Sharks And Noise: Understanding The Impact Of Underwater Noises

Sharks are sensitive to noise pollution. They possess an inner ear and a lateral line, which are sensitive to underwater vibrations and sounds. While they have a narrow hearing range, they are particularly sensitive to very low frequencies. This range overlaps with most of the anthropogenic sound produced by seismic airgun arrays, dredging, pile driving and shipping.

Noise pollution can impact sharks in several ways. It can affect their ability to determine prey location and accessibility, as well as their mating, communication, and predator-prey activities. It can also be a source of acute or chronic stress, which may further affect their behavioural and sensory functions. Additionally, loud noises can mask important biological sounds, which are essential for communication, finding prey and mates, and detecting predators.

Research has shown that noise pollution can alter the behaviour of sharks. For example, a study found that reef and coastal sharks were less present in an area when two sets of sounds (orca calls and artificial noise) were playing. The artificial sound also delayed their arrival time to a food source. Another study found that low frequencies elicited attractive responses from sharks, while sharp, high frequencies elicited withdrawals.

Noise pollution, therefore, has the potential to significantly impact shark behaviour and their natural habitats.

Sharks' hearing range overlaps with most anthropogenic noise

Sharks are sensitive to noise pollution, and their hearing range overlaps with most anthropogenic noise. Anthropogenic noise is human-generated noise, which can be purposeful or accidental. This noise is particularly harmful to sharks as they are sensitive to sound waves and rely on certain frequencies for mating, communication, and predator-prey interactions. Furthermore, sound waves travel about four times faster in the ocean than in the air.

Sharks' hearing range is narrow compared to marine mammals, but they are sensitive to very low frequencies. This range overlaps with most anthropogenic sound produced by seismic airgun arrays, dredging, pile driving, and shipping. Noise from these sources can impact the ability of sharks to locate prey and perform other behaviours.

While some shark species are migratory and can leave disturbed areas, such as great whites, tigers, and whale sharks, most species, like wobbegong, bamboo, and Port Jackson sharks, remain in a single location or patch of reef. Sound pollution is a particular threat to these sedentary sharks, as they typically do not leave the area during high-intensity sound events.

Research has shown that noise pollution can alter the behaviour of sharks. For example, a study by Chapuis et al. in 2018 found that reef and coastal sharks, such as grey reef sharks or lemon sharks, were less present in an area when sounds were played. The few sharks that remained interacted less and less aggressively with the experimental rig. Additionally, great white sharks arrived late and left quickly when artificial sounds were played.

The impact of noise pollution on sharks is a growing concern, especially with the increasing amount of man-made noise in the ocean from shipping, building, and oil and gas surveys. More research is needed to understand the effects of noise pollution on sharks and inform management practices and policies.

Noise pollution can cause stress and mask important biological sounds

Noise pollution can have a detrimental impact on sharks, causing stress and masking important biological sounds. As air-breathing humans, we are somewhat shielded from the full intensity of the noise we produce underwater. However, for sharks and other marine life, the effects can be significant.

Anthropogenic noise, or human-generated noise, can be especially harmful to sharks for two key reasons. Firstly, sharks are highly sensitive to sound waves and rely on certain frequencies for various essential activities, such as mating, communication, and predator-prey interactions. Secondly, sound waves travel much more efficiently through water, approximately four times more so than through air. This means that the noise generated by human activities, such as deep-sea drilling and shipping, can have far-reaching consequences for sharks and other marine organisms.

Noise pollution can cause stress and disrupt vital biological functions in sharks. It can interfere with their ability to locate prey, communicate with their own species, and detect predators. The impact of noise is further exacerbated by the fact that some shark species are sedentary or have limited migration patterns, such as wobbegong, bamboo, and Port Jackson sharks. These sharks typically remain in a specific location or move between small patches of reef, making them more vulnerable to the effects of noise pollution in their habitat.

Additionally, noise pollution can mask important biological sounds that are essential for the survival and well-being of sharks. The loud sounds produced by human activities can drown out the lower-frequency sounds that sharks are particularly sensitive to, such as those produced by struggling prey or the hydrodynamic changes caused by swimming predators. This disruption can impair the sharks' ability to navigate their environment effectively, find food, and avoid threats.

Research has shown that noise pollution can alter the behaviour of sharks. For example, a study by Chapuis et al. in 2018 found that reef and coastal sharks, such as grey reef sharks and lemon sharks, were less likely to approach an area when orca calls or artificial sounds were played. The sharks that remained in the area displayed reduced inquisitiveness and interacted less aggressively with the research equipment.

In conclusion, noise pollution has the potential to cause stress and mask critical biological sounds for sharks. The impact of anthropogenic noise on shark behaviour and physiology underscores the need for further research and the development of effective conservation strategies to mitigate these harmful effects.

Low frequencies attract sharks, while loud and irregular noises cause withdrawal

Sharks are sensitive to underwater vibrations and sounds. They are attracted to low-frequency sounds, particularly those in the 20 to 60 Hz range, which are similar to the sounds made by struggling fish. However, they are deterred by loud and irregular noises, which cause a withdrawal response.

The Effects of Noise Pollution on Sharks

Noise pollution in the ocean is primarily caused by human activities such as transportation, oil and gas exploration, and construction. This added background noise can have detrimental effects on sharks and other marine life. Extremely loud noises can damage the sensory tissues in the inner ear and lateral line systems of fishes, leading to hearing loss or death.

Noise pollution can also cause acute or chronic stress in sharks, affecting their behavioural and sensory functions. Additionally, loud sounds can mask important biological sounds, such as those used for communication, finding prey, and detecting predators.

Shark Species and Noise Sensitivity

There are over 100 species of sharks and rays in Western Australian waters, including the pygmy shark and the whale shark. Some shark species, such as great whites, tigers, and whale sharks, are migratory and can leave disturbed areas. However, most species, such as wobbegong, bamboo, and Port Jackson sharks, remain in a single location or patch of reef.

Noise pollution poses a particular threat to sedentary sharks, as they typically do not leave the area during high-intensity sound events. Research is being conducted to assess the sensitivity of different shark species to various frequencies and intensities of sound, as well as the potential overlap between ambient sounds and the auditory abilities of local shark populations.

Understanding Shark Behavioural Responses

It is important to study the behaviour of wild sharks and their responses to different types of noise pollution. This can help inform management practices and policies to protect shark populations and broaden the regulatory framework regarding noise pollution.

Anthropogenic noise can alter shark behaviour and deter them from food sources

Anthropogenic noise is human-generated noise, whether purposeful or accidental. It is particularly harmful in the ocean because many marine species are sensitive to sound waves and rely on certain frequencies for mating, communication, and predator-prey activities. Furthermore, sound waves travel about four times more easily through ocean environments than through air.

Sharks possess a well-developed sense of hearing and can detect sounds from several kilometres away. They can perceive sounds with a frequency between 20 Hz and 1.5 kHz, depending on the species, and are especially sensitive to low-frequency sounds, with a peak in perception between 200 and 600 Hz.

Research has shown that noise pollution can alter the behaviour of sharks. A study by Chapuis et al. in 2018 found that reef and coastal sharks, such as grey reef sharks or lemon sharks, were less likely to approach an area when two sets of sounds (orca calls and artificial noise) were played. The few sharks that remained in the area interacted less and less aggressively with the researchers' experimental rig.

The impact of anthropogenic noise on shark behaviour is concerning because there is an increasing amount of human-made noise in the ocean from sources such as shipping, building, and oil and gas surveys. If a small speaker can disrupt the behaviour of a reef shark, the blasts from seismic surveys could have even more significant effects.

Noise pollution may cause long-term shifts in sharks' natural ranges

Noise pollution can impact sharks' ability to determine prey location and accessibility, as well as other behaviours. Low frequencies elicit attractive responses from sharks, while sharp, high frequencies cause withdrawals. Noise from deep-sea drilling and shipping can therefore disrupt sharks' predatory responses.

Research has shown that noise pollution alters the behaviour of bony fish, and it is likely that it has a similar effect on sharks. Noise can cause increased stress, mask critical biological sounds, and even lead to temporary or permanent deafness. As noise pollution continues to increase in the ocean, it is important to study its effects on sharks and other marine life to inform management practices and policies.

Frequently asked questions