different personalities². Just like us, some sharks are more aggressive and others are more shy. A healthy ocean is an ocean with sharks. As apex predators (top of the food chain), large shark species maintain a balanced ecosystem by keeping the prey populations stable. If you remove sharks, prey populations will increase and over-eat lower species in the food chain such as plants, creating an imbalanced ecosystem. They also help maintain genetically strong prey populations by eating weak and sick fish. Despite their resilience in surviving mass extinction events over millions of years, sharks are currently facing major threats including overfishing, bycatch, habitat destruction and climate change. Since 1970, the global abundance of oceanic sharks and rays has declined by 71%³. Sharks are mainly targeted for their fins which are used for soup, a delicacy in Asia. During this process, sharks are caught, their fins are sliced off and their body is thrown back into the Ocean. The shark only dies after being eaten by other animals, blood loss or by drowning as they are required to swim to force water through their gills to breathe.  

Shark nets: a lethal method  

In 1937, the Shark Meshing Program (SMP) also known as the Bather Protection Program started, deploying fishing nets each year to prevent sharks from swimming too close to the beach. The nets are 150m long and 6m deep and are placed 4 meters below the surface. These shark nets have been installed at 51 of the most popular beaches across Southern NSW. The goal was to catch the target sharks in the nets and kill them. However, sharks can swim around the net as most beaches are longer than 150 meters. They can swim below and above the net as they are not fixed to the seafloor or the surface. Approximately 40% of sharks entangled in nets are caught on the beach side of the net, indicating that they have swum around to get to the beach and are caught on their way back to the open ocean. Scientists investigated whether there was a lower probability of shark interactions at netted beaches versus non-netted beaches⁴. Dr Huveneers and his team found the same interaction rate at both netted and non-netted beaches. This raises concerns about the actual effectiveness of the nets in protecting beachgoers. If sharks can easily avoid the nets and the chance of encountering a shark is not reduced, these nets provide nothing more than a false sense of security.   

Nets kill endangered species  

Shark nets are not specifically designed to target sharks, they catch a wide range of non-target and endangered species. The performance report published by the NSW Department of Primary Industries (DPI) revealed that for the 2022-2023 season: shark nets caught 228 animals, with 24 target sharks (11%) and 204 non-target animals (89%) including 120 sharks, 58 rays, 14 turtles and 10 marine mammals. As many as 143 animals (63%) died in the nets. Recently, Humane Society International Australia announced that for the 2023-2024 season: 208 non-target animals (93%) were caught in shark nets, including charismatic species such as whales, turtles, rays, dolphins and smaller species of sharks. Within those, 134 animals were found dead in the nets (64%) including 5 Critically Endangered Grey Nurse Sharks, 4 Endangered Leatherback Turtles and 1 Endangered Loggerhead Turtle. Each year, the same observations are made: most animals caught in nets are non-target species that die entangled. Protecting these vulnerable marine species is essential for conserving our marine ecosystems.  

Shark management future: new technologies  

Shark nets do not protect us and they kill an alarming number of non-target and endangered animals. We need non-lethal shark management methods to mitigate the rising number of human-shark interactions. NSW invested $85.6 million in 2022-2026 in new technologies for the Shark Management Program⁵.  Since 2016, several new technologies have been trialed around NSW including drones, SMART drumlines, listening stations and personal deterrents. SMART drumlines use a baited hook. If the shark bites, it triggers a magnet and sends a signal to a contractor to check the drumline in the next 30 minutes to tag and release the shark further away. This method results in very low mortality and bycatch compared to shark nets. It also allows us to track the movements of sharks using listening stations. These devices are placed near beaches to detect if a tagged shark swims within 500 meters and send a notification through the SharkSmart App to inform the public. Drones are the public’s favourite management method as they can easily spot sharks swimming nearby and beachgoers are warned to get out of the water. Another technology available for surfers is the use of personal deterrents. They emit signals that interfere with the unique electro-sensory system of sharks, scaring them away. All NSW councils agree on removing shark nets and using a combination of new technologies instead. Last year, the NSW State government resisted calls to end the use of shark nets, claiming more data was needed before they could alter the program. The science is clear: shark nets do not protect the public, despite taking a terrible toll on marine wildlife. We are hoping that in the coming years, nets will be removed allowing us to protect our beautiful and unique Australian marine wildlife.   

Sources: 

1. Bradshaw, C.J.A., et al., Predicting potential future reduction in shark bites on people. Royal Society Open Science, 2021. 8(3). 
2. Brown, C. and V. Schluessel, Smart sharks: a review of chondrichthyan cognition. Animal Cognition, 2023. 26(1): p. 175-188. 
3. Pacoureau, N., et al., Half a century of global decline in oceanic sharks and rays. Nature, 2021. 589(7843): p. 567-571. 
4. Huveneers, C., et al., Shifts in the incidence of shark bites and efficacy of beach-focussed mitigation in Australia. Marine Pollution Bulletin, 2024. 198: p. 115855. 
5. Peden, A.E. and R.W. Brander, Is further investment in shark management in New South Wales worthwhile? Surfer views on coastal public health issues. Australian and New Zealand journal of public health, 2024: p. 100116.