Eden Zang - Academia.edu (original) (raw)

Papers by Eden Zang

Frontiers in marine science, Mar 6, 2024

Marine Mammal Science, Nov 1, 2023

Springer eBooks, Dec 31, 2022

Research Square (Research Square), Oct 29, 2023

Protected areas are typically managed as a network of sites exposed to varying anthropogenic cond... more Protected areas are typically managed as a network of sites exposed to varying anthropogenic conditions. Managing these networks bene ts from monitoring of conditions across sites to help prioritize coordinated efforts. Monitoring marine vessel activity and related underwater noise impacts across a network of protected areas, like the U.S. National Marine Sanctuary system, helps managers ensure the quality of habitats used by a wide range of marine species. Here, we use underwater acoustic detection of vessels to quantify vessel noise at 25 locations within eight marine sanctuaries including the Hawaiian Archipelago and the U.S. east and west coasts. Vessel noise metrics were paired with Automatic Identi cation System (AIS) vessel tracking data to derive a suite of robust vessel noise indicators for use across the network of marine protected areas. Network-wide comparisons revealed a spectrum of vessel noise conditions that closely matched AIS vessel tra c composition. Shifts in vessel noise were correlated with the decrease in vessel activity in early COVID-19 pandemic and vessel speed reduction initiatives. Improving our understanding of vessel noise conditions in these protected areas can help direct opportunities for reducing vessel noise, such as establishing and maintaining noise-free periods, enhancing port e ciency, engaging with regional and international vessel quieting initiatives, and leveraging co-bene ts of management actions for reducing ocean noise.

Male humpback whales (Megaptera novaeangliae) engage in complex singing displays during the winte... more Male humpback whales (Megaptera novaeangliae) engage in complex singing displays during the winter breeding season. This hierarchically structured song is composed of individual units arranged into phrases and themes that are produced for usually 12-18 minutes at a time and often repeated for multiple hours. Singing is presumed to be important for breeding, although its exact function remains a topic of debate. The effect of rising levels of anthropogenic noise in the ocean on humpback whale singing is still poorly understood. Here we report an incident where a singer instrumented with an acoustic tag was opportunistically exposed within a few hundred meters to noise from a transiting tugboat towing a barge between islands in Hawaii. The singing whale was recorded on the tag for several song cycles before, during and after exposure to the noise event. The recordings reveal that the whale persisted in singing normally at the beginning of the exposure, notably changed the unit and phrase structure while the vessels approached, and abruptly interrupted its singing when the vessels were closest. The whale returned to normal singing once the vessel noise abated. These results shed additional light on how humpback whales respond to anthropogenic noise.

Journal of the Acoustical Society of America, Oct 1, 2016

Coral reef soundscapes are increasingly becoming recognized as critical factors in the study of r... more Coral reef soundscapes are increasingly becoming recognized as critical factors in the study of reef dynamics, from the role they play in larval recruitment to the assessment of coral reef biodiversity and ecosystem stability. Snapping shrimp produce the predominant source of sound on most coral reefs at frequencies between 2 and 20 kHz. Their activity is influenced by a variety of abiotic factors. As such, coral reef soundscapes are prone to considerable flux and variation. However, this variation is still poorly understood on a variety of spatial and temporal scales, making it difficult to draw meaningful comparisons between the soundscapes of different reefs. We report on an effort to quantify the acoustic activity of snapping shrimp across 12 coral reef sites in the Pacific Ocean separated by distances ranging from hundreds of meters to thousands of kilometers, including reefs across the Hawaiian archipelago, the Northern Mariana Islands, and American Samoa. We use data obtained from long-term, bottom-moored acoustic recorders to document the variability in snapping shrimp activity observed on multiple temporal scales and examine factors correlated with this variability at each location.

Royal Society Open Science, Dec 1, 2017

To investigate the potential impacts of naval mine neutralization exercises (MINEX) on odontocete... more To investigate the potential impacts of naval mine neutralization exercises (MINEX) on odontocete cetaceans, a long-term passive acoustic monitoring study was conducted at a US Navy training range near Virginia Beach, USA. Bottommoored acoustic recorders were deployed in 2012-2016 near the epicentre of MINEX training activity and were refurbished every 2-4 months. Recordings were analysed for the daily presence/absence of dolphins, and dolphin acoustic activity was quantified in detail for the hours and days before and after 31 MINEX training events. Dolphins occurred in the area year-round, but there was clear seasonal variability, with lower presence during winter months. Dolphins exhibited a behavioural response to underwater detonations. Dolphin acoustic activity near the training location was lower during the hours and days following detonations, suggesting that animals left the area and/or reduced their signalling. Concurrent acoustic monitoring farther away from the training area suggested that the radius of response was between 3 and 6 km. A generalized additive model indicated that the predictors that explained the greatest amount of deviance in the data were the day relative to the training event, the hour of the day and circumstances specific to each training event.

Frontiers in remote sensing, Dec 12, 2022

between one and three consecutive days, while three sites had 5 days or more of consecutive prese... more between one and three consecutive days, while three sites had 5 days or more of consecutive presence, and one site had no consecutive delphinid presence, showing clear variation in how long they occupied different NMS. Marine mammals utilized all NMS and showed a wide range of occupancy, emphasizing the importance of understanding species use across different NMS as biological areas for migration, breeding and foraging.

The Office of National Marine Sanctuaries, part of the National Oceanic and Atmospheric Administr... more The Office of National Marine Sanctuaries, part of the National Oceanic and Atmospheric Administration, serves as the trustee for a system of underwater parks encompassing more than 620,000 square miles of ocean and Great Lakes waters. The 15 national marine sanctuaries and two marine national monuments within the National Marine Sanctuary System represent areas of America's ocean and Great Lakes environment that are of special national significance. Within their waters, giant humpback whales breed and calve their young, coral colonies flourish, and shipwrecks tell stories of our nation's maritime history. Habitats include beautiful coral reefs, lush kelp forests, whale migration corridors, spectacular deep-sea canyons, and underwater archaeological sites. These special places also provide homes to thousands of unique or endangered species and are important to America's cultural heritage. Sites range in size from less than one square mile to almost 583,000 square miles. They serve as natural classrooms and cherished recreational spots, and are home to valuable commercial industries. Because of considerable differences in settings, resources, and threats, each national marine sanctuary has a tailored management plan. Conservation, education, research, monitoring, and enforcement programs vary accordingly. The integration of these programs is fundamental to marine protected area management. The National Marine Sanctuaries Conservation Series reflects and supports this integration by providing a forum for publication and discussion of the complex issues currently facing the National Marine Sanctuary System. Topics of published reports vary substantially and may include descriptions of educational programs, discussions on resource management issues, and results of scientific research and monitoring projects. The series facilitates integration of natural sciences, socioeconomic and cultural sciences, education, and policy development to accomplish the diverse needs of NOAA's resource protection mandate. All publications are available on the Office of National Marine Sanctuaries website (sanctuaries.noaa.gov). Disclaimer The scientific results and conclusions, as well as any views or opinions expressed herein, are those of the authors and do not necessarily reflect the views of NOAA or the Department of Commerce. The mention of trade names or commercial products does not constitute endorsement or recommendation for use.

Proceedings of Meetings on Acoustics, 2019

Approximately half of the north Pacific humpback whale (Megaptera novaeangliae) population migrat... more Approximately half of the north Pacific humpback whale (Megaptera novaeangliae) population migrates from high latitude feeding grounds to Hawaii each winter and spring to breed. Beginning in 2015, unusually low numbers of whales began to be reported in Hawaii and this trend continued through 2018. To examine this reported trend, data from bottom-moored acoustic recorders were analyzed for the period between 2014 and 2018 at three monitoring sites off Maui. Male humpback whale song chorusing was used as a proxy for relative whale presence and activity within and between years. Results show that averaged monthly rootmean-square sound pressure levels trended down more than 6 dB re 1 uPa over the monitoring period, suggesting that the number of singing males or the amount of time they spent singing decreased substantially over the four-year period. Further, the timing of the chorusing peak within the seasons shifted, suggesting that whales left the breeding area earlier than in past years. It remains unclear whether these observations reflect a decrease in population size or a behavioral response to an environmental stressor. However, the trend is consistent with a concurrent decline reported by other researchers in Hawaii linked with climatic anomalies in the eastern north Pacific.

Endangered Species Research, Dec 17, 2020

Approximately half of the North Pacific humpback whale Megaptera novaeangliae stock visits the sh... more Approximately half of the North Pacific humpback whale Megaptera novaeangliae stock visits the shallow waters of the main Hawaiian Islands seasonally. Within this breeding area, mature males produce an elaborate acoustic display known as song, which becomes the dominant source of ambient underwater sound between December and April. Following reports of unusually low whale numbers that began in 2015/16, we examined song chorusing recorded through long-term passive acoustic monitoring at 6 sites off Maui as a proxy for relative whale abundance between 2014 and 2019. Daily root-mean-square sound pressure levels (RMS SPLs) were calculated to compare variations in low-frequency acoustic energy (0−1.5 kHz). After 2014/15, the overall RMS SPLs decreased between 5.6 and 9.7 dB re 1 μPa 2 during the peak of whale season (February and March), reducing ambient acoustic energy from chorusing by over 50%. This change in song levels co-occurred with a broad-scale oceanic heat wave in the northeast Pacific termed the 'Blob,' a major El Niño event in the North Pacific, and a warming period in the Pacific Decadal Oscillation cycle. Although it remains unclear whether our observations reflect a decrease in population size, a change in migration patterns, a shift in distribution to other areas, a change in the behavior of males, or some combination of these, our results indicate that continued monitoring and further studies of humpback whales throughout the North Pacific are warranted to better understand the fluctuations occurring in this recently recovered population and other populations that continue to be endangered or threatened.

Journal of the Acoustical Society of America, Oct 1, 2016

Each winter, thousands of humpback whales (Megaptera novaeangliae) migrate from their high latitu... more Each winter, thousands of humpback whales (Megaptera novaeangliae) migrate from their high latitude feeding grounds in Alaska to mate and calve in the shallow tropical waters around the Main Hawaiian Islands. Population estimates suggest that up to 10,000 animals winter in Hawaiian waters, making up more than half of the total North Pacific stock. However, in the 2015/16 season, anecdotal reports from commercial operators and researchers tell of an unusually low number of whales compared to previous years off the island of Maui. To examine this issue, data from long-term passive acoustic monitoring with autonomous Ecological Acoustic Recorders (EARs) during the 2014/15 and 2015/16 seasons off the west coast of Maui were analyzed using male chorusing levels as a proxy for relative whale abundance. Root-mean-square sound pressure levels (SPLs) were calculated to compare low frequency acoustic energy (0-1.56 kHz) between both seasons. The data showed that chorusing levels dropped in early January 2016. Although levels subsequently increased again until they peaked in February as expected, SPLs remained lower than in 2014/15 throughout the remaining season. These results suggest that the number of singing males was indeed lower during the 2015/16 season off west Maui and that future monitoring is warranted.

Coral Reefs, Nov 13, 2017

Coral reefs are characterized by high biodiversity and evidence suggests that reef soundscapes re... more Coral reefs are characterized by high biodiversity and evidence suggests that reef soundscapes reflect local species assemblages. To investigate how sounds produced on a given reef relate to abiotic and biotic parameters and how that relationship may change over time, an observational study was conducted between September 2014 and January 2016 at seven Hawaiian reefs that varied in coral cover, rugosity, and fish assemblages. The reefs were equipped with temperature loggers and acoustic recording devices that recorded on a 10% duty cycle. Benthic and fish visual survey data were collected four times over the course of the study. On average, reefs ranged from 0 to 80% live coral cover, although changes between surveys were noted, in particular during the major El Niño-related bleaching event of October 2015. Acoustic analyses focused on two frequency bands (50-1200 Hz and 1.8-20.5 kHz) that corresponded to the dominant spectral features of the major sound-producing taxa on these reefs, fish and snapping shrimp, respectively. In the low-frequency band, the presence of humpback whales (December-May) was a major contributor to sound level, whereas in the high-frequency band sound level closely tracked water temperature. On shorter timescales, the magnitude of the diel trend in sound production was greater than that of the lunar trend, but both varied in strength among reefs, which may reflect differences in the species assemblages present. Results indicated that the magnitude of the diel trend was related to fish densities at low frequencies and coral cover at high frequencies; however, the strength of these relationships varied by season. Thus, long-term acoustic recordings capture the substantial acoustic variability present in coral-reef ecosystems and provide insight into the presence and relative abundance of sound-producing organisms.

Journal of the Acoustical Society of America, Apr 1, 2022

The Hawaiian islands are home to more than 20 species of cetaceans and are the principal breeding... more The Hawaiian islands are home to more than 20 species of cetaceans and are the principal breeding ground of the north Pacific humpback whale population. The archipelago stretches more than 2500 km from Hawaii Island to Kure Atoll, creating a significant challenge for monitoring the occurrence and distribution of cetaceans across such a vast range. To meet this challenge, the National Oceanic and Atmospheric Administration and the U.S. Navy have been engaged in a three-year effort to monitor the marine soundscape of the Hawaiian archipelago known as the SanctSound Project. Bottom-moored acoustic recorders were deployed at multiple locations across the Hawaiian Islands Humpback Whale National Marine Sanctuary and the Papahānaumokuākea Marine National Monument to examine the occurrence of humpback whales and odontocetes based on the relative prevalence of their acoustic signaling. Anthropogenic sound sources were also studied to understand how these co-occur with cetaceans. Substantial spatial and temporal variability was observed in the prevalence of whale song and dolphin acoustic activity across locations with high cetacean presence sometimes overlapped with elevated anthropogenic activity. This work helps expand our understanding of how cetaceans use the archipelago and builds on the legacy of Whitlow Au, who pioneered cetacean acoustic monitoring in Hawaii.

Frontiers in Marine Science, Jan 26, 2023

The occurrence of humpback whales (Megaptera novaeangliae) across the 2600 km of Hawaiian archipe... more The occurrence of humpback whales (Megaptera novaeangliae) across the 2600 km of Hawaiian archipelago, which include the remote atolls, banks, and seamounts of Papahanaumokuakea Marine National Monument (PMNM), remains poorly understood. Previous surveys for humpback whales beyond the main Hawaiian Islands have been scarce due to limited access and the challenging winter conditions typically found in PMNM when whales are present. To overcome these limitations, a combination of moored acoustic recorders and a Wave Glider autonomous surface vehicle were used to acoustically monitor eight locations and survey approximately 1500 km of the Hawaiian archipelago for the occurrence of humpback whale song during the 2019-2020 breeding season. Relative song prevalence was established using a machine learning tool and by quantifying the level of song chorusing. A generalized additive model framework was applied to understand the associations between habitat variables and humpback whale song occurrence, and sound propagation modeling was performed to examine whether acoustic propagation influenced observed patterns. Whale song was recorded at all monitored and surveyed locations across the archipelago, albeit in varying amounts. Among the locations monitored with moored recorders, the highest and most sustained seasonal chorusing levels were measured off Maui followed by French Frigate Shoals (Kanemilohai),

Proceedings of Meetings on Acoustics, 2016

Coral reef soundscapes are dynamic, demonstrating amplitude and spectral variability across times... more Coral reef soundscapes are dynamic, demonstrating amplitude and spectral variability across timescales from seconds to seasons. Some of this variability can result from spatiotemporally heterogeneous patterns of human activity. To characterize this variability and the extent to which anthropogenic sound can modify the biological soundscape, seven Hawaiian reefs were equipped with acoustic recorders operating on a 10% duty cycle for 16 months. Spatially, vessel activity was acoustically detected unevenly across reefs; for example, vessels were acoustically present almost every day at a popular snorkeling reef but were rare in a protected area closed to boats, which indicates that exposure of reef fauna to vessel noise will vary by reef. Temporally, vessel activity was most likely to occur during daylight hours, which is consistent with patterns of human activity. This heterogeneity in exposure could have implications for physiology and behavior and underscores the need for long-term acoustic monitoring alongside more targeted studies investigating the potential for effects of noise on aquatic organisms.

Journal of the Acoustical Society of America, Oct 1, 2021

Journal of the Acoustical Society of America, Oct 1, 2017

Biological sounds occurring on coral reefs are increasingly recognized as important factors influ... more Biological sounds occurring on coral reefs are increasingly recognized as important factors influencing reef dynamics and ecological processes. Soundscapes of coral reefs can be broadly divided into a low-frequency band (<1 kHz), dominated by sounds produced by acoustically active fish, and a high-frequency band (2–20 kHz) dominated by snapping shrimp and other invertebrates. Because acoustic activities in both bands are influenced by a variety of ecological (biotic) and environmental (abiotic) factors, coral reef soundscapes are characterized by considerable spatial and temporal variability. The drivers of this variability are not yet well understood, but likely provide important insights into ecosystem processes and condition. We report on an effort to quantify the acoustic activity in both the fish and snapping shrimp frequency bands across twelve coral reef sites in the Pacific Ocean separated by distances ranging from hundreds of meters to thousands of kilometers, including reefs across the Hawaiian Archipelago, the Northern Mariana Islands, and American Samoa. We use data obtained from long-term, bottom-moored acoustic recorders to document the variability observed on multiple temporal scales and examine environmental drivers correlated with this variability at each location and differences among locations.

Frontiers in Marine Science, Dec 23, 2021

Passive acoustic monitoring (PAM) with autonomous bottom-moored recorders is widely used to study... more Passive acoustic monitoring (PAM) with autonomous bottom-moored recorders is widely used to study cetacean occurrence, distribution and behaviors, as it is less affected by factors that limit other observation methods (e.g., vessel, land and aerial-based surveys) such as inclement weather, sighting conditions, or remoteness of study sites. During the winter months in Hawai'i, humpback whale male song chorusing becomes the predominant contributor to the local soundscape and previous studies showed a strong seasonal pattern, suggesting a correlation with relative whale abundance. However, the relationship between chorusing levels and abundance, including non-singing whales, is still poorly understood. To investigate how accurately acoustic monitoring of singing humpback whales tracks their abundance, and therefore is a viable tool for studying whale ecology and population trends, we collected long-term PAM data from three bottom-moored Ecological Acoustic Recorders off west Maui, Hawaii during the winter and spring months of 2016-2021. We calculated daily medians of root-mean-square sound pressure levels (RMS SPL) of the low frequency acoustic energy (0-1.5 kHz) as a measure of cumulative chorusing intensity. In addition, between December and April we conducted a total of 26 vessel-based line-transect surveys during the 2018/19 through 2020/21 seasons and weekly visual surveys (n = 74) from a land-based station between 2016 and 2020, in which the location of sighted whale pods was determined with a theodolite. Combining the visual and acoustic data, we found a strong positive second-order polynomial correlation between SPLs and abundance (land: 0.72 ≤ R 2 ≤ 0.75, vessel: 0.81 ≤ R 2 ≤ 0.85 for three different PAM locations; Generalized Linear Model: p land 0.001, p vessel 0.001) that was independent from recording location (p land = 0.23, p vessel = 0.9880). Our findings demonstrate that PAM is a relatively low-cost, robust complement and alternative for studying and monitoring humpback whales in their breeding grounds that is able to capture smallscale fluctuations during the season and can inform managers about population trends in a timely manner. It also has the potential to be adapted for use in other regions that have previously presented challenges due to their remoteness or other limitations for conducting traditional surveys.

Frontiers in marine science, Mar 6, 2024

Marine Mammal Science, Nov 1, 2023

Springer eBooks, Dec 31, 2022

Research Square (Research Square), Oct 29, 2023

Journal of the Acoustical Society of America, Oct 1, 2016

Royal Society Open Science, Dec 1, 2017

Frontiers in remote sensing, Dec 12, 2022

Proceedings of Meetings on Acoustics, 2019

Endangered Species Research, Dec 17, 2020

Journal of the Acoustical Society of America, Oct 1, 2016

Coral Reefs, Nov 13, 2017

Journal of the Acoustical Society of America, Apr 1, 2022

Frontiers in Marine Science, Jan 26, 2023

Proceedings of Meetings on Acoustics, 2016

Journal of the Acoustical Society of America, Oct 1, 2021

Journal of the Acoustical Society of America, Oct 1, 2017

Frontiers in Marine Science, Dec 23, 2021