Sharks And Noise Pollution: Impact And Consequences

Noise pollution is a growing concern for marine life, and sharks are no exception. Sharks are highly sensitive to sound, and noise pollution can have a significant impact on their behaviour and survival. While some frequencies can attract sharks, loud and irregular noises often cause them to withdraw. This can affect their ability to locate prey, communicate, and detect predators. With the increase in human activities such as transportation, oil and gas exploration, and construction, the noise levels in our oceans are rising, and it is crucial to understand the impact on shark populations.

Sharks' hearing range is sensitive to low-frequency sounds, which overlaps with most anthropogenic noise

Sharks have a very well-developed sense of hearing and are able to detect sounds from several kilometres away. They are particularly sensitive to very low-frequency sounds, with a peak in perception between 200 and 600 Hz. This hearing range overlaps with most of the anthropogenic sound produced by seismic airgun arrays, dredging, pile driving and shipping.

Anthropogenic noise can be extremely damaging to sharks. At the lowest level, extensive background noise from boat motors or offshore wind farms, even at relatively low volumes, can cause increased stress to marine life or mask their sounds, which are critical for survival. Noises from underwater explosions can cause temporary or permanent deafness.

Anthropogenic noise can also alter shark behaviour. A study found that sharks approached baited underwater cameras less frequently when exposed to artificial and orca sounds. The sharks also displayed fewer inquisitive interactions and took longer to arrive at the food source. These findings suggest that anthropogenic noise may repel sharks from food-rich habitats, potentially shifting their natural ranges and seriously impacting their health.

The impact of anthropogenic noise on sharks is a cause for concern, especially given the worldwide increase in such noise and the drastic population decline in many shark species.

Anthropogenic noise can cause stress, tissue damage, hearing loss, and even death in sharks

Anthropogenic noise can have a range of harmful effects on sharks, from causing stress and behavioural changes to tissue damage, hearing loss, and even death.

Stress and Behavioural Changes

Anthropogenic noise can cause stress and alter the behaviour of sharks. For example, noise can disrupt their natural behaviours, such as feeding, socialising, and moving within their habitat. It can also affect their ability to detect prey, communicate, and avoid predators. In addition, noise can mask important biological sounds, such as those used for communication, finding prey, and detecting predators.

Tissue Damage and Hearing Loss

Anthropogenic noise, especially from loud sources like underwater explosions, can cause temporary or permanent hearing loss in sharks. This is because the noise can destroy the sensitive sensory tissues in the inner ear and lateral line systems of sharks. In extreme cases, hearing loss can lead to death if sharks lose their ability to hear or detect hydrodynamic changes in their environment.

Death

Anthropogenic noise can also lead to the death of sharks, either indirectly through the effects of stress and hearing loss or directly through tissue damage. The impact of noise on sharks can vary depending on the species and their migratory habits. Some shark species, such as great whites, tigers, and whale sharks, are migratory and can potentially leave disturbed areas. However, most shark species, such as wobbegong, bamboo, and Port Jackson sharks, remain in a single location or change habitats only during specific life stages. These sedentary species are particularly vulnerable to noise pollution, as they are less likely to leave during high-intensity sound events.

Noise pollution can mask biologically essential sounds for sharks, such as those used for communication, finding prey, and detecting predators

Noise pollution can have a detrimental impact on sharks, masking biologically essential sounds and affecting their ability to communicate, find prey, and detect predators. Sharks are sensitive to sound, with a well-developed sense of hearing that can detect sounds from kilometres away. They rely on certain frequencies for various behaviours, and noise pollution can disrupt these frequencies.

Anthropogenic noise, or human-generated noise, can be especially harmful to sharks as it can interfere with their ability to perceive important biological sounds. This includes sounds used for communication, finding prey, and detecting predators. For example, reef and coastal sharks were found to be less numerous in an area, with fewer interactions and reduced inquisitive behaviour when exposed to anthropogenic noise.

Additionally, noise pollution can cause stress and mask critical biological sounds, further impacting the survival of sharks. The impact of noise pollution on sharks is a growing concern, particularly in areas with high levels of human activity, such as transportation and energy exploration and exploitation.

The effects of noise pollution on sharks are complex and vary among species. Some sharks, such as great whites, tigers, and whale sharks, are migratory and can leave disturbed areas. However, most shark species, like wobbegong, bamboo, and Port Jackson sharks, remain in a single location or change habitats only during specific life stages. These sedentary sharks are more vulnerable to the impacts of noise pollution.

Further research is needed to understand the specific effects of different types and intensities of noise on shark behaviour and to inform management practices and policies to mitigate the impacts of noise pollution on shark populations.

Noise pollution can alter shark behaviour, including feeding, socialising, and movement patterns

Noise pollution can significantly alter shark behaviour, including feeding, socialising, and movement patterns.

Sharks are highly sensitive to noise pollution, which can impact their predatory responses. Low-frequency sounds tend to attract sharks, while sharp, high-frequency sounds cause them to withdraw. This is particularly true for sharks that occupy a single location or patch of reef, such as wobbegong, bamboo, and Port Jackson sharks.

Research has shown that noise pollution can cause sharks to alter their feeding behaviour, social interactions, and movement patterns. For example, a study conducted in Western Australia found that when exposed to artificial sounds, sharks approached baited canisters less frequently and exhibited fewer inquisitive interactions. Additionally, they were slower to arrive at the food source.

Noise pollution can also affect the ability of sharks to locate prey and navigate their environment. This is because sound waves travel more easily through ocean environments, and sharks are sensitive to underwater vibrations and sounds.

Furthermore, noise pollution can be a source of stress for sharks, affecting their behavioural and sensory functions. It can also mask important biological sounds, such as those used for communication, finding prey, and detecting predators.

Overall, noise pollution has been shown to have significant effects on shark behaviour, including feeding, socialising, and movement patterns. These impacts can vary depending on the species and the type of noise. More research is needed to fully understand the effects of noise pollution on shark populations and to inform management practices and policies.

Some shark species are more vulnerable to noise pollution due to their sedentary nature and sensitivity to specific frequencies

Sharks have a very narrow hearing range compared to marine mammals, but they are particularly sensitive to very low frequencies. This hearing range overlaps with most of the anthropogenic sound produced by seismic airgun arrays, dredging, pile driving, and shipping. While some shark species like great whites, tigers, and whale sharks are migratory and can leave a disturbed area, most shark species are sedentary and remain in a single location or patch of reef. These sedentary sharks are particularly vulnerable to sound pollution as they typically would not leave the area during a high-intensity sound event.

The effects of noise pollution on sharks can vary depending on the species and their sensitivity to specific frequencies. Wobbegong, bamboo, and Port Jackson sharks are examples of sedentary shark species that are more vulnerable to noise pollution. Wobbegong sharks, for instance, stay in a single location or patch of reef and only change habitats when they reach a critical part of their lifecycle. Similarly, bamboo sharks are known to occupy a small home range and show site fidelity, making them less likely to leave a noisy area. Port Jackson sharks also have a limited home range and tend to remain in the same area unless disturbed.

The sensitivity of shark species to specific frequencies has been studied, and it has been found that low-frequency and pulsed sounds tend to attract sharks, while loud and irregular noises elicit a withdrawal response. For example, a study found that silky sharks were attracted to low frequencies similar to the range at which a struggling fish would be heard, but they withdrew from loud and irregular noises. Lemon sharks were also observed to have a withdrawal response to the sudden onset of orca calls, broadband synthetic sounds, and 500 Hz pure tones.

The impact of noise pollution on sedentary shark species and their sensitivity to specific frequencies is an area of ongoing research. The Neuroecology Group, part of the UWA Oceans Institute and School of Animal Biology, is studying the effects of sounds on sharks, including assessing their sensitivity to different frequencies and intensities. This research aims to inform management practices and policies to protect vulnerable shark species from the detrimental effects of noise pollution.

Frequently asked questions