Frequently Asked Questions

The concept of bioacoustics dates back to Aristotle (Lynch 2022), who first noted that fish make sounds. However, it wasn't until World War II that scientists made significant advancements. During the war, submarines used sonar technology to detect enemy vessels. Sounds that seemed to be enemy ships or submarines frequently alarmed sonar technicians, however, they eventually realized that the ocean was full of natural sounds.

From 1948 to 1970, marine biologist Marie Fish and engineer William Mowbray worked with the U.S. Navy to distinguish biological sounds from submarines (Goldfarb 2021). They published articles and a foundational book on fish sounds, establishing the basis for fish bioacoustics. However, almost all of these recordings were obtained from captive fish undergoing various unnatural stimuli. While these told us that these species could make sounds, they did not necessarily document natural sounds. Few of the sounds they documented have actually been confirmed from nature.
Recent studies show that as many as 80% of all bony fish species likely use sounds to communicate (Looby 2023). That’s at least 20,000 species. If you drop a hydrophone (an underwater microphone) in almost any natural fish environment, you will hear myriad sounds in the 100 Hz - 2.5 kHz range that are likely to be fish sounds. However, if there are more than one species present, it is exceedingly difficult to tell which species made each sound. Fish don’t open their mouths to call and they rarely have conspicuous movements that show you which is making the sound. Fish sounds are not difficult to record, but they are difficult to assign.
Fish produce sounds using various mechanisms, including:

Stridulation: Rubbing body parts together, such as fin spines against bony plates.

Swim Bladder Vibration: Using specialized muscles to rapidly contract and vibrate the swim bladder.

Grinding Teeth: Producing sounds by grinding their teeth.

Hydrodynamic Sounds: Creating water displacement sounds through movements like swimming and jaw snapping.

Expelling Air: Releasing air bubbles from the mouth or rear end.

Fish use their swim bladder and specialized muscles to produce sounds.
Fish can produce a variety of sounds, including:

Grunts

Croaks

Snaps

Pops

Drumming sounds

These sounds vary in frequency, duration, and intensity depending on the species and the context of the communication.
Yes. Fish don’t have outer ears, but they have structures inside their heads called otolith organs that work similarly to our inner ears. They don’t need outer ears because waterborne sound passes right through fleshy tissue to hit the very dense otoliths. They also use other internal structures to focus sound to these ear bones. Fish also have another structure called a lateral line that senses vibrations, including sound. So fish have two kinds of ears. Sound is really important to them.
Rarely, humans can hear some very loud fish sounds underwater, however, the human ear isn’t adapted for hearing underwater. We need hydrophones, which are microphones specially designed for underwater.
Fish use sounds to communicate a range of messages:

Mating calls: To attract mates or synchronize spawning.

Territorial signals: To establish and defend territories.

Alarm calls: To warn conspecifics of predators.
Yes, fish sounds are species-specific, allowing researchers to identify different species based on their acoustic signatures. It is just very difficult to tell which species is making which sound. But when we can, species-specific sound can be used with passive acoustic monitoring to study fish populations and behaviors without direct observation.
Fish sounds can be used in marine conservation by:

Monitoring fish populations: Tracking the presence and abundance of species in specific areas.

Identifying spawning and mating sites: Protecting critical habitats based on acoustic cues.

Assessing ecosystem health: Using changes in soundscapes to detect ecological shifts or impacts from human activities.
Yes, noise pollution from ships, industrial activities, and other human sources can interfere with fish communication. This can lead to disrupted mating calls, impaired predator detection, and increased stress levels, ultimately affecting fish behavior and survival.
Challenges in studying fish sounds include:

Technical limitations: Difficulty in capturing high-quality recordings in various aquatic environments.

Environmental noise: Background noise from natural and anthropogenic sources can mask fish sounds.

Behavioral variability: In nature, using standard video and audio to match sounds to images rarely works. Fish often show no distinct movements related to sound production, and there are usually many nearby, off-screen individuals.

1. When did people first start studying fish sounds?

The concept of bioacoustics dates back to Aristotle (Lynch 2022), who first noted that fish make sounds. However, it wasn't until World War II that scientists made significant advancements. During the war, submarines used sonar technology to detect enemy vessels. Sounds that seemed to be enemy ships or submarines frequently alarmed sonar technicians, however, they eventually realized that the ocean was full of natural sounds.

From 1948 to 1970, marine biologist Marie Fish and engineer William Mowbray worked with the U.S. Navy to distinguish biological sounds from submarines (Goldfarb 2021). They published articles and a foundational book on fish sounds, establishing the basis for fish bioacoustics. However, almost all of these recordings were obtained from captive fish undergoing various unnatural stimuli. While these told us that these species could make sounds, they did not necessarily document natural sounds. Few of the sounds they documented have actually been confirmed from nature.

FAQ- Fish Sounds

2. Do all fish species produce sounds?

Recent studies show that as many as 80% of all bony fish species likely use sounds to communicate (Looby 2023). That’s at least 20,000 species. If you drop a hydrophone (an underwater microphone) in almost any natural fish environment, you will hear myriad sounds in the 100 Hz - 2.5 kHz range that are likely to be fish sounds. However, if there are more than one species present, it is exceedingly difficult to tell which species made each sound. Fish don’t open their mouths to call and they rarely have conspicuous movements that show you which is making the sound. Fish sounds are not difficult to record, but they are difficult to assign.

3. How do fish produce sounds?

Fish produce sounds using various mechanisms, including:

Stridulation: Rubbing body parts together, such as fin spines against bony plates.
Swim Bladder Vibration: Using specialized muscles to rapidly contract and vibrate the swim bladder.
Grinding Teeth: Producing sounds by grinding their teeth.
Hydrodynamic Sounds: Creating water displacement sounds through movements like swimming and jaw snapping.
Expelling Air: Releasing air bubbles from the mouth or rear end.

Fish use their swim bladder and specialized muscles to produce sounds.

5. Do fish have ears?

Yes. Fish don’t have outer ears, but they have structures inside their heads called otolith organs that work similarly to our inner ears. They don’t need outer ears because waterborne sound passes right through fleshy tissue to hit the very dense otoliths. They also use other internal structures to focus sound to these ear bones. Fish also have another structure called a lateral line that senses vibrations, including sound. So fish have two kinds of ears. Sound is really important to them.

6. Can humans hear fish sounds underwater?

Rarely, humans can hear some very loud fish sounds underwater, however, the human ear isn’t adapted for hearing underwater. We need hydrophones, which are microphones specially designed for underwater.

7. What types of messages do fish communicate?

Fish use sounds to communicate a range of messages:

Mating calls: To attract mates or synchronize spawning.
Territorial signals: To establish and defend territories.
Alarm calls: To warn conspecifics of predators.

4. What types of sounds do fish make?

Fish can produce a variety of sounds, including:

Grunts
Croaks
Snaps
Pops
Drumming sounds

These sounds vary in frequency, duration, and intensity depending on the species and the context of the communication.

9. How can fish sounds be used in marine conservation?

Fish sounds can be used in marine conservation by:

Monitoring fish populations: Tracking the presence and abundance of species in specific areas.
Identifying spawning and mating sites: Protecting critical habitats based on acoustic cues.
Assessing ecosystem health: Using changes in soundscapes to detect ecological shifts or impacts from human activities.

8. Can fish sounds be used to identify different species?

Yes, fish sounds are species-specific, allowing researchers to identify different species based on their acoustic signatures. It is just very difficult to tell which species is making which sound. But when we can, species-specific sound can be used with passive acoustic monitoring to study fish populations and behaviors without direct observation.

11. What are the challenges in studying fish sounds?

Challenges in studying fish sounds include:

Technical limitations: Difficulty in capturing high-quality recordings in various aquatic environments.
Environmental noise: Background noise from natural and anthropogenic sources can mask fish sounds.
Behavioral variability: In nature, using standard video and audio to match sounds to images rarely works. Fish often show no distinct movements related to sound production, and there are usually many nearby, off-screen individuals.

10. Can fish sounds be affected by noise pollution?

Yes, noise pollution from ships, industrial activities, and other human sources can interfere with fish communication. This can lead to disrupted mating calls, impaired predator detection, and increased stress levels, ultimately affecting fish behavior and survival.

Marine conservation bioacoustics is the study of sound production and perception in marine organisms and their use of sound to understand and protect marine ecosystems. This field combines principles from marine biology, ecology, and acoustics to monitor marine life and assess the health of marine environments.
Scientists record fish sounds using underwater microphones called hydrophones. These devices are placed in marine habitats to capture the wide range of sounds produced by fish and other marine organisms. You can throw a hydrophone over the edge of a boat and listen and you can record these sessions on standard recorders. Or you can attach a long-term recorder to the hydrophone and leave it out for weeks or months. When you do this, it’s called passive acoustic monitoring (PAM). Self-contained PAM devices often look like short pipe sections with a hydrophone nub on one end.
Current bioacoustic monitoring methods face several challenges:

Lack of Identified sounds for different species: While perhaps 25,000 species of fish make sound, we only have recordings of a few hundred—few of which are recordings from nature.

Expense: capturing high-quality recordings in aquatic environments usually requires expensive equipment and often boats or divers for deployment.

Environmental noise: Background noise from natural and anthropogenic (human) sources can mask fish sounds. (Imagine what that does to the fish.)

Impossibility for us to hear: Our ears don’t work well underwater, which is why Jacques Cousteau described the oceans as a “silent world.”

Large number of “suspects”: On a coral reef, there can be hundreds of fish around a hydrophone. Discovering which one made the sound is exceedingly difficult.

Behavioral variability: Fish often show no distinct movements related to sound production, making it hard to match sounds to specific individuals or species, even when we have recordings of both audio and video.
Passive acoustic monitoring (PAM) is a technique used to record sounds in the environment. Passive acoustics means “listening” as opposed to active acoustics, which means using sonar (first making sounds and then listening for reflections.) For passive acoustics, hydrophones are deployed in marine habitats. When you record from these for very long periods, it is called passive acoustic monitoring. PAM allows scientists to monitor marine life and environmental conditions over extended periods, around the clock.
Studying underwater soundscapes is crucial because:

Ecosystem health: Soundscapes provide insights into the health and biodiversity of marine ecosystems.

Behavioral studies: It helps us understand how marine organisms use sound for communication, navigation, and mating.

Conservation efforts: It helps identify critical habitats and assess the impact of human activities on marine life.
Human activities such as shipping, industrial activities, and recreational boating introduce noise pollution into marine environments. This noise pollution can interfere with the communication, mating calls, and predator-prey interactions of marine organisms. It can also cause stress and behavioral changes, ultimately affecting their survival and reproduction.
Scientists have been using marine bioacoustics to study whales for decades, for example to follow migration and track populations. Using sound for other types of animals is a relatively new development. With new techniques and technologies, we can:

Monitor fish populations: Tracking the presence and abundance of species in specific areas.

Identify critical habitats: Protecting spawning and mating sites based on acoustic cues.

Assess ecosystem health: Using changes in soundscapes to detect ecological shifts or impacts from human activities.
Climate change affects underwater soundscapes by:

Altering habitats: Rising temperatures and ocean acidification can change the distribution and behavior of marine species, impacting the sounds they produce. For instance, coral reef soundscapes have been shown to vary with the health of the reef, which is influenced by temperature and acidity levels. Major bleaching events are killing coral reefs around the world (Oceanographic 2022).

Altering the propagation of sound: Changes in water temperature, salinity, and acidity affect how sound travels underwater. Warmer waters can enhance sound transmission, allowing sounds to travel further, which can increase noise levels and affect marine species' ability to communicate. This can lead to changes in how species like the North Atlantic right whale interact and locate each other (Phys.org., 2022).

Baseline data: It’s important to collect baseline acoustic data to understand and mitigate the effects of these changes on marine ecosystems. Long-term monitoring of underwater soundscapes can provide insights into ecological shifts and help track changes in marine biodiversity and habitat health (Freeman 2023).
Yes, bioacoustics can track fish populations by identifying species-specific sounds and monitoring their presence and activity over time. This non-invasive method provides valuable data on population dynamics, behavior, and habitat use without disturbing the animals. When we know which sounds come from which species, we can identify critical habitats and breeding grounds for protection. This is already being done with grouper in a few places in the Gulf of Mexico and Caribbean Sea (Mann et al., 2008; Wall et al., 2014).
Underwater sounds help evaluate ecosystem health by providing:

Biodiversity indicators: Diverse and active soundscapes typically indicate healthy ecosystems.

Disturbance detection: Changes or reductions in expected sounds can signal ecological disturbances or declines in certain species.

Recovery: Recent work shows that through restoration practices, coral reefs improve their soundscapes.
Bioacoustic data helps fisheries management by:

Species identification: Recognizing specific fish sounds allows for monitoring and managing fish populations effectively.

Habitat protection: Identifying important breeding and feeding areas to implement conservation measures.

Regulatory decisions: Providing data to inform policies and regulations aimed at sustainable fisheries management.

1. What is marine conservation bioacoustics?

Marine conservation bioacoustics is the study of sound production and perception in marine organisms and their use of sound to understand and protect marine ecosystems. This field combines principles from marine biology, ecology, and acoustics to monitor marine life and assess the health of marine environments.

2. How do scientists record fish sounds?

Scientists record fish sounds using underwater microphones called hydrophones. These devices are placed in marine habitats to capture the wide range of sounds produced by fish and other marine organisms. You can throw a hydrophone over the edge of a boat and listen and you can record these sessions on standard recorders. Or you can attach a long-term recorder to the hydrophone and leave it out for weeks or months. When you do this, it’s called passive acoustic monitoring (PAM). Self-contained PAM devices often look like short pipe sections with a hydrophone nub on one end.

FAQ – Marine Conservation Bioacoustics

3. What are some limitations of current bioacoustic methods for monitoring fish?

Current bioacoustic monitoring methods face several challenges:

Lack of Identified sounds for different species: While perhaps 25,000 species of fish make sound, we only have recordings of a few hundred—few of which are recordings from nature.
Expense: capturing high-quality recordings in aquatic environments usually requires expensive equipment and often boats or divers for deployment.
Environmental noise: Background noise from natural and anthropogenic (human) sources can mask fish sounds. (Imagine what that does to the fish.)
Impossibility for us to hear: Our ears don’t work well underwater, which is why Jacques Cousteau described the oceans as a “silent world.”
Large number of “suspects”: On a coral reef, there can be hundreds of fish around a hydrophone. Discovering which one made the sound is exceedingly difficult.
Behavioral variability: Fish often show no distinct movements related to sound production, making it hard to match sounds to specific individuals or species, even when we have recordings of both audio and video.

5. Why is it important to study underwater soundscapes?

Studying underwater soundscapes is crucial because:

Ecosystem health: Soundscapes provide insights into the health and biodiversity of marine ecosystems.
Behavioral studies: It helps us understand how marine organisms use sound for communication, navigation, and mating.
Conservation efforts: It helps identify critical habitats and assess the impact of human activities on marine life.

4. What is passive acoustic monitoring (PAM)?

Passive acoustic monitoring (PAM) is a technique used to record sounds in the environment. Passive acoustics means “listening” as opposed to active acoustics, which means using sonar (first making sounds and then listening for reflections.) For passive acoustics, hydrophones are deployed in marine habitats. When you record from these for very long periods, it is called passive acoustic monitoring. PAM allows scientists to monitor marine life and environmental conditions over extended periods, around the clock.

7. How is bioacoustic data used in marine conservation?

Scientists have been using marine bioacoustics to study whales for decades, for example to follow migration and track populations. Using sound for other types of animals is a relatively new development. With new techniques and technologies, we can:

Monitor fish populations: Tracking the presence and abundance of species in specific areas.
Identify critical habitats: Protecting spawning and mating sites based on acoustic cues.
Assess ecosystem health: Using changes in soundscapes to detect ecological shifts or impacts from human activities.

6. What is the impact of human activities on underwater soundscapes?

Human activities such as shipping, industrial activities, and recreational boating introduce noise pollution into marine environments. This noise pollution can interfere with the communication, mating calls, and predator-prey interactions of marine organisms. It can also cause stress and behavioral changes, ultimately affecting their survival and reproduction.

8. How does climate change impact underwater soundscapes?

Climate change affects underwater soundscapes by:

Altering habitats: Rising temperatures and ocean acidification can change the distribution and behavior of marine species, impacting the sounds they produce. For instance, coral reef soundscapes have been shown to vary with the health of the reef, which is influenced by temperature and acidity levels. Major bleaching events are killing coral reefs around the world (Oceanographic 2022).
Altering the propagation of sound: Changes in water temperature, salinity, and acidity affect how sound travels underwater. Warmer waters can enhance sound transmission, allowing sounds to travel further, which can increase noise levels and affect marine species' ability to communicate. This can lead to changes in how species like the North Atlantic right whale interact and locate each other (Phys.org., 2022).
Baseline data: It’s important to collect baseline acoustic data to understand and mitigate the effects of these changes on marine ecosystems. Long-term monitoring of underwater soundscapes can provide insights into ecological shifts and help track changes in marine biodiversity and habitat health (Freeman 2023).

10. How do underwater sounds help in evaluating ecosystem health?

Underwater sounds help evaluate ecosystem health by providing:

Biodiversity indicators: Diverse and active soundscapes typically indicate healthy ecosystems.
Disturbance detection: Changes or reductions in expected sounds can signal ecological disturbances or declines in certain species.
Recovery: Recent work shows that through restoration practices, coral reefs improve their soundscapes.

9. Can bioacoustics be used to track fish populations?

Yes, bioacoustics can track fish populations by identifying species-specific sounds and monitoring their presence and activity over time. This non-invasive method provides valuable data on population dynamics, behavior, and habitat use without disturbing the animals. When we know which sounds come from which species, we can identify critical habitats and breeding grounds for protection. This is already being done with grouper in a few places in the Gulf of Mexico and Caribbean Sea (Mann et al., 2008; Wall et al., 2014).

11. How does bioacoustic data help fisheries management?

Bioacoustic data helps fisheries management by:

Species identification: Recognizing specific fish sounds allows for monitoring and managing fish populations effectively.
Habitat protection: Identifying important breeding and feeding areas to implement conservation measures.
Regulatory decisions: Providing data to inform policies and regulations aimed at sustainable fisheries management.

References:

Climate change affects ocean soundscape. Oceanographic. (2022, April 20). https://oceanographicmagazine.com/news/climate-change-affects-ocean-soundscape/

Freeman, L. A., Duane, D., Rooney, I., & Freeman, S. E. (2023, May 7). Turning up ocean temperature & volume-Underwater soundscapes in a changing climate. Acoustical Society of America News. https://acoustics.org/turning-up-ocean-temperature-volume-underwater-soundscapes-in-a-changing-climate/

Goldfarb, B. (2021, April). Biologist Marie Fish Catalogued the Sounds of the Ocean for the World to Hear. Smithsonian Magazine. https://www.smithsonianmag.com/science-nature/biologist-marie-fish-catalogued-sounds-ocean-world-hear-180977152/

Looby, A., Erbe, C., Bravo, S., Cox, K., Davies, H. L., Di Iorio, L., Jézéquel, Y., Juanes, F., Martin, C. W., Mooney, T. A., Radford, C., Reynolds, L. K., Rice, A. N., Riera, A., Rountree, R., Spriel, B., Stanley, J., Vela, S., & Parsons, M. J. (2023). Global inventory of species categorized by known underwater sonifery. Nature Scientific Data, 10(1). https://doi.org/10.1038/s41597-023-02745-4

Lynch, C. (2022, May 2). Fish Are Chattier Than Previously Thought. The Scientist. https://www.the-scientist.com/fish-are-chattier-than-previously-thought-69938

Mann, D. A., Locascio, J. V., Coleman, F. C., & Koenig, C. C. (2008). Goliath grouper Epinephelus itajara sound production and movement patterns on aggregation sites. Endangered Species Research 7:229-236.

Phys.org. (2022, March 24). Warming oceans will significantly alter how sound travels underwater. Phys.org. https://phys.org/news/2022-03-oceans-significantly-underwater.html#google_vignette

Wall, C. C., Simard, P., Lindemuth, M., Lembke, C., Naar, D. F., Hu, C., Barnes, B. B., Muller-Karger, F. E., & Mann, D. A. (2014). Temporal and spatial mapping of red grouper Epinephelus morio sound production. Journal of Fish Biology 85:1470-1488.