MELVILLE, N.Y., Nov. 21, 2024 – In the winter of 2022-2023, nearly a dozen whales died off the coast of New Jersey, near the sites of several proposed wind farms. Their deaths prompted concern that related survey work being conducted in the area somehow contributed to their deaths.
Michael Stocker of Ocean Conservation Research will present his work Thursday, Nov. 21, at 3:29 p.m. ET in a session dedicated to examining the circumstances surrounding these whale deaths, as part of the virtual 187th Meeting of the Acoustical Society of America, running Nov. 18-22, 2024.
Researchers retrieve an instrument package from the Cook Inlet. Could noise from these surveys like these have led to the death of almost a dozen whales during winter of 2022-2023? Credit: Michael Stocker
In pursuit of clean energy goals and to reduce atmospheric carbon emissions, developers are increasingly exploring building wind turbines in the waters off the East Coast of the United States. Three offshore wind farms are already in operation, with several more planned or underway. These wind farms stand to generate a significant amount of carbon-free electricity, which can help coastal states meet their decarbonization goals.
The increased presence of these turbines in coastal waters, along with the noise from construction and surveys, has led to concerns of their impact on marine life. In particular, cetaceans such as whales and dolphins are likely to be sensitive to the noises and increased marine traffic brought by these turbines.
However, the Marine Mammal Commission, a federal oversight agency, states there is no evidence linking the whales that died in the New Jersey region in the winter of 2022-2023 to wind energy development.
According to necropsies performed on recovered whales, many of them died from collisions with ships. The Marine Mammal Commission notes that this is not a particularly unusual occurrence, nor is the number of whale deaths in this period higher than average. A rise in ship strikes over the last decade is mostly due to a simple combination of more whales plus more ships.
“In the case of a lot of whales, population recoveries since the cessation of commercial whaling are coincident with increasing shipping traffic and increasing fishing efforts,” said Stocker. “This is resulting in increased interactions between whales and the industrialization of the ocean.”
Stocker, however, is concerned that the increased presence of survey ships in and around New Jersey waters may have exacerbated this issue.
“Were the ship strikes just a coincidence?” asked Stocker. “Or were they a product of compromised whale vigilance due to aggregated stress factors?”
Survey ships are employed by wind farm developers to map the seafloor in preparation for construction. These ships use underwater acoustic devices in their efforts, which can stress marine mammals such as whales. While one survey ship likely has little effect, Stocker highlights that 11 different surveys were operating in the region from December 2022 to March 2023, and that the cumulative impact of these surveys has not been properly evaluated.
Stocker hopes his Thursday session will spark a discussion among attendees with the goal of identifying approaches to minimize whale deaths in the future.
ASA PRESS ROOM In the coming weeks, ASA’s Press Room will be updated with newsworthy stories and the press conference schedule at https://acoustics.org/asa-press-room/.
LAY LANGUAGE PAPERS ASA will also share dozens of lay language papers about topics covered at the conference. Lay language papers are summaries (300-500 words) of presentations written by scientists for a general audience. They will be accompanied by photos, audio, and video. Learn more at https://acoustics.org/lay-language-papers/.
PRESS REGISTRATION ASA will grant free registration to credentialed and professional freelance journalists. If you are a reporter and would like to attend the virtual meeting and/or press conferences, contact AIP Media Services at media@aip.org. For urgent requests, AIP staff can also help with setting up interviews and obtaining images, sound clips, or background information.
ABOUT THE ACOUSTICAL SOCIETY OF AMERICA The Acoustical Society of America is the premier international scientific society in acoustics devoted to the science and technology of sound. Its 7,000 members worldwide represent a broad spectrum of the study of acoustics. ASA publications include The Journal of the Acoustical Society of America (the world’s leading journal on acoustics), JASA Express Letters, Proceedings of Meetings on Acoustics, Acoustics Today magazine, books, and standards on acoustics. The society also holds two major scientific meetings each year. See https://acousticalsociety.org/.
–The research described in this Acoustics Lay Language Paper may not have yet been peer reviewed–
Impact of sound on aquatic animals
Human-generated sound, called ‘anthropogenic sound,’ is now widely recognized as an environmental stressor. It affects aquatic life in both marine and freshwater habitats. Over the last few decades, policy makers, animal welfare communities, behavioural biologists and environmental managers have been increasingly interested in understanding how man-made sound may lead to negative consequences on both terrestrial and underwater animals. Aquatic animals can be negatively affected by anthropogenic sound in many ways. For example anthropogenic sound can mask biologically relevant sounds, cause attentional shifts, affect foraging performance and interfere in communications in aquatic animals among taxa. Therefore, we need to understand how anthropogenic sound may affect individuals, to eventually be able to assess the impact of anthropogenic sound on populations, communities, and ecosystems.
Many crustaceans and fish species have been artificially introduced to confined areas for different purposes. Crustaceans and fish are being used in laboratory conditions for scientific research, in aquaria and zoos for entertainment, as well as in aquaculture facilities (e.g., cages, races, pens) for breeding, restocking and harvesting around the world. As a result, aquatic animals in captivity may be continuously exposed to a variety of sound sources. Although there are relatively well-documented studies exploring anthropogenic sound effects on aquatic animals across taxa in the Global North Countries, this field of research is less developed in the Global South Countries. Moreover, policy makers have already set regulations for marine environments to safeguard a so-called good environmental status, but there are no agreements yet for freshwater habitats. This means freshwater crustaceans and fishes in a diversity of waterbody types are more or less exposed to man-made sound without any incentive to control impact and without any protection by law.
Sound exposure studies
To better understand how sound affects aquatic animals, I conducted several sound exposure studies on captive fish and crustaceans. In my experimental studies, I explored how anthropogenic sound affects captive fish (e.g., zebrafish and guppy) and crustaceans (red cherry shrimp). Figure 1 illustrates behavioral changes in red cherry shrimp when exposed to different sound levels, showing how they react to sound stress.
I examined various sound exposure treatments to provide insights that may be useful for future explorations for indoor and outdoor sound impact studies as well as for assessing animal welfare and productivity in captive situations. For example, I explored short-term behavioural parameters, which are indicators of sound-related stress, disturbance and deterrence. My findings may also raise awareness for sound levels in laboratories and the potential effect on reliability for fish as a model species for medical and pharmaceutical studies. As a follow-up step of my PhD research, I also explored the complexity of sound fields in indoor fish tanks by selecting a different set-up for each study, which makes behavioural analyses and direct comparisons not only relevant within each study, but also provides insight into the role of fish tank acoustics on ‘natural’ and experimental exposure conditions. Several behavioural states are likely to reflect considerable changes in underlying physiology, which would be interesting and feasible to investigate for more long-term consequences, but this was beyond the scope of the current step of my research lab priorities.
Development of bioacoustics in Iran and future directions
This research study is a pioneering effort in a relatively new field in Iran. This research is important because Iran has a broad range of coastlines with The Caspian Sea, The Persian Gulf and Oman Sea and there are quite diverse habitats and fragile ecosystems in these aquatic areas (See figure 2). However, yet there are large gaps in our knowledge of effects of anthropogenic sound on aquatic animals in Iran. Further studies are needed to assess anthropogenic sound impacts on aquatic animals and the potential cascading effects at the community level of the aquatic environment in Iran. This research, a series of experiments, lays the groundwork for future bioacoustics studies in Iran and other countries in the West Asia. I call, therefore, for more grounded laboratory-based and field based empirical research of global collaborations and high quality data collection towards open science in bioacoustics.
Figure 2. An overview of the geographical location of Iran’s aquatic habitats (yellow circles); The Caspian Sea in the north of Iran and The Persian Gulf and The Gulf of Oman/Oman Sea. Image courtesy of: https://www.google.com/maps
Acknowledgments
Finally, I am very grateful to my graduate M.Sc. students: Reza Mohsenpour, Sasan Azarm-Karnagh, Marziyeh Amini Fard for their excellent collaborations in behavioural studies and high quality data collection at the Fisheries Department, Faculty of Natural Resources, University of Guilan, Sowmeh Sara, Iran. I established and set up my research lab in 2016 and actively recruit enthusiastic undergraduate and graduate students by organizing workshops, seminars, mini research projects and relevant course material to develop this field of academic research in Iran. Hereby I would like to thank Hans Slabbekoorn my PhD supervisor at Leiden University who have helped and supported me to develop my underwater bioacoustics lab in my home country, Iran.
Selected references:
Azarm-Karnagh, S., López Greco, L., & Shafiei Sabet, S. (2024). Anthropogenic noise impacts on invertebrates: case of freshwater red cherry shrimp (Neocaridina davidi). In The Effects of Noise on Aquatic Life: Principles and Practical Considerations (pp. 1-12). Cham: Springer International Publishing.
Azarm-Karnagh, S., López Greco, L., & Shafiei Sabet, S. (2023). Annoying noise: effect of anthropogenic underwater noise on the movement and feeding performance in the red cherry shrimp, Neocaridina davidi. Frontiers in Ecology and Evolution, 11, 1091314.
Shafiei Sabet, S., Karnagh, S. A., & Azbari, F. Z. (2019). Experimental test of sound and light exposure on water flea swimming behaviour. In Proceedings of Meetings on Acoustics (Vol. 37, No. 1). AIP Publishing.
Radford, A. N., Kerridge, E., & Simpson, S. D. (2014). Acoustic communication in a noisy world: can fish compete with anthropogenic noise?. Behavioral Ecology, 25(5), 1022-1030.
Slabbekoorn, H., Bouton, N., van Opzeeland, I., Coers, A., ten Cate, C., & Popper, A. N. (2010). A noisy spring: the impact of globally rising underwater sound levels on fish. Trends in ecology & evolution, 25(7), 419-427.
Popper, A. N., & Hastings, M. C. (2009). The effects of anthropogenic sources of sound on fishes. Journal of fish biology, 75(3), 455-489.
OTTAWA, Ontario, May 15, 2024 – An emperor penguin’s sex determines the nature of their courtship call – male vocalizations are composed of long, slow bursts with lower frequency tones than the female version. But calls of SeaWorld San Diego male penguin E-79 caught the attention of researchers by defying this binary. Also unusual was this penguin’s male companion, E-81. The pair “kept company” and sometimes exhibited ritual courtship displays.
Researchers from Applied Ocean Sciences, the Marine Technology Society, Hubbs SeaWorld Research Institute, and SeaWorld San Diego investigated the courtship calls of E-79 and E-81. Kerri Seger will present their work Wednesday, May 15, at 10:15 a.m. EDT Time as part of a joint meeting of the Acoustical Society of America and the Canadian Acoustical Association, running May 13-17 at the Shaw Centre located in downtown Ottawa, Ontario, Canada.
Emperor E-79 shown at the end of a display sequence after calling. When the birds call, their bills are facing generally downward and only slightly opened. The sound is radiated downward from the bill and to a lesser extent outward from the breast. Image credit: Linda M. Henry, SeaWorld San Diego.
The emperor penguin courtship display includes strutting, bowing, emitting the distinctive call, and swinging the head. This courtship display is also exhibited in other social contexts, especially around chicks and juvenile penguins.
“The sound isn’t melodious by comparison with songbird calls – it has been likened to a malfunctioning starter motor,” said bioacoustician Ann Bowles. “Our interest was in the timing of the calls, which are composed of a series of noisy bursts. A lot of individual information is encoded in the timing of these bursts.”
Unexpected vocalizations like E-79’s could indicate a developmental or health issue or genetic anomaly. However, the team couldn’t address questions about the bird’s condition without taking a very basic step – they had to quantify the range of variability in “normal” calls of other emperor penguins and compare them to E-79’s calls in detail. Not only did they need to record the birds in their below-freezing enclosure, but they also had to refine the usual technique for analyzing the bursts.
“We found that if we looked at the bursts overall, they were structured mainly like the male-type calls, but they contained little initial amplitude peaks in front of many bursts and a series of very short peaks in one of the long central bursts that would not have been typical of adults of either sex,” Seger said.
The team hypothesizes that the feminine or juvenile qualities of E-79’s bursts could partially explain E-81’s interest.
Refining the technique to study penguin calls has important applications beyond E-79.
“Seabird calls haven’t received anything like the attention that songbirds get, partly because they’re difficult to analyze,” said Seger. “We’re hoping new approaches like the one we’re working on will help. These calls can be indicators of developmental differences, health, reproductive state, or genetic makeup. Emperors are now considered to be at risk because of changing ice conditions in the Antarctic. Tools for assessing their condition or reproductive state remotely could be very helpful for assessing large numbers safely.”
ASA PRESS ROOM In the coming weeks, ASA’s Press Room will be updated with newsworthy stories and the press conference schedule at https://acoustics.org/asa-press-room/.
LAY LANGUAGE PAPERS ASA will also share dozens of lay language papers about topics covered at the conference. Lay language papers are summaries (300-500 words) of presentations written by scientists for a general audience. They will be accompanied by photos, audio, and video. Learn more at https://acoustics.org/lay-language-papers/.
PRESS REGISTRATION ASA will grant free registration to credentialed and professional freelance journalists. If you are a reporter and would like to attend the in-person meeting or virtual press conferences, contact AIP Media Services at media@aip.org. For urgent requests, AIP staff can also help with setting up interviews and obtaining images, sound clips, or background information.
ABOUT THE ACOUSTICAL SOCIETY OF AMERICA The Acoustical Society of America is the premier international scientific society in acoustics devoted to the science and technology of sound. Its 7,000 members worldwide represent a broad spectrum of the study of acoustics. ASA publications include The Journal of the Acoustical Society of America (the world’s leading journal on acoustics), JASA Express Letters, Proceedings of Meetings on Acoustics, Acoustics Today magazine, books, and standards on acoustics. The society also holds two major scientific meetings each year. See https://acousticalsociety.org/.
ABOUT THE CANADIAN ACOUSTICAL ASSOCIATION/ASSOCIATION CANADIENNE D’ACOUSTIQUE
fosters communication among people working in all areas of acoustics in Canada
promotes the growth and practical application of knowledge in acoustics
encourages education, research, protection of the environment, and employment in acoustics
is an umbrella organization through which general issues in education, employment and research can be addressed at a national and multidisciplinary level
The CAA is a member society of the International Institute of Noise Control Engineering (I-INCE) and the International Commission for Acoustics (ICA), and is an affiliate society of the International Institute of Acoustics and Vibration (IIAV). Visit https://caa-aca.ca/.
Rolf Müller – rolf.mueller@vt.edu
X (twitter): @UBDVTLab
Instagram: @ubdvtcenter
Department of Mechanical Engineering, Virginia Tech, Blacksburg, Virginia, 24061, United States
Popular version of 4aAB7 – Of bats and robots
Presented at the 186th ASA Meeting
Read the abstract at https://doi.org/10.1121/10.0027373
–The research described in this Acoustics Lay Language Paper may not have yet been peer reviewed–
Given the ongoing revolution in AI, it may appear that all humanity can do now is wait for AI-powered robots to take over the world. However, while stringing together eloquently worded sentences is certainly impressive, AI is still far from dealing with many of the complexities of the real world. Besides serving the sinister goal of world-domination, robots that have the intelligence to accomplish demanding missions in complex environments could transform humanity’s ability to deal with fundamental key challenges to its survival, e.g., production of food and regrowable materials as well as maintaining healthy ecosystems.
To accomplish the goal of having a robot operate autonomously in complex real-world environments, a variety of methods have been developed – typically with mixed results at best. At the basis of these methods are usually two related concepts: The creation of a model for the geometry of an environment and the use of deterministic templates to identify objects. However, both approaches have already proven to be limited in their applicability, reliability, as well as due to their often prohibitively high computational cost.
Bats navigating dense vegetation – such as in rainforests of Southeast Asia, where our fieldwork is being carried out – may provide a promising alternative to the current approaches: The animals sense their environments through a small number of brief echoes to ultrasonic pulses. The comparatively large wavelengths of these pulses (millimeter to centimeter) combined with the fact that the ears of the bats fall not too far above from these wavelengths on the size scale condemns bat biosonar to poor angular resolution. This prevents the animals from resolving densely packed scatterers such as leave in a foliage. Hence, the echoes that bats navigating under such conditions have to deal with inputs that can be classified as “clutter”, i.e., signals that consists of contributions from many unresolvable scatterers that must be treated as random due to lack of knowledge. The nature of the clutter echoes makes it unlikely that bats having to deal with complex environments rely heavily on three-dimensional models of their surroundings and deterministic templates.
Hence, bats must have evolved sensing paradigms to ensure that the clutter echoes contain the relevant sensory information and that this information can be extracted. Coupling between sensing and actuation could very well play a critical role in this. Hence, robotics might be of pivotal importance in replicating the skills of bats in sensing and navigating their environments. Similarly, the deep-learning revolution could bring a previously unavailable ability to extract complex patterns from data to bear on the problem of extracting insight from clutter echoes. Taken together, insights from these approaches could lead to novel acoustics-based paradigms for obtaining relevant sensory information on complex environment in a direct and highly parsimonious manner. These approaches could then enable autonomous robots that can learn to navigate new environments in a fast and highly efficient manner and transform the use of autonomous systems in outdoor tasks.
Biomimetic robots designed to reproduce the (a) biosonar sensing and (b) flapping-flight capabilities of bats. Design renderings by Zhengsheng Lu (a) and Adam Carmody (b).
As pilot demonstration for this approach, we present a twin pair of bioinspired robots, one to mimic the biosonar sensing abilities of bats and the other to mimic the flapping flight of the animals. The biosonar robot has been used successfully to identify locations and find passageways in complex, natural environments. To accomplish this, the biomimetic sonar has been integrated with deep-learning analysis of clutter echoes. The flapping-flight line of biomimetic robots has just started to reproduce some of the many degrees of freedom in the wing kinematics of bats. Ultimately, the two robots are to be integrated into a single system to investigate the coupling of biosonar sensing and flight.
Biologist, National Park Service, Natural Sounds and Night Skies Division
1201 Oakridge Drive Suite 100
Fort Collins, CO, 80524, United States
Popular version of 2aAB5 – From sounds to science on public lands: using emerging tools in terrestrial bioacoustics to understand national park soundscapes
Presented at the 186th ASA Meeting
Read the abstract at https://doi.org/10.1121/10.0026931
–The research described in this Acoustics Lay Language Paper may not have yet been peer reviewed–
In recent decades, audio recordings have helped scientists learn more about wildlife. Natural sounds help answer questions such as: which animals are present or absent from the environment? When do frogs and birds start calling in the spring? How are wildlife reacting to something humans are doing on a landscape?
As audio recordings have become less expensive and easier to collect, scientists can rapidly amass thousands of hours of data. To absorb this volume of data, instead of listening ourselves, we create automated detectors to find animal sounds in the recordings. However, it is a daunting and time-consuming task to create detectors for a diversity of species, habitats, and types of research.
Figure 1. Varied Thrush at Glacier Bay National Park and Preserve in 2015. Image courtesy of the National Park Service.
Several bird species vocalize at an acoustic monitoring station at Glacier Bay National Park and Preserve, including Pacific Wren, American Robin, and Varied Thrush. This example was recorded on June 13, 2017, at 3:22am local time. Audio recording courtesy of the National Park Service.
As more parks collect audio data to answer pressing research and management questions, building a unique automated detector for a single park project is no longer tenable. Instead, we are adopting emerging technology like BirdNET, a machine learning model trained on thousands of species worldwide (not just birds!). BirdNET provides us with more capacity. Instead of painstakingly building one detector for one project, BirdNET enables us to answer questions across multiple national parks.
But emerging technology poses more questions, too. How do we access these tools? What are the best practices for analyzing and interpreting outputs? How do we adapt new methods to answer many diverse park questions? We don’t all have the answers yet, but now we have code and workflows that help us process terabytes of audio, wrangle millions of rows of output, and produce plots to visualize and explore the data.
We are learning even more by collaborating with other scientists and land managers. So far, we’re exploring avian soundscapes at Glacier Bay National Park and Preserve across a decade of monitoring – from when birds are most vocally active during the spring (Fig.2), to when they are most active during the dawn chorus (Fig. 3). We are learning more about wildlife in the Chihuahuan Desert, wood frogs in Alaska, and how birds respond to simulated beaver structures at Rocky Mountain National Park.
The information we provide and interpret from audio data helps parks understand more about wildlife and actions to protect park resources. Translating huge piles of raw audio data into research insights is still a challenging task, but emerging tools are making it easier.
Figure 2. Heat map of BirdNET detection volume for selected focal species at Glacier Bay National Park and Preserve. (a) Hermit Thrush, (b) Pacific-slope Flycatcher, (c) Pacific Wren, (d) Ruby-crowned Kinglet, (e) Townsend’s Warbler, and (f) Varied Thrush. Dates ranging in color from purple to yellow indicate increasing numbers of detections. Dates colored gray had zero detections. White areas show dates where no recordings were collected. Image courtesy of the National Park Service.
Figure 3. Heat map of Varied Thrush detections across date and time of day at Glacier Bay National Park and Preserve. Timesteps ranging in color from purple to yellow indicate increasing numbers of detections. Timesteps colored gray had zero detections. White areas show times when no recordings were collected. Audio recordings were scheduled based on sunrise times. Image courtesy of the National Park Service.
Centre for Marine Science and Technology, Curtin University, Bentley, Western Australia, 6102, Australia
Benjamin Saunders
School of Molecular and Life Sciences
Curtin University
Bentley, Western Australia, Australia
Christine Erbe, Iain Parnum, Chong Wei, and Robert McCauley
Centre for Marine Science and Technology
Curtin University
Bentley, Western Australia, Australia
Popular version of 5aAB6 – The search to identify the fish species chorusing along the southern Australian continental shelf
Presented at the 185 ASA Meeting
Read the abstract at https://doi.org/10.1121/10.0023649
Please keep in mind that the research described in this Lay Language Paper may not have yet been peer reviewed.
Unknown fish species are singing in large aggregations along almost the entire southern Australian continental shelf on a daily basis, yet we still have little idea of what species these fish are or what this means to them. These singing aggregations are known as fish choruses, they occur when many individuals call continuously for a prolonged period, producing a cacophony of sound that can be detected kilometres away. It is difficult to identify fish species that chorus in offshore marine environments. The current scientific understanding of the sound-producing abilities of all fish species is limited and offshore marine environments are challenging to access. This project aimed to undertake a pilot study which attempted to identify the source species of three fish chorus types (shown below) detected along the southern Australian continental shelf off Bremer Bay in Western Australia from previously collected acoustic recordings.
Each fish chorus type occurred over the hours of sunset, dominating the soundscape within unique frequency bands. Have a listen to the audio file below to get a feeling for how noisy the waters off Bremer Bay become as the sun goes down and the fish start singing. The activity of each fish chorus type changed over time, indicating seasonality in presence and intensity. Chorus I and II demonstrated a peak in calling presence and intensity over late winter to early summer, while Chorus III demonstrated peak calling over late winter to late spring. This informed the sampling methodology of the pilot study, and in December 2019, underwater acoustic recorders and unbaited video recorders were deployed simultaneously on the seafloor along the continental shelf off Bremer Bay to attempt to collect evidence of any large aggregations of fish species present during the production of the fish choruses. Chorus I and the start of Chorus II were detected on the acoustic recordings, corresponding with video recordings of large aggregations of Red Snapper (Centroberyx gerrardi) and Deep Sea Perch (Nemadactylus macropterus). A spectrogram of the acoustic recordings and snapshots from the corresponding underwater video recordings are shown below.
The presence of large aggregations of Red Snapper present while Chorus I was also present was of particular interest to the authors. Previous dissections of this species had revealed that Red Snapper possessed anatomical features that could support sound production through the vibration of their swimbladder using specialised muscles. To explore this further, computerized tomography (CT) scans of several Red Snapper specimens were undertaken. We are currently undertaking 3D modelling of the sound-producing mechanisms of this species to compute the resonance frequency of the fish to better understand if this species could be producing Chorus I.
Listening to fish choruses can tell us about where these fish live, what habitats they use, their spawning behaviour, their feeding behaviour, can indicate their biodiversity, and in certain circumstances, can determine the local abundance of a fish population. For this information to be applied to marine spatial planning and fish species management, it is necessary to identify which fish species are producing these choruses. This pilot study was the first step in an attempt to develop an effective methodology that could be used to address the challenging task of identifying the source species of fish choruses present in offshore environments. We recommend that future studies take an integrated approach to species identification, including the use of arrays of hydrophones paired with underwater video recorders.
Figure 1. Behavioral changes of the freshwater red cherry shrimp in response to an underwater speaker. Behavioral responsiveness of shrimp when exposed to acoustic stimuli was categorized as movement activity impacts and feeding activity impacts (Image courtesy of: Azarm-Karnagh et al., 2023; © 2024 Springer Nature).
Figure 2. An overview of the geographical location of Iran’s aquatic habitats (yellow circles); The Caspian Sea in the north of Iran and The Persian Gulf and The Gulf of Oman/Oman Sea. Image courtesy of: 
Biomimetic robots designed to reproduce the (a) biosonar sensing and (b) flapping-flight capabilities of bats. Design renderings by Zhengsheng Lu (a) and Adam Carmody (b).
Each fish chorus type occurred over the hours of sunset, dominating the soundscape within unique frequency bands. Have a listen to the audio file below to get a feeling for how noisy the waters off Bremer Bay become as the sun goes down and the fish start singing. The activity of each fish chorus type changed over time, indicating seasonality in presence and intensity. Chorus I and II demonstrated a peak in calling presence and intensity over late winter to early summer, while Chorus III demonstrated peak calling over late winter to late spring. This informed the sampling methodology of the pilot study, and in December 2019, underwater acoustic recorders and unbaited video recorders were deployed simultaneously on the seafloor along the continental shelf off Bremer Bay to attempt to collect evidence of any large aggregations of fish species present during the production of the fish choruses. Chorus I and the start of Chorus II were detected on the acoustic recordings, corresponding with video recordings of large aggregations of Red Snapper (Centroberyx gerrardi) and Deep Sea Perch (Nemadactylus macropterus). A spectrogram of the acoustic recordings and snapshots from the corresponding underwater video recordings are shown below.
