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Impacts of Anthropogenic Sound on Cetaceans
Abstract
Anthropogenic sound is created in the ocean both purposefully and unintentionally. The result is noise pollution that is high-intensity and acute, as well as lower-level and chronic. The locations of noise pollution are along well-traveled paths in the sea and particularly encompass coastal and continental shelf waters, areas that represent critical marine mammal habitat. The problem is one of isolation and a lack of awareness between humans who use the sea and marine mammals that inhabit the sea. Increased use of the sea for commercial shipping, geophysical exploration, and advanced warfare has resulted in a higher level of noise pollution over the past few decades. Informed estimates suggest that noise levels are at least 10 times higher today than they were a few decades ago. Without some effort to reduce or at least cap these noise levels , future ocean noise levels are likely to increase and further degrade the acoustic environment. A long-term monitoring program is needed to track future changes in ocean noise. Acoustic data should be included in global ocean observing systems now being planned by U.S. and international research foundations. Data from these monitoring systems should be openly available, and accessible to decision makers in industry, in the military, and in regulatory agencies. In tandem, a database should be developed to collect, organize and standardize data on ocean noise measurements and related anthropogenic activities. Currently, data regarding shipping, seismic exploration, oil and gas production, and other marine activities are either not collected or are difficult to obtain and analyze because they are maintained by separate organizations. Marine noise measurements and anthropogenic source data should be used to develop a global model of ocean noise. An important component of model development is better understanding of the characteristics for anthropogenic noise sources such as commercial shipping, arigun arrays, and military sonar. Research should be conducted relating the overall levels of anthropogenic activity (such as the types and numbers of vessels) with the resulting noise. Review of the evidence suggests that noise pollution is an important factor in the health of marine mammal habitats. There is sufficient evidence to conclude that high-intensity sounds are harmful and, on occasion, fatal to marine mammals. Behavioral data on marine mammal reaction to sound is complex, partially because of our meager abilities to observe marine mammal behavior in the wild. Evidence suggests that given the opportunity, marine mammals avoid high-intensity sound. Damage to marine mammal hearing due to anthropogenic sound exposure has been documented in the most extreme cases. Multiple mass- stranding events of beaked whales following high-intensity sound exposure demonstrate a repeated pattern of events. Following exposure to high-intensity sonar or airguns, beaked whales rapidly swim to the beach, and the animals die if not returned to the sea by human intervention. Those that are returned to the sea have an unknown fate. Understanding the causes and consequences of beaked whale mass stranding should be a high research priority. What is the mechanism for damage and/or disturbance? An impediment to assessing the biological effects of ocean noise is a continued lack of knowledge about marine mammal behavioral response to sound. Behavioral data must be collected in the wild to reveal potential effects. Significant ocean noise effects may be confined to a few individuals exposed at high sound pressure levels, and/or from widespread exposure at a population level. Discerning population level effects is challenging since the observations must be conducted over broad distances and long time periods. Our lack of understanding marine mammal behavioral reaction to sound is vast and must be addressed in the face of raising ocean noise levels. Research tools are needed to better observe marine mammal behavior in the wild. These are needed both to characterize normal behaviors and to detect changes in behavior associated with anthropogenic noise. Tools
... Several substantive reviews have considered ocean noise pollution in recent years (for example, Richardson et al., 1995;Simmonds et al., 2004;Hildebrand, 2005;Jasny, 2005;Weilgart, 2007;and Simmonds et al., 2014). The available evidence shows how noise can have a variety of deleterious effects on cetaceans, including: ■ reducing communication ranges and obscuring sounds of interest (a process known as masking); ■ disrupting reproductive behaviours; ■ adversely affecting energetic budgets through interference with foraging and increased travel; ■ excluding animals from certain important habitats; ■ inducing chronic stress responses; ■ causing temporary or permanent loss of hearing sensitivity; ■ inducement of physical injury; and, ■ in certain instances, causing mortality. ...
... Ocean noise sources generated by human activities can be divided into two main categories: ambient, continuous noise and intense, impulsive noise (Hildebrand, 2005;Simmonds et al., 2014). Ambient and continuous noise mainly relates to vessel traffic, including commercial shipping and passenger ferries as well as leisure boats. ...
... To a lesser extent, it is also used by researchers to gather other geological information. Arrays of airguns are deployed and fired with precise timing to produce a coherent pulse of sound (Hildebrand, 2005). Oil industry airgun arrays typically involve twelve to forty-eight individual guns, towed about 200m behind a vessel, and produce source levels as high as 260 dB peak re 1 µPa at 1 m output 1 (Hildebrand, 2009). ...
Cetaceans are highly adapted physiologically and behaviourally to use sound. As humans increasingly use sound underwater in our attempts to efficiently navigate, explore and exploit the seas, ocean noise pollution has become recognised as an issue of major significance and concern and a primary focus of marine mammal research over the last two decades. This has resulted in some relevant legislation, regional and international policy decisions, and associated guidance. Most current mitigation efforts are
directed at reducing the risk of injury from exposure to intense noise, although the effectiveness of such mitigation measures in terms of risk reduction has rarely been quantified. Longer-term chronic impacts of noise, including disturbance or masking of sounds critical for feeding and reproduction, have received substantially less attention.
The available evidence shows how noise can have a variety of deleterious effects on cetaceans, including:
■ reducing communication ranges and obscuring sounds of interest (a process known as masking);
■ disrupting reproductive behaviours;
■ adversely affecting energetic budgets through interference with foraging and increased travel;
■ excluding animals from certain important habitats;
■ inducing chronic stress responses;
■ causing temporary or permanent loss of hearing sensitivity;
■ inducement of physical injury; and,
■ in certain instances, causing mortality.
... Over the past century, as human beings are expanding their activities into the ocean frontier in an increasing pace, intense noises associated with these activities are also being introduced into the marine environment [2]. These noises often have adverse consequences to marine mammals, ranging from potential injury and mortality to hearing impairment and behavioral modification [2,3]. As a result, over the past 30 years or so, concerns related to ocean noise impacting marine life have been one of the most heatedly discussed topics among environmental issues, which in turn has been fueling many scientific studies [2,4]. ...
... The potential impacts of military sonar on marine mammals are probably one of the most controversial issues concerning underwater anthropogenic noises at this moment. This is because the use of military sonar, especially the mid-frequency anti-submarine warfare (ASW) tactical sonar, has been linked to several mass strandings of marine mammals, especially in the genera Ziphius and Mesoplodon [3,4,10]. Based on the frequency range, the U.S. military sonars are classified into three major groups: low-frequency (< 1 kHz) sonar, mid-frequency (1-20 kHz) sonar, and high-frequency (> 20 kHz) sonar [3,11]. ...
... This is because the use of military sonar, especially the mid-frequency anti-submarine warfare (ASW) tactical sonar, has been linked to several mass strandings of marine mammals, especially in the genera Ziphius and Mesoplodon [3,4,10]. Based on the frequency range, the U.S. military sonars are classified into three major groups: low-frequency (< 1 kHz) sonar, mid-frequency (1-20 kHz) sonar, and high-frequency (> 20 kHz) sonar [3,11]. Signals from ASW sonars can be either constant frequency (CF) or frequency modulated (FM). ...
Most animals inhabit the aquatic environment are acoustical-oriented, due to the physical characteristics of water that favors sound transmission. Many aquatic animals depend on underwater sound to navigate, communicate, find prey, and avoid predators. The degradation of underwater acoustic environment due to human activities is expected to affected these animals' well-being and survival at the population level. This dissertation presents three original studies on the characteristics and behavior of underwater sound fields in three unique marine environments with anthropogenic noises.
The first study examines the soundscape of the Chinese white dolphin habitat in Taiwan. Acoustic recordings were made at two coastal shallow water locations, Yunlin and Waisanding, in 2012. Results show that croaker choruses are dominant sound sources in the 1.2--2.4 kHz frequency band for both locations at night, and noises from container ships in the 150--300 Hz frequency band define the relative higher broadband sound levels at Yunlin. Results also illustrate interrelationships among different biotic, abiotic, and anthropogenic elements that shape the fine-scale soundscape in a coastal environment.
The second study investigates the inter-pulse sound field during an open-water seismic survey in coastal shallow waters of the Arctic. The research uses continuous acoustic recordings collected from one bottom-mounted hydrophone deployed in the Beaufort Sea in summer 2012. Two quantitative methods were developed to examine the inter-pulse sound field characteristics and its dependence on source distances. Results show that inter-pulse sound field could raise the ambient noise floor by as much as 9 dB, depending on ambient condition and source distance.
The third study examines the inter-ping sound field of simulated mid-frequency active sonar in deep waters off southern California in 2013 and 2014. The study used drifting acoustic recorder buoys to collect acoustic data during sonar playbacks. The results show strong band-limited elevation (13--24 dB) of sound pressure levels for over half of the inter-ping intervals above the natural background levels.
These three studies provide insights on the dynamics of marine soundscape and how anthropogenic activities can change the acoustic habitat by elevating the overall sound field levels.
... The traffic of motorized boats is one of the primary sources of disturbance for cetaceans Lemon et al., 2006). Motorboats increase the noise level in the ocean and change the acoustic environment of cetaceans (Hildebrand, 2005). For example, toothed whales are affected by sound interference, as they echolocate to perceive the surrounding environment and to find their prey. ...
... For example, toothed whales are affected by sound interference, as they echolocate to perceive the surrounding environment and to find their prey. Furthermore, toothed whales produce a complex vocal repertory to communicate (National Research Council, 2003;Au, 2004;Hildebrand, 2005). The boat traffic may drive this species off from areas they use to forage, rest, or reproduce (Parsons, 2012;Rako et al., 2013) and __________________ Corresponding editor: Jorge Urbán consequently reduce the time they allocate to these activities (Gill et al., 2001;Bejder et al., 2009). ...
... The boat traffic may drive this species off from areas they use to forage, rest, or reproduce (Parsons, 2012;Rako et al., 2013) and __________________ Corresponding editor: Jorge Urbán consequently reduce the time they allocate to these activities (Gill et al., 2001;Bejder et al., 2009). In addition, sound disturbances may affect hearing abilities of toothed whales either temporarily or permanently (Richardson & Würsig, 1997) and cause stress (Miksis et al., 2001;Romano et al., 2004;Hildebrand, 2005). Stress leads to metabolic rate variations, with an increase in energy production necessary for diving and swimming speed (Christiansen et al., 2014). ...
Boat engines increase the noise levels of the oceans, alter the acoustic environment of cetaceans and diminish their efficiency to echolocate. This study aims to determine if Guiana dolphins (Sotalia guianensis) are influenced by boat approaches. A land-based survey was conducted to record behavioral responses and count surfacing events of Guiana dolphins during 293 observation sessions from February to November 2014 in Pontal Bay, Ilhéus, Brazil. Ninety-eight behavioral responses to boat approaches of 93 dolphin groups were classified as negative (interruption or alteration of activity) or neutral (no response). The dolphins presented a neutral response to 90% of boats without engine approaches, 48% negative responses to inboard motorboat approaches, and 76% negative responses to outboard motor boat approach. Resting groups demonstrated 14 negatives and four neutral responses. Groups engaged in forage-feed activity presented ten negative and seven neutral responses while traveling groups exhibited 14 negative and 36 neutral responses. The average rate of surfacing events was significantly superior (P < 0.001) in the absence of boats (1.83 ± 0.90 surfacing events ind-1 min-1) than in their presence (1.34 ± 0.92 surfacing events/individual/minute). Guiana dolphins are exposed to an increasing number of anthropic perturbations and the evaluation of its behavioral responses to approaching boats is the first step to comprehend the real impact of boat encounters. Our results may contribute to the development of management strategies in estuarine areas to increase the conservation of the Guiana dolphins.
... For example, the massive blue whale (Balaenoptera musculus) produces low-frequency sounds down to ∼15 Hz, whereas on the other end of the spectrum, dolphins within the genus Cephalorhynchus can produce sounds up to 200 kHz (Tougaard and Kyhn, 2010). This broad range of frequencies overlaps with many of the sounds humans introduce into the water (intentionally or otherwise), including ship noise, sonars of various types, and seismic activities (Hildebrand, 2005). ...
... Sources of anthropogenic sound are becoming both more pervasive and more powerful, increasing both oceanic background noise levels and peak sound intensity levels. Anthropogenic activities in the ocean have increased over the past 50 years, resulting in more low-frequency (<1,000 Hz) and mid-frequency (1-20 kHz) noise (Hildebrand, 2005). There is growing concern that sound introduced into the sea by human activities can have detrimental effects on marine mammals. ...
... There is growing concern that sound introduced into the sea by human activities can have detrimental effects on marine mammals. For example, there is mounting evidence suggesting that high-intensity anthropogenic sound from sonar and airguns have resulted in the stranding and subsequent mortality of beaked whales (Ziphiidae) (Hildebrand, 2005). In recent years, public concern about the possible effects of anthropogenic environmental noise has grown steadily within the scientific and conservation communities (Würsig et al., 2000;Jefferson and Hung, 2004;Jefferson et al., 2009), which has resulted in more research on and attention to mitigating these adverse impacts. ...
Marine mammals with near-shore distributions are susceptible to human-related recreational and commercial disturbances, particularly near densely populated and industrialized coastal areas. A population of over 2,500 Chinese humpback dolphins (Sousa chinensis chinensis) occupies the Pearl River Estuary in southern China. A part of this population uses Hong Kong’s waters off of Lantau Island, where they are subjected to a number of anthropogenic threats, including vessel disturbance, fisheries interactions, and boat-based tourism. Previous research has shown that the abundance of this subspecies in Hong Kong’s waters has declined about 60% since 2003. Using a combination of acoustic recordings, dolphin distribution and abundance data, and vessel traffic information I found that: 1) Four types of vessels common to the waters on Hong Kong generate noise that is audible to Sousa chinensis chinensis; 2) The spatial distribution of underwater noise in Hong Kong’s waters does not significantly vary among the six sites sampled; 3) High-speed ferry traffic and passenger volume has increased dramatically during the study period; 4) There has been a significant decline in dolphin density in areas within and near vessel traffic; and 5) Dolphins are most at risk of vessel collisions and being exposed to vessel noise near Fan Lau and within the Urmston Road waterway just northeast of the Sha Chau and Lung Kwu Chau Marine Park . These results can inform future acoustic studies on this species and guide conservation and management efforts in Hong Kong.
... A number of reviews of anthropogenic sound in the oceans (and its effects on marine mammals) have described properties of underwater sound, outlined the differences between the transmission of sound underwater versus in air and compared acoustic characteristics associated with different types of anthropogenic sources (e.g., Hildebrand, 2005;MMC, 2007;Nowacek, Thorne, Johnston, & Tyack, 2007;NRC, 1994NRC, , 2003Richardson, Greene, Malme, & Thomson, 1995). This paper will not attempt to provide the same detailed coverage of these topics. ...
... Many of the various sources and their characteristics have been described in previous works (e.g., Hildebrand, 2005;Nowacek et al., 2007;NRC, 1994NRC, , 2003Richardson et al., 1995). Therefore, here we shall focus on three source types that have drawn considerable recent attention: naval exercises, seismic surveys, and commercial shipping. ...
... Beaked whales have repeatedly mass-stranded a few hours to days after naval maneuvers during which military ships used midrange frequency sonar (Fernandez et al., 2005;Hildebrand, 2005) 1 . These whales were consistently affected by a new syndrome, never described in marine mammals prior to these events, consisting of extensive fat and gas bubble emboli: an ensemble of lesions most similar to decompression sickness in human divers Jepson et al., 2003). ...
... These whales were consistently affected by a new syndrome, never described in marine mammals prior to these events, consisting of extensive fat and gas bubble emboli: an ensemble of lesions most similar to decompression sickness in human divers Jepson et al., 2003). It is clear that the severity of emboli is the direct cause of death and that the constant temporal and spatial coincidence with naval exercises involving sonar designates these exercises as the cause of this new syndrome (Fernandez et al., 2005;Hildebrand, 2005). Recent studies have qualified beaked whales as the deepest diving mammals (down to 1.8 km: Tyack, Johnson, Aguilar Soto, Sturlese & Madsen, 2006) and have shown that these animals typically 1 With regards to the debate over the frequency of strandings coincident with such activities, it should be noted that the discovery of just one dead body from a wild population is widely accepted in terrestrial biology to be always indicative of a wider problem, as it is easy to miss carcasses (p14-15 in Wobeser, 1994). ...
... It has been suggested that a significant proportion of the ambient noise is due to activities of the oil and gas industries during the exploration, development, production and decommissioning phases. The transport of oil and gas related products accounts for nearly 50% of the gross shipping tonnage, despite using only 19% of the total number of vessels in the world's commercial fleet (McDonald et al., 2006;Hildebrand, 2005). ...
... The main problems associated with acoustic deterrents are the lack of long-term effectiveness and noise pollution, with a potential long-term effect on target and non-target species (Götz & Janik, 2013). AHDs produce sound levels high enough to cause hearing damage to marine mammals at close range (Hildebrand, 2005); hearing damage due to long cumulative exposure is also feasible (Götz & Janik, 2013). ...
Literature review of underwater sounds produced by the oil and gas industry. The report covers all the stages of the oil and gas lifecycle: exploration, development, production, and decommissioning. Among the acoustic sources addressed in the report are seismic sources, engineering sources, vessels, dredging, drilling, production activities, pipe laying and decommissioning.
... On the other hand, some continuous sources can be very powerful e.g. supertankers (Hildebrand, 2005;Southall et al., 2007;Southall et al., 2019). Figure 4 presents an overview of the respective frequency ranges for sound sources, which are split into natural and anthropogenic, with the latter split further into continuous and impulsive. ...
... Across all the impulsive sound sources, explosions produce the highest peak levels of noise. This is why there is serious risk of direct injury to marine organisms, which depends on the weight of the charge and the depth of the detonation (Hildebrand, 2005;OSPAR Commission, 2009b). ...
Anthropogenic underwater noise impacts have become a hot topic for environmental managers and regulators in Europeand beyond. Sounds from human activity at sea include shipping and other marine craft, construction and installations, sonar and seismic surveys. This Future Science Brief presents an update on the previous EMB publication on underwater noise, Position Paper N° 13 on “The effects of anthropogenic sound on marine mammals: A draft research strategy". This Future Science Brief expands the scope of the discussion beyond marine mammals to fishes and invertebrates, and outlines key developments that have taken place since the Position Paper’s publication. The main chapters of the document focus on: the advances in our knowledge on anthropogenic underwater sound in the Ocean; the new knowledge that has been developed on the effects of noise on marine organisms; and the measures that have been taken to address the issue of underwater noise.
While significant progress has been made, knowledge gaps still remain. The document therefore presents these outstanding issues and highlights priority actions for addressing them. This Future Science Brief states that the most urgent priority actions/questions are to:
1. Develop collaborative international standards applicable to all steps of the risk framework;
2. Conduct comprehensive monitoring combined with spatial ecological modelling of marine species’ dynamic habitat use, movements, behaviour and distribution to establish baselines;
3. Foster comprehensive monitoring and data collection of current soundscapes / ambient noise, including via joint monitoring programmes in existing and new areas;
4. Shortlist high priority (and biologically relevant) sound sources and perform standardized source characterization studies;
5. Undertake hearing studies on baleen whales and on selected fish and invertebrate species;
6. Conduct field and modelling studies on changes in acoustic habitats to identify masking risks to communication in fishes and marine mammals;
7. Conduct further studies on behavioural response of marine mammals and fishes due to exposure to high intensity impulsive sounds to assess population consequences;
8. Conduct taxa-relevant studies on hearing impairment and physiological stress to address existing knowledge gaps in invertebrates, fishes and marine mammals;
9. Conduct dedicated studies including multi-species investigations, predator-prey interactions, and interaction with other food web levels, addressing the question of how noise impacts combine with other stressors;
10. Develop frameworks and conduct studies to allow population-level assessment of effects from cumulative impact of noise and other pressures;
11. Conduct dedicated modelling and field studies to improve understanding on effectiveness, safety and cost-effectiveness of noise mitigation devices, mitigation measures and management options;
12. Develop regional action plans and guidelines for Environmental Impact Assessment and policies; and
13. Initiate international collaborative transdisciplinary projects to develop stakeholder and societal capacity in understanding and addressing underwater noise.
... Sound is centrally important for many marine taxa as hearing is among the most vital of the senses for underwater life (Tyack, 1998;Hildebrand, 2005;Hawkins and Popper, 2017;Southall, 2017). Sound is critical to foraging, communication, predator avoidance, and general spatial orientation for marine mammals, fish, sea turtles, and invertebrates (Tolimieri et al., 2000;Staaterman et al., 2012;Williams et al., 2015). ...
... Here we provide a synthesis of technical guidance; policy frameworks; declarations; implementation programs and projects; and recommendations/guidelines related to noise reduction that have been adopted or otherwise endorsed by intergovernmental policy fora, individual governments, and international agreements/organizations, as well as information on ongoing mitigation efforts led by regional organizations and state/local governments. We do not review the science of noise and its impacts, as there are already multiple published and thorough reviews (e.g., NRC, 2003;Hildebrand, 2005;NRC, 2005;Nowacek et al., 2007;Weilgart, 2007;Clark et al., 2009;Popper and Hawkins, 2012;Southall, 2017). Rather, this synthesis draws on written submissions voluntarily provided to the United Nations Division for Ocean Affairs and the Law of the Sea in advance of the nineteenth meeting of the United Nations Open-ended Informal Consultative Process on Oceans and the Law of the Sea (UN ICP), 1 and related programs derived from those parties, to highlight ongoing efforts on: 1) noise assessment and monitoring; 2) noise mitigation; and 3) noise reduction programs/projects. ...
Anthropogenic underwater noise levels have generally increased as industrial activities in the ocean have become more prevalent. Because of the central nature of sound in the lives of many marine animals, and the known and potential adverse impacts of noise, it is also gaining increased international recognition as an important global conservation issue. Here, a current compilation and synthesis of official documents, reports, and strategic plans from various intergovernmental, governmental, and international organizations, and noise-related projects and programs, demonstrate increasing efforts to understand anthropogenic underwater noise, and the mitigation and management measures that are being considered to reduce noise. While some entities aim to better understand and quantify underwater noise and its impacts, others have recommended explicit mitigation measures including spatio-temporal approaches to managing noise sources, and vessel quieting technologies. New approaches also include the development of certification or voluntary noise-reduction programs and agreements. We highlight four considerations that will better link the potential impacts of noise with corresponding mitigation and noise reducing efforts: 1) collaboration to address the transboundary and cumulative nature of underwater noise; 2) differing countries’ implementation capabilities for addressing noise; 3) time and intensity tradeoffs (e.g., louder noise for a shorter time period versus quieter but for longer); and 4) variable noise impacts depending on specific life history stages and life functions. Our review affirms the international consensus that anthropogenic underwater noise is a currently pervasive yet relatively transient form of pollution, the effects of which can be significantly reduced through effective mitigation and regulatory action.
... Additionally, groups of marine mammals containing calves are more responsive to vessel noise, altering respiration, diving, swimming, and aerial behaviour (Bauer et al. 1993;Blane and Jaakson 1994). Noise pollution can cause marine mammals to alter their behaviour by directly disturbing them (Aguilar Burns and Seaman 1986;Cosens and Dueck 1988;Finley et al. 1990) or by masking their acoustic signals over large areas (Hildebrand 2005;Norman 2011;Payne and Webb 1971;Richardson et al. 1995;Scharf 1970;Weilgart 2007); loud sounds may directly affect their hearing abilities by producing either temporary or permanent hearing loss (Gordon and Tyack 2002;National Research Council 2000Richardson et al. 1995;Simmonds and Lopez-Jurado 1991). All these effects may be critical for the survival of marine mammals. ...
... Documented responses of fish include: physiological effects such as elevated heart rate, secretion of stress hormones, and increased metabolism and motility (Popper 2003). For marine mammals, effects can include: physiological effects (such as elevated heart rate, secretion of stress hormones) (Reeves et al. 2012;Rolland et al. 2017), behavioural changes (avoidance, diving pattern changes), displacement from habitats (Tyack 2008), and masking or interfering with vocalizations made for communication and sensation (which can disrupt feeding) (Hildebrand 2005;Jasny et al. 2005;Lacy et al. 2015;National Research Council 2005). For animals exhibiting these responses, the effects of anthropogenic noise represent a loss of acoustic habitat. ...
Vessels involved in commercial marine shipping in Canada engage in the movement of goods or people by sea on the Arctic, Atlantic, and Pacific oceans. To explore the ways that the activities associated with commercial shipping can impact the marine environment, a suite of activity-based Pathways of Effects (PoE) conceptual models were developed. PoE conceptual models describe the pathways (linkages) between human activities, associated stressors, and their effects on endpoints, based on current knowledge. A visual representation of each PoE model is supported by text describing each pathway linkage based on scientific literature or expert opinion. Indigenous and local knowledge were not used in the current work. PoE models are useful tools for the scoping phase of a variety of environmental assessment, such as ecological risk assessment, environmental impact assessment, and cumulative effect assessments as they clearly outline activities and stressors and clarify connections between human activities and potential effects on ecological endpoints, and provide a science-based foundation for decision-making. The objective of these models and their supporting evidence is to provide a systematic review of the effects of shipping-associated activities on marine ecosystems. PoE models have been developed for five activities associated with commercial marine shipping in Canada: 1) anchoring and mooring, 2) vessel at rest, 3) grounding and sinking, 4) movement underway, and 5) discharge (divided into two PoE models: ‘debris’ and ‘other’). The PoEs were developed to be broad enough to be adapted for application in a range of environments and locations and detail the potential stressors and effects that could be considered in an assessment. The activity-based PoE models contain fourteen stressors (e.g., substrate disturbance, vessel strikes) and are related to three effects (change in fitness, mortality, and change in habitat) on ten generic endpoints (e.g., marine mammals, physical habitat). The models only include activities related to the commercial movement of goods and people by vessels, not included in this document are other vessel activities such as fishing, seismic surveying, dredging, port operations (e.g., when at-berth and while berthing). Non-commercial vessels (e.g., recreational vessels) are also not specifically included in these models. Though endpoints have been identified for illustrative purposes here, ultimately the assessor is responsible for comprehensively scoping the specific endpoints (e.g., valued components) and stressors to be considered in any assessment. PoE models do not include any evaluation of the relative or absolute impact from these activities on specific endpoints; this would occur in a subsequent assessment step, such as risk assessment.
... Communication sounds play a role in mating, feeding, and group social cohesion, and echolocation clicks might also broadcast information to conspecifics such as the direction of travel (Miller, 2002;Lammers and Au, 2003). Human activities such as commercial shipping, military exercises, and pile-driving produce noise that might interfere with odontocete communication (Richardson et al., 1995;Hildebrand, 2005;Erbe et al., 2016). To predict potential acoustic impacts on odontocetes due to anthropogenic noise, it is necessary to better understand how sounds below $30 kHz are received; especially how they vary with the orientation of the animal's body relative to the sound source, i.e., receiving beam pattern or directionality. ...
... Directional hearing allows the listener to separate a signal from noise based on the spatial location of the signal and noise sources (spatial release from masking). Humangenerated (anthropogenic) sounds can potentially mask the wide variety of social and foraging sounds that are critical for the survival of dolphins in their natural environment (Richardson et al., 1995;Hildebrand, 2005;Erbe et al., 2016). Naval, oceanographic, construction, and seismic exploration activities can produce very high-amplitude, lowfrequency sounds (Mulroy, 1991), but the effects of these activities on marine mammals are often difficult to predict because the existing data do not include directional considerations (Clark et al., 2009). ...
Bottlenose dolphins (Tursiops truncatus) depend on sounds with frequencies <30 kHz for social communication and foraging, but little information on the directional dependence of hearing thresholds for these sounds exists. This study measured behavioral hearing thresholds for 2, 10, 20, and 30-kHz tones projected from eight different angular positions around the dolphin in both the horizontal and vertical planes to determine whether the receiving beam at these frequencies was directional. Omni-directional hearing was hypothesized for sounds below 30 kHz, but this hypothesis was rejected. Results from two bottlenose dolphins demonstrated a positive relationship between directivity and the frequency of the test tone, with asymmetric beam patterns. Directional hearing sensitivity declined most dramatically between 10 kHz and 2 kHz. The results suggest that dolphins’ directional hearing is more pronounced for lower frequencies than previously predicted.
... This confirms that the contribution of submarine volcanic activity at Ahyi to the ocean soundscape is indeed substantial. For example, acoustic energy released at the volcano supersedes the projected annual input from seismic surveying by a factor of two (3.9 10 13 J, Hildebrand, 2005) and is almost four times higher than previous estimates for the cumulative energy of all sonar activities in the global ocean combined (2.6 10 13 J, Hildebrand, 2005). However, unlike underwater noise produced by sonar, ship traffic and seismic surveying, volcanic episodes represent intense, yet localized and often short-lived events. ...
... This confirms that the contribution of submarine volcanic activity at Ahyi to the ocean soundscape is indeed substantial. For example, acoustic energy released at the volcano supersedes the projected annual input from seismic surveying by a factor of two (3.9 10 13 J, Hildebrand, 2005) and is almost four times higher than previous estimates for the cumulative energy of all sonar activities in the global ocean combined (2.6 10 13 J, Hildebrand, 2005). However, unlike underwater noise produced by sonar, ship traffic and seismic surveying, volcanic episodes represent intense, yet localized and often short-lived events. ...
Ahyi is a fully submerged arc volcano in the Northern Mariana Islands, northwestern Pacific Ocean. In April and May 2014, the volcano erupted over a period of 15 days. Results from direction-of-arrival calculations show that underwater sound phases associated with the episode were recorded as far as Wake Island, where a hydrophone triplet array is operated as part of the International Monitoring System. After a 3.5-hr-long sequence of hydroacoustic precursory events, explosive volcanic activity occurred in two distinct, several-days-long bursts, accompanied by a notable decrease in low-frequency arrivals that may indicate a shift in signal source parameters. Acoustic resolution of the hydrophone data supersedes broadband networks by almost 1 order of magnitude, successfully identifying seismic events at Ahyi as low as 2.5 mb. Total radiated acoustic energy of the eruption is estimated at 9.7 10¹³ J, which suggests that submarine volcanic activity contributed significantly to the ocean soundscape.
... Most fish finding sonars operate in the 20-200 kHz range with source levels of 150-235dB re 1μ PA [15]. These relatively low frequency sonars can penetrate bodies and detect swim bladders, lungs, etc. [14]. ...
... Although marine mammals have been detected at times to be drifting with the tide, when the whole track is considered there are usually several subsequent steps that identify self-propulsion. This subject is an area of ongoing research in examining animals' interactions with the local environments as well as longer migratory paths [15], [17], [18]. For example, Keyser at al. [12] identified that striped bass in the Minas Passage, Bay of Fundy, exhibited reduced diel vertical migration as water temperature decreased to sub-zero conditions, and may have been somewhat lethargic, and moving more passively with the tides. ...
... 1. anthropogenic causes such as shooting, entanglement, ingestion of debris, and collision with boats [2], as well as anthropogenic sound and naval activities [7]; 2. predation by the animals' natural predators (such as shark attacks); 3. disease, of which there are numerous varieties known to affect marine mammals such as herpes virus, Leptospirosis and others; 4. toxins (whether natural toxins or anthropogenic pollutants); 5. lack of food and/or inexperience of young animals; and, finally, 6. oceanographic or environmental causes, such as changes in prey distribution due to El Niño events. ...
... anthropogenic causes such as shooting, entanglement, ingestion of debris, and collision with boats [2], as well as anthropogenic sound and naval activities [7]; 2. ...
The causes of marine mammals stranding on coastal beaches are not well understood, but may relate to topography, currents, wind, water temperature, disease, toxic algal blooms, and anthropogenic activity. Offshore earthquakes are a source of intense sound and disturbance and could be a contributing factor to stranding probability. We tested the hypothesis that the probability of marine mammal stranding events on the coasts of Washington and Oregon, USA is increased by the occurrence of offshore earthquakes in the nearby Cascadia subduction zone. The analysis carried out here indicated that earthquakes are at most, a very minor predictor of either single, or large (six or more animals) stranding events, at least for the study period and location. We also tested whether earthquakes inhibit stranding and again, there was no link. Although we did not find a substantial association of earthquakes with strandings in this study, it is likely that there are many factors influencing stranding of marine mammals and a single cause is unlikely to be responsible. Analysis of a subset of data for which detailed descriptions were available showed that most live stranded animals were pups, calves, or juveniles, and in the case of dead stranded mammals, the commonest cause of death was trauma, disease, and emaciation.
... An international working group (Spain-United Kingdom) should propose appropriate management measures that, at least, prevent or restrict navigation, prohibit bluefin tuna fishing (in any of its modalities) within the interior critical habitat. This would not only help reduce interactions and collisions with the animals but would also protect them from the strong noise pollution generated by motorboats, already sufficiently demonstrated in previous research for cetaceans in general (Hildebrand, 2004), and, more specifically, for the species object of this paper (Aroyan, 2001;Berrow et al., 2008;Jepson et al., 2013). ...
Delphinus delphis Linnaeus 1758 is considered an endangered species in the Mediterranean. The species is resident in the Bay of Algeciras - Gibraltar (southern Spain; waters partially shared with Gibraltar, UK). This area is subject to strong anthropogenic pressure, but with an input of renewed waters in its central area. During three consecutive years (March 2017–March 2020), sightings were observed concentrated along the submarine canyon that runs north to south across the bay, forming a “specular S″ with a maximum depth of 460 m. The pods of Dd showed a continuous or semi-continuous spatial distribution along the vertical axis of the submarine canyon, where they feed, mate, breed and rear calves in a well-defined area that constitutes a critical habitat. This area has been cartographically delimited, choosing the area of maximum dolphin frequency as highly vulnerable due to the possibility of collisions with small vessels (<15 m) and interactions with sport fishing activities (popping, ballooning, trolling) which constitute the main threat counting the derived impacts from noise pollution. Spatio-temporal mapping has been developed to visualize the overlapping between the dolphin groups and small vessels. Mapping analysis has shown that an international Spanish-British micro-sanctuary urgently needs to be established in order to create a protected area specifically for the common dolphins, and for other species which inhabit/use the waters between Spain and Gibraltar. Coordinates and a delimited surface area have been proposed in this paper.
... An international working group (Spain-United Kingdom) should propose appropriate management measures that, at least, prevent or restrict navigation, prohibit bluefin tuna fishing (in any of its modalities) within the interior critical habitat. This would not only help reduce interactions and collisions with the animals but would also protect them from the strong noise pollution generated by motorboats, already sufficiently demonstrated in previous research for cetaceans in general (Hildebrand, 2004), and, more specifically, for the species object of this paper (Aroyan, 2001;Berrow et al., 2008;Jepson et al., 2013). ...
Delphinus delphis Linnaeus 1758 is considered an endangered species in the Mediterranean. The species is resident in the Bay of Algeciras - Gibraltar (southern Spain; waters partially shared with Gibraltar, UK). This area is subject to strong anthropogenic pressure, but with an input of renewed waters in its central area. During three consecutive years (March 2017–March 2020), sightings were observed concentrated along the submarine canyon that runs north to south across the bay, forming a “specular S″ with a maximum depth of 460 m. The pods of Dd showed a continuous or semi-continuous spatial distribution along the vertical axis of the submarine canyon, where they feed, mate, breed and rear calves in a well-defined area that constitutes a critical habitat. This area has been cartographically delimited, choosing the area of maximum dolphin frequency as highly vulnerable due to the possibility of collisions with small vessels (<15 m) and interactions with sport fishing activities (popping, ballooning, trolling) which constitute the main threat counting the derived impacts from noise pollution. Spatio-temporal mapping has been developed to visualize the overlapping between the dolphin groups and small vessels. Mapping analysis has shown that an international Spanish-British micro-sanctuary urgently needs to be established in order to create a protected area specifically for the common dolphins, and for other species which inhabit/use the waters between Spain and Gibraltar. Coordinates and a delimited surface area have been proposed in this paper.
... An international working group (Spain-United Kingdom) should propose appropriate management measures that, at least, prevent or restrict navigation, prohibit bluefin tuna fishing (in any of its modalities) within the interior critical habitat. This would not only help reduce interactions and collisions with the animals but would also protect them from the strong noise pollution generated by motorboats, already sufficiently demonstrated in previous research for cetaceans in general (Hildebrand, 2004), and, more specifically, for the species object of this paper (Aroyan, 2001;Berrow et al., 2008;Jepson et al., 2013). ...
... Despite these concerns, the link between diving behaviour and possible injury from noise exposure is limited for most marine mammals. To date, the connection has been based primarily on the potential for unexpected noise to elicit unusual swimming behaviours and physical exertion Goldbogen et al., 2013;Hildebrand, 2005;Richardson et al., 1995;Southall et al., 2016). ...
Limited polar geographical range, narrowly defined migratory routes, and deep‐diving behaviors make narwhals exceptionally vulnerable to anthropogenic disturbances including oceanic noise. Although behavioral studies indicate marked responses of cetaceans to disturbance, the link between fear reactions and possible injury from noise exposure is limited for most species. To address this, we deployed custom‐made heart rate‐accelerometer‐depth recorders on 13 adult narwhals in Scoresby Sound, East Greenland across a five‐year period (2014‐2018). Physiological responses of the cetaceans were monitored in the absence (n = 13 animals) or presence (n = 2 animals across 3 acoustic events) of experimentally directed, seismic airgun pulses and associated vessels (full volume source level = 241 dB re 1 μPa‐m). We found that anthropogenic noise resulted in marked cardiovascular, respiratory and locomotor reactions by two narwhals exposed to seismic pulses across three acoustic events. The general behavioral response to seismic and vessel noise included an 80% reduction in the duration of gliding during dive descents by seismic‐exposed narwhals compared to controls, and the prolongation of high intensity activity (ODBA > 0.20 g) with elevated stroke frequencies exceeding 40 strokes per minute. Noise exposure also resulted intense (< 10 bpm) bradycardia that was decoupled from stroking frequency. This decoupling instigated increased variability in heart rate, with the heart switching rapidly between bradycardia and exercise tachycardia during noise exposure. Maximum respiratory frequency following seismic exposure, 12 breaths.min‐1, was 1.5 times control levels. Overall, the effect of seismic/ship noise exposure on Arctic narwhals was a 2.0 – 2.2‐fold increase in the energetic cost of diving, which paradoxically occurred during suppression of the cardiac exercise response. This unusual relationship between diving heart rate and exercise intensity represents a new metric for characterizing the level of fear reactions of wild marine mammals exposed to different environmental stressors. Together, the multi‐level reactions to anthropogenic noise by this deep‐diving cetacean demonstrated how a cascade of effects along the entire oxygen pathway could challenge physiological homeostasis especially if disturbance is prolonged.
... Therefore, as V varies for different scenarios the convergence time t c will also vary inversely. However, normalised time and distance cannot account for changes in Q (e.g., supertankers have much lower f c than UUVs [42]) or the sensor separation D which can affect the convergence performance. Therefore, a sensitivity analysis was performed in which Q and sensor separation D were varied for SNR 0 = 10 dB. Figure 4 shows the normalised median time to convergence for different values of Q and D λ c computed over (N r = 100) repeats. ...
Particle swarm optimisation (PSO) is a swarm intelligence algorithm used for controlling robotic swarms in applications such as source localisation. However, conventional PSO algorithms consider only the intensity of the received signal. Wavefield signals, such as propagating underwater acoustic waves, permit the measurement of higher order statistics that can be used to provide additional information about the location of the source and thus improve overall swarm performance. Wavefield correlation techniques that make use of such information are already used in multi-element hydrophone array systems for the localisation of underwater marine sources. Additionally, the simplest model of a multi-element array (a two-element array) is characterised by operational simplicity and low-cost, which matches the ethos of robotic swarms. Thus, in this paper, three novel approaches are introduced that enable PSO to consider the higher order statistics available in wavefield measurements. In simulations, they are shown to outperform the standard intensity-based PSO in terms of robustness to low signal-to-noise ratio (SNR) and convergence speed. The best performing approach, cross-correlation bearing PSO (XB-PSO), is capable of converging to the source from as low as −5 dB initial SNR. The original PSO algorithm only manages to converge at 10 dB and at this SNR, XB-PSO converges 4 times faster.
... The energy resulting from the bubble pulses will act cumulatively with the energy from the initial shock wave, contributing~5 dB to the source level ( [20,21]), giving SL pk = 269 + 5 + 7.533 log 10 0.4536W TNTeq (9) and there will be an almost constant frequency content between 10 and 200 Hz. The sounds from an explosion propagate equally in all directions. ...
A simple underwater noise model suitable for use with explosives in the decommissioning of oil and gas subsea structures is introduced and evaluated against data from five projects in the US. The performance of the model is compared to four existing models for open water blasts, and for the severance of well conductors and piles. Simulated received underwater sound pressure levels were significantly correlated with measurements for all scenarios. The maximum total error achieved between simulations and measurements was 3.5%, suggesting that predictions are accurate to within 4% of the average measurement. A low relative bias was observed in the simulations when compared to measured values, suggesting only a small systematic underestimate (≤1% of average measurement) for most severance operations and a small overestimate (1.34%) for open water blasts.
... It is well understood that underwater anthropogenic sound can impact marine life (Hildebrand, 2005;Wright et al., 2007;Gomez et al., 2016). The exact effect will vary based on a multitude of factors (National Research Council, 2005) including but not limited to, characteristics inherent to the animal, the specific characteristics of the source of noise (Southall et al., 2007), the proximity of the animal to the source (Richardson et al., 1995;Erbe and Farmer, 2000;Falcone et al., 2017), whether the source and/or the animal is moving, and the behavioral state of the animal (Isojunno et al., 2016). ...
To add to the growing information about the effect of multibeam echosounder (MBES) operation on marine mammals, a study was conducted to assess the spatial foraging effort of Cuvier’s beaked whales during two MBES surveys conducted in January of 2017 and 2019 off of San Clemente Island, California. The MBES surveys took place on the Southern California Antisubmarine Warfare Range (SOAR), which contains an array of 89 hydrophones covering an area of approximately 1800 km ² over which foraging beaked whales were detected. A spatial autocorrelation analysis of foraging effort was conducted using the Moran’s I (global) and the Getis-Ord Gi ∗ (local) statistics, to understand the animals’ spatial use of the entire SOAR, as well as smaller areas, respectively, within the SOAR Before, During , and After the two MBES surveys. In both years, the global Moran’s I statistic suggested significant spatial clustering of foraging events on the SOAR during all analysis periods ( Before, During , and After ). In addition, a Kruskal-Wallis (comparison) test of both years revealed that the number of foraging events across analysis periods were similar within a given year. In 2017, the local Getis-Ord Gi ∗ analysis identified hot spots of foraging activity in the same general area of the SOAR during all analysis periods. This local result, in combination with the global and comparison results of 2017, suggest there was no obvious period-related change detected in foraging effort associated with the 2017 MBES survey at the resolution measurable with the hydrophone array. In 2019, the foraging hot spot area shifted from the southernmost corner of the SOAR Before , to the center During , and was split between the two locations After the MBES survey. Due to the pattern of period-related spatial change identified in 2019, and the lack of change detected in 2017, it was unclear whether the change detected in 2019 was a result of MBES activity or some other environmental factor. Nonetheless, the results strongly suggest that the level of detected foraging during either MBES survey did not change, and most of the foraging effort remained in the historically well-utilized foraging locations of Cuvier’s beaked whales on the SOAR.
... Codas are repeated stereotyped sequences of clicks lasting approximately 3 s with ICIs that are highly variable and groupspecific (Rendell and Whitehead, 2004;Gero et al., 2016;Oliveira et al., 2016). Regular clicks (0.5-1.2 s ICI) and creaks (0.01-0.1 s ICI) are associated with echolocation and foraging (Jaquet et al., 2001;Miller et al., 2004;Hildebrand, 2005;Watwood et al., 2006), while slow clicks are produced primarily by male sperm whales (>2 s ICI; Madsen et al., 2002;Oliveira et al., 2013). For the purposes of this study, a 15-min encounter was simulated for a whale producing regular clicks by generating 500 click times drawn from a standard uniform distribution on the interval (0 s, 900 s). ...
Passive acoustic monitoring using a towed line array of hydrophones is a standard method for localizing cetaceans during line-transect cetacean abundance surveys. Perpendicular distances estimated between localized whales and the trackline are essential for abundance estimation using acoustic data. Uncertainties in the acoustic data from hydrophone movement, sound propagation effects, errors in the time of arrival differences, and whale depth are not accounted for by most two-dimensional localization methods. Consequently, location and distance estimates for deep-diving cetaceans may be biased, creating uncertainty in abundance estimates. Here, a model-based localization approach is applied to towed line array acoustic data that incorporates sound propagation effects, accounts for sources of error, and localizes in three dimensions. The whale's true distance, ship trajectory, and whale movement greatly affected localization results in simulations. The localization method was applied to real acoustic data from two separate sperm whales, resulting in three-dimensional distance and depth estimates with position bounds for each whale. By incorporating sources of error, this three-dimensional model-based approach provides a method to address and integrate the inherent uncertainties in towed array acoustic data for more robust localization.
... The noise pollution has, in some areas, been raised to levels where it can be considered a threat to marine life and especially to marine mammals that rely heavily on sound for orientation and communication (Richardson et al., 1995;Southall et al., 2007;Moore et al., 2012a;Reeves et al., 2014;Simmonds et al., 2014;Williams et al., 2015;Graham et al., 2019). Several studies of the effects of noise on marine mammals have documented a broad range of negative effects, from masking of signals and avoidance behavior, to loss of hearing sensitivity, physical injury, cessation of feeding, and increased stress (Richardson et al., 1995;Hildebrand, 2005;Weilgart, 2007;Rolland et al., 2012;DeRuiter et al., 2013;Dunlop et al., 2018;Bröker, 2019). ...
One of the last pristine marine soundscapes, the Arctic, is exposed to increasing anthropogenic activities due to climate-induced decrease in sea ice coverage. In this study, we combined movement and behavioral data from animal-borne tags in a controlled sound exposure study to describe the reactions of narwhals, Monodon monoceros , to airgun pulses and ship noise. Sixteen narwhals were live captured and instrumented with satellite tags and Acousonde acoustic-behavioral recorders, and 11 of them were exposed to airgun pulses and vessel sounds. The sound exposure levels (SELs) of pulses from a small airgun (3.4 L) used in 2017 and a larger one (17.0 L) used in 2018 were measured using drifting recorders. The experiment was divided into trials with airgun and ship-noise exposure, intertrials with only ship-noise, and pre- and postexposure periods. Both trials and intertrials lasted ∼4 h on average per individual. Depending on the location of the whales, the number of separate exposures ranged between one and eight trials or intertrials. Received pulse SELs dropped below 130 dB re 1 μPa ² s by 2.5 km for the small airgun and 4–9 km for the larger airgun, and background noise levels were reached at distances of ∼3 and 8–10.5 km, respectively, for the small and big airguns. Avoidance reactions of the whales could be detected at distances >5 km in 2017 and >11 km in 2018 when in line of sight of the seismic vessel. Meanwhile, a ∼30% increase in horizontal travel speed could be detected up to 2 h before the seismic vessel was in line of sight. Applying line of sight as the criterion for exposure thus excludes some potential pre-response effects, and our estimates of effects must therefore be considered conservative. The whales reacted by changing their swimming speed and direction at distances between 5 and 24 km depending on topographical surroundings where the exposure occurred. The propensity of the whales to move towards the shore increased with increasing exposure (i.e., shorter distance to vessels) and was highest with the large airgun used in 2018, where the whales moved towards the shore at distances of 10–15 km. No long-term effects of the response study could be detected.
... Human impacts on the marine environment include, amongst others, the emission of sound in the form of shipping noise, dredging, oil-and gas exploration by seismic surveys, explosions in military activities and to remove ordnance, sonars, echo sounders, fish finders, harassment devices in aquaculture and gill net fisheries, pile-driving and vibro-piling for offshore installations, drilling and research . All of these noise sources contribute to an increase of underwater noise, which has been suggested to equal a tenfold rise in noise levels over the last decades (Hildebrand, 2004). Ship noise alone is suspected to have increased ambient ocean noise levels by 12 dB . ...
Harbour porpoises Phocoena phocoena in German waters are faced with a variety of different anthropogenic and natural stressors that can have serious effects on population development. Anthropogenic stressors include prey depletion, influences of chemical and pharmaceutical toxins, by-catch in static fishing gear, noise pollution and habitat degradation. Climate influences add to these stressors and may pose both natural as well as anthropogenic threats. Pile-driving noise for construction of offshore wind farms is a new influence that is suspected to have adverse effects on porpoises. Within German waters three subpopulations of porpoises can be found. The North Sea subpopulation extends into the Skagerrak and parts of the Kattegat, the Belt Sea subpopulations reaches from these regions into the waters of the Kiel and Mecklenburg Bight while the Baltic Proper subpopulation has its presumed boundaries at the Darß and Limhamn Sills and populates the waters of the inner Baltic Sea. While the abundance of porpoises in the North Sea seems stable, this has been questioned for the Belt Sea subpopulation. The Baltic Proper subpopulation is recognized as ‘critically endangered’ by the IUCN (International Union for Conservation of Nature) red list and surveys within the last decades have not lead to conclusive abundance estimates due to the scarcity of sightings. Within this study Stationary Acoustic Monitoring (SAM) with echolocation click loggers (T-PODs – Timing Porpoise Detectors and C-PODs – Cetacean PODs, both Chelonia Ltd., UK) was used to describe distribution patterns of porpoises and analyse factors driving acoustic presence of porpoises in German waters. Harbour porpoises use echolocation almost constantly and hence registrations on the loggers represent a relative measure for porpoise presence in an area. This relatively new method is still developing rapidly and neither analysis strategies nor devices are standardized as has been done for other assessment methods. However, when using these devices for monitoring, effect monitoring and other long-term studies, it is essential to standardize the instruments, as well as to develop standard procedures for data evaluation. To account for variability of the loggers, a rigorous calibration of the instruments was conducted prior to field trials and repeatedly over time. The results indicate that the older T-PODs (Chelonia Ltd., UK) had a wide variation in detection thresholds at the beginning of the study, but newer versions were found to be well standardized. For C-PODs (Chelonia Ltd., UK), the digital successor of the T-POD, the calibration showed a much better standardization at the preferred porpoise vocalisation frequency of 130 kHz. Other frequencies were less comparable indicating that surveys for species using lower frequencies must obtain calibration data for their instruments. The first long-term deployment of up to 42 T-PODs in the German Baltic Sea documented strong geographical and seasonal differences in porpoise occurrence. Instruments deployed closer together gathered more comparable data than devices further away. This indicates that these differences represent a genuine occurrence pattern with higher detection rates in westerly waters, which gradually decrease towards the Pomeranian Bay in the east. Overall, more porpoises were registered from spring to fall, indicating a possible relationship to herring as one preferred prey item. A second long-term study was conducted to analyse the echolocation behaviour of porpoises east of the Darß and south of the Limhamn Sill. Detection rates showed two peaks in seasonal occurrence of porpoises at these sites. This result indicates most likely that porpoises from both subpopulations in German waters use the area of the Pomeranian Bay in an alternating pattern of habitat use: porpoises from the Belt Sea distribute throughout German waters from spring to fall, with maximum detection rates in summer, while Baltic Proper porpoises use the area during winter to avoid suffocation in the closed ice cover in the inner Baltic waters. The modelling indicated that salinity was a significant factor for presumed Belt Sea animals, while temperature had significant influences on all detection rates. To estimate the impact of pile-driving noise on porpoises a third long-term study was conducted off the German coast close to Borkum Reefground, where the first German offshore wind farm alpha ventus was constructed from 2008 to 2009. Visual observations showed a strong displacement of porpoises during pile-driving out to a distance of ~20 km around the pile-driving site during a survey exactly timed to the piling activities. Acoustic monitoring showed reduced detection rates close to the pile-driving operation in distances up to 11 km. There were no stations between 11 and 23 km distance. At 25 and 50 km distance detection rates increased indicating that porpoises were possibly displaced towards these positions and hence a behavioural reaction was recorded outside of the displacement radius. Furthermore, the duration of porpoise absence during and after pile-driving was correlated with the duration of pile-driving. From this data it remained unclear whether the displacement process was fully completed. To mitigate effects, such as described for the construction of alpha ventus, more work is necessary to find suitable noise mitigation measures. In a previous project it was shown that a stacked bubble curtain greatly reduced the sound levels, as well as the behavioural reaction in captive porpoises during harbour construction work in Denmark. In a follow up project it was tested which factors actually led to the large attenuation and how different nozzle layouts in a test tank environment under controlled conditions lead to changed attenuation rates. A second test of a single system was carried out in Kiel harbour. For both of these trials an underwater loudspeaker served as the sound source and modulated sine wave impulses were used to test attenuation efficacy. The resulting attenuation rates were much larger than previously reported. This is most probably linked to the sound source that was used in these experiments, which does not behave like a pile being driven. The pile is a line source with contact to three media: air, water and sediment. We tested only the water transmission path in these experiments. However, transmission through the sediment may play a large role in offshore conditions and must be accounted for within future offshore construction work.
... Ulteriori studi sono necessari per indagare e valutare le complessità di queste interazioni distinguendo tra effetti cumulativi, moltiplicativi e sinergici. Per di più, lo studio degli effetti a livello della popolazione è complicato, anche perché le osservazioni devono essere condotte su grandi distanze e per lunghi periodi di tempo, rendendo molto difficile la correlazione causa-effetto (Hildebrand, 2005). ...
... These reviews highlight that underwater noise from human activities can impact individuals and populations of marine organisms in complex ways. Impacts have been observed on all trophic levels, from invertebrates to fish, marine mammals, and diving seabirds [3,[5][6][7][28][29][30]. Whereas in marine mammals and seabirds, hearing and noise impacts depend on detection of the pressure component of sound [29,31], many marine fish and invertebrates primarily sense and are impacted by noise through particle motion [32]. ...
... Active acoustic sensing is sensing of mammal sounds using sonar (echoes) where the cetaceans need not produce any sound. In addition to noise generated by marine species, anthropogenic noise, and ambient noise also contribute immensely to the noise produced in the oceans [5]. Depending on the intensity of sound generated at the source level, pitch, and the range of distance between the source and the receiver, the sound produced affects marine species in countless ways [6]. ...
In recent years, oceanic based research is gradually growing across the globe. Most researchers in this field aim at resolving the major challenges of Underwater Acoustic Sensor Networks like limited band-width, high propagation delay, 3D topology, media access control, routing, resource utilization, and power constraint neglecting spectrum utilization. However, most UAN designs consider the acoustic communication in underwater as a single network and only a very few consider the existence of other multiple acoustic systems in the ocean. Both the natural acoustic systems and artificial acoustic systems in the ocean use the acoustic means of communication leading to a heavily overcrowded spectrum. Despite the oversharing of channels the spectrum is still temporally and spatially underutilized. Unlike cognitive radio, spectrum allocation in cognitive acoustics is highly challenging due to the unique features of the underwater channel and the acoustic systems. The increasing intervention of anthropogenic activities in the oceans has resulted in an overshared, scarce, and inefficiently utilized spectrum. As an effort to calm down these adverse impacts, an underwater cognitive acoustic network-based spectrum decision strategy is proposed in this paper to aid in efficient spectrum utilization and allocation by multiple acoustic systems in the underwater environment. The proposed strategy is aimed at an environmentally friendly spectrum utilization model with much emphasis given to the primary users, the marine species. This paper considers all possible marine species and not just limit it to marine mammals. Finally, the scope of this paper is to provide an in-depth view of cognitive acoustics in UASN that can pay way for environmentally safe underwater research and marine habitat conservation in the future.
... No entanto, devido às características geomorfológicas, estes ambientes costeiros protegidos também abrigam portos, estaleiros e marinas, os quais são fontes de estressores ambientais (Bittencourt et al., 2017;Cremer et al., 2009;Silva et al., 2015). As atividades náuticas relacionadas a estas estruturas geram alterações físicas ao ambiente, e a dependência de condições seguras à navegação demandam ações de dragagem e derrocagem (Hildebrand, 2005). ...
Resumo: Obras de derrocagem são executadas para garantir navegabilidade em áreas portuárias, entretanto geram impactos ao ambiente e à fauna marinha. Estas obras ocorrem em áreas com atividades antropogênicas e somam efeitos aos múltiplos estressores ecossistêmicos. Efeitos cumulativos causam desde a degradação ambiental até efeitos individuais e populacionais à fauna. Diversas espécies costeiras de golfinhos estão ameaçadas de extinção e são vulneráveis a esses impactos. Entre as espécies que ocorrem no Brasil, populações de boto-cinza (Sotalia guianensis) na região sudeste e sul são de extrema preocupação em relação a impactos portuários e derrocagens, assim como outras espécies de golfinhos costeiros. Para botos-cinza, há registro de alterações sociais e de uso de área, além de imunossupressão relacionadas a exposição à estressores em áreas portuárias. Considerando estas informações, propomos que licenciamentos de obras de derrocagem abordem métodos com diretrizes que visem à prevenção e mitigação de impactos aos cetáceos. Visando auxiliar tecnicamente o processo de avaliação e monitoramento no âmbito do licenciamento ambiental, este artigo apresenta uma revisão sistemática da literatura científica quanto aos principais impactos em golfinhos causados por explosões subaquáticas vinculadas a derrocagem e métodos de avaliação e redução de danos. Os resultados obtidos destacam efeitos que incluem injúrias físicas; alterações comportamentais como abandono de área e afugentamento; e alterações na comunicação social por mascaramento sonoro ou perdas auditivas temporárias/permanentes. Ainda, foram levantados e avaliados métodos para elaboração de programas ambientais destas atividades, seguido por sugestões de procedimentos a serem aplicados para redução de impactos. Palavras-Chave: Boto-cinza; Degradação ambiental; Explosões subaquáticas; Impactos cumulativos; Licenciamento ambiental. Abstract: Underwater explosion and potential impacts on costal dolphins: evaluation, monitoring and mitigation actions. Underwater explosions are carried out to ensure navigability in port areas; however, they generate many impacts on the marine environment and fauna. Underwater blasting often occurs in areas with many anthropogenic activities, consequently bringing together multiple ecosystem stressors. Cumulative impacts can range from degradation of the ecosystem as a whole, to impacts on both population and individual level. Several endangered coastal dolphin species are exposed to these impacts, such as the populations of Guiana dolphins (Sotalia guianensis) in southeastern and southern Brazil, which are vulnerable to port impacts and underwater explosions. This species has been observed to change its social behavior and habitat use patterns and has even presented immunosuppression due to the exposure to port stressors. In order to avoid and mitigate these impacts, the licensing for underwater explosions must be built upon efficient environmental management guidelines. This study presents a systematic literature review to identify the main impacts of underwater explosions on small coastal cetaceans, supporting the assessment and monitoring of the environmental licensing process. Results highlighted effects that included physical injuries, such as damage to auditory and gas-filled organs; behavioral disturbances, such as avoidance and displacement; and disruption of social communication, caused by acoustic masking and temporary or permanent hearing loss. In this light, methods for environmental licensing programs were evaluated and possible impact reducing procedures are presented. This broad overview provides crucial perspectives on how underwater explosions are impacting small coastal cetaceans, and how these impacts can be reduced through the environmental licensing process.
... Additionally, there has been little dedicated study of American Crocodile bioacoustics anywhere in its range. Increasingly, anthropogenic noise and impact in wildlife habitat is demonstrated to have deleterious effects on wildlife acoustics and ecology (Blickley & Patricelli, 2010;Hildebrand, 2005;Laiolo, 2010). As an acoustically communicative species, it is feasible that American Crocodile sound production may be affected by anthropogenic disturbance. ...
Acoustic communication of American Crocodiles (Crocodylus acutus) is relatively understudied. Our overall aim was to determine the acoustic structure of wild American Crocodile distress calls, distinguish call differences among size classes (hatchling, juvenile, sub‐adult, and adult), and investigate call production on a gradient of human disturbance. American Crocodile distress calls have strong frequency modulation and are comprised of multiple harmonics in a downsweeping pattern. Measured parameters (total duration, first quartile duration, maximal frequency, first quartile frequency, end frequency, slope of first quartile, slope of last quartiles) differed significantly among size classes (p < .05). Hatchling distress calls are higher in frequency and strongly modulated, whereas calls produced by sub‐adults and adults showed little modulation, are lower in frequency, and have greater overall duration. Proportion of crocodiles that produced distress calls during capture differed by size class and sampling location, particularly adult distress calls which are reported here to be produced with undocumented frequency. We determined that American Crocodiles of all size classes produce distress calls at varying rates among study sites. Our results demonstrate that American crocodiles produce distress call more frequently at sites with higher anthropogenic activity. Measured call parameters of juveniles and hatchling American crocodiles also varied among sites in relation to human disturbance. Calls recorded at sites of high anthropogenic impact have increased duration and less modulation which may adversely affect response to emitted distress calls. Proportional and call parameter variances suggest anthropogenic activity as a driver for increased call production and alteration of call parameters at high human‐impacted sites.
... Considering the worldwide shipping traffic, URN is known to affect the survivability of marine mammals by masking frequency bands used for their fundamental living activities. [1][2][3] Ships URN can be classified into two categories according to their sources, machinery noise and flow-induced noise generated by the propeller rotation. Machinery noise is not strictly affected by the ship speed and can be shielded by sound absorbing materials and vibration control. ...
The application of artificial roughness to mitigate tip vortex cavitation inception is analyzed through numerical and experimental investigations carried out on an elliptical foil. Different roughness configurations and sizes are tested, and effects on cavitation inception, drag, and lift are studied. Implicit Large Eddy Simulation is employed to conduct the simulation on a proper grid resolution having the tip vortex spatial resolution as fine as 0.062 mm. Two different approaches including using a rough wall function and resolving the flow around roughness elements are evaluated. New experiments, performed in the cavitation tunnel at Kongsberg Hydrodynamic Research Center, for the rough foil are presented. The vortical structures and vorticity magnitude distributions are employed to demonstrate how different roughness patterns and configurations contribute to the vortex roll-up and consequently on the tip vortex strength. It is found that the application of roughness on the leading edge, tip region, and trailing edge of the suction side is acceptable to mitigate the tip vortex and also to limit the performance degradation. This is regarded to be in close relation with the way that the tip vortex forms in the studied operating condition. The boundary layer characteristics show that roughness separation line is the reason for a more even distribution of vorticity over the tip compared to the smooth foil condition, leading to a reduction in vortex strength. For the optimum roughness pattern, both the numerical results and experimental measurements show a decrease in the tip vortex cavitation inception as large as 33% compared to the smooth foil condition with a drag force increase observed to be less than 2%.
... Considering the worldwide shipping traffic, URN is known to affect the survivability of marine mammals by masking frequency bands used for their fundamental living activities. [1][2][3] Ships URN can be classified into two categories according to their sources, machinery noise and flow-induced noise generated by the propeller rotation. Machinery noise is not strictly affected by the ship speed and can be shielded by sound absorbing materials and vibration control. ...
The application of artificial roughness to mitigate tip vortex cavitation inception is analyzed through numerical and experimental investigations carried out on an elliptical foil. Different roughness configurations and sizes are tested, and effects on cavitation inception, drag, and lift are studied. Implicit Large Eddy Simulation is employed to conduct the simulation on a proper grid resolution having the tip vortex spatial resolution as fine as 0.062 mm. Two different approaches including using a rough wall function and resolving the flow around roughness elements are evaluated. New experiments, performed in the cavitation tunnel at Kongsberg Hydrodynamic Research Center, for the rough foil are presented. The vortical structures and vorticity magnitude distributions are employed to demonstrate how different roughness patterns and configurations contribute to the vortex roll-up and consequently on the tip vortex strength. It is found that the application of roughness on the leading edge, tip region, and trailing edge of the suction side is acceptable to mitigate the tip vortex and also to limit the performance degradation. This is regarded to be in close relation with the way that the tip vortex forms in the studied operating condition. The boundary layer characteristics show that roughness separation line is the reason for a more even distribution of vorticity over the tip compared to the smooth foil condition, leading to a reduction in vortex strength. For the optimum roughness pattern, both the numerical results and experimental measurements show a decrease in the tip vortex cavitation inception as large as 33% compared to the smooth foil condition with a drag force increase observed to be less than 2%.
... Many sources of noise are located along with travelled paths in the sea, particularly in coastal and continental shelf waters, areas that often include important marine mammal habitats. Considering the worldwide shipping traffic, URN are known to affect the survivability of marine mammals by masking frequency bands used for their fundamental living activities [1][2][3]. ...
The application of artificial roughness to mitigate tip vortex cavitation inception is analyzed through numerical and experimental investigations carried out on an elliptical foil. Different roughness configurations and sizes are tested, and effects on cavitation inception, drag, and lift are studied. Implicit Large Eddy Simulation is employed to conduct the simulation on a proper grid resolution having the tip vortex spatial resolution as fine as 0.062 mm. Two different approaches including using a rough wall function and resolving the flow around roughness elements are evaluated. New experiments, performed in the cavitation tunnel at Kongsberg Hydrodynamic Research Center, for the rough foil are presented. The vortical structures and vorticity magnitude distributions are employed to demonstrate how different roughness patterns and configurations contribute to the vortex roll-up and consequently on the tip vortex strength. It is found that the application of roughness on the leading edge, tip region, and trailing edge of the suction side is acceptable to mitigate the tip vortex and also to limit the performance degradation. This is regarded to be in close relation with the way that the tip vortex forms in the studied operating condition. The boundary layer characteristics show that roughness separation line is the reason for a more even distribution of vorticity over the tip compared to the smooth foil condition, leading to a reduction in vortex strength. For the optimum roughness pattern, both the numerical results and experimental measurements show a decrease in the tip vortex cavitation inception as large as 33% compared to the smooth foil condition with a drag force increase observed to be less than 2%.
... Furthermore, it is ironic that a further potential threat to whales and hence to whale-watching activities is the noise caused by marine vessels. These are a major contributor to anthropogenic noise in the ocean (Hildebrand, 2005). It seems clear that this has deleterious behavioural, physiological, and acoustic effects on many cetaceans (Nowacek et al., 2007), including the blue whale (Goldbogen et al., 2013). ...
What are the challenges and opportunities for future regional development in the Nordic Region? And how can the Nordic Cooperation Programme on Regional Policy be relevant in responding to this question? This was the focus of a seminar held in Akureyri in 2019 where six invited authors as well as discussants selected amongst the members of the Committee of Senior Officials for Regional Policy and Nordregio’s Board of Directors presented their views on these questions. This working papers containts the presentations of the seminar.
... There is growing concern that seismic surveys may have adverse impacts on marine life, ranging from physiological to behavioral impacts. Broadly, these include disruption of communication ( Cerchio et al. 2014, Dahlheim & Castellote 2016, temporary displacement from habitat ( Yazvenko et al. 2007, Castellote et al. 2012), and potential mortality ( Gordon et al. 2003, Hildebrand 2005). Of particular concern are the effects of chronic noise on animals, such as stress ( Nowacek et al. 2007, Tyack 2008, Rolland et al. 2012) and hearing damage, especially from accumulated exposure (Weilgart 2007). ...
Anthropogenic noise is increasing throughout the world’s oceans. One major contributor is industrial seismic surveys—a process typically undertaken to locate and estimate the quantity of oil and gas deposits beneath the seafloor—which, in recent years, has increased in magnitude and scope in some regions. Regulators permit this activity despite widespread uncertainties regarding the potential ecological impacts of seismic surveys and gaps in baseline information on some key species of conservation concern. Research to date suggests that impacts vary, from displacement to direct mortality, but these effects remain poorly understood for most species. Here, we summarize potential effects of seismic surveys, describe key knowledge gaps, and recommend broad-scale research priorities for 3 impacted taxonomic groups: fish, marine mammals, and sea turtles. We also suggest further technological advances, improved mitigation measures, and better policy and management structures to minimize the ecological impacts of seismic surveys in light of scientific uncertainty.
... Furthermore, it is ironic that a further potential threat to whales and hence to whale-watching activities is the noise caused by marine vessels. These are a major contributor to anthropogenic noise in the ocean (Hildebrand, 2005). It seems clear that this has deleterious behavioural, physiological, and acoustic effects on many cetaceans (Nowacek et al., 2007), including the blue whale (Goldbogen et al., 2013). ...
... Growing industrialization of the marine environment is resulting in habitat changes and increasing marine defaunation (McCauley et al., 2015;Richardson, Greene, Malme, & Thomson, 1995). A greater awareness of increasing levels of anthropogenic noise has prompted studies to understand and mitigate their potential negative impacts on marine life (Hildebrand, 2005). While many recent studies have sought to address the effects of underwater noise on cetaceans (Nowacek, Thorne, Johnston, & Tyack, 2007), comparatively less is known about exposure and reactions to noise in pinnipeds while at sea. ...
• The impact of anthropogenic noise on marine fauna is of increasing conservation concern with vessel noise being one of the major contributors. Animals that rely on shallow coastal habitats may be especially vulnerable to this form of pollution.
• Very limited information is available on how much noise from ship traffic individual animals experience, and how they may react to it due to a lack of suitable methods. To address this, we developed long‐duration audio and 3D‐movement tags (DTAGs) and deployed them on three harbor seals and two gray seals in the North Sea during 2015–2016.
• These tags recorded sound, accelerometry, magnetometry, and pressure continuously for up to 21 days. GPS positions were also sampled for one seal continuously throughout the recording period. A separate tag, combining a camera and an accelerometer logger, was deployed on two harbor seals to visualize specific behaviors that helped interpret accelerometer signals in the DTAG data.
• Combining data from depth, accelerometer, and audio sensors, we found that animals spent 6.6%–42.3% of the time hauled out (either on land or partly submerged), and 5.3%–12.4% of their at‐sea time resting at the sea bottom, while the remaining time was used for traveling, resting at surface, and foraging. Animals were exposed to audible vessel noise 2.2%–20.5% of their time when in water, and we demonstrate that interruption of functional behaviors (e.g., resting) in some cases coincides with high‐level vessel noise. Two‐thirds of the ship noise events were traceable by the AIS vessel tracking system, while one‐third comprised vessels without AIS.
• This preliminary study demonstrates how concomitant long‐term continuous broadband on‐animal sound and movement recordings may be an important tool in future quantification of disturbance effects of anthropogenic activities at sea and assessment of long‐term population impacts on pinnipeds.
... There is mounting concern about the impact of seismic surveys on marine life (Gordon et al., 2003;Hildebrand, 2005;Southall et al., 2008;Weilgart, 2013;Nowacek et al., 2015;Williams et al., 2015;McCauley et al., 2017). Marine life, with the exception of whales that communicate with low frequency (15-100 Hz) calls (Goldbogen et al., 2014;Stimpert et al., 2015;Watson et al., 2017b), is thought to be most sensitive to the nongeophysically useful high-frequency component of air-gun signals (Kastelein et al., 2014;Finneran, 2015). ...
Seismic air guns are broadband sources that generate acoustic waves at many frequencies. The low-frequency waves can be used for imaging, whereas the high-frequency waves are attenuated and/or scattered before they can reflect from targets of interest in the subsurface. It is desirable to reduce the amplitude of the high-frequency acoustic waves because they are thought to be disruptive, and potentially damaging, to marine life and are not useful for geophysical purposes. The high-frequency acoustic waves are primarily associated with the initial expansion of the air-gun bubble and associated peak in the acoustic pressure time series, which is commonly referred to as the source signature of the air gun. We have developed a quasi-1D model of a seismic air gun coupled to a spherical bubble that accounts for gas dynamics and spatially variable depressurization inside the firing chamber to investigate controls on the initial peak of the source signature. The model is validated against data collected during field tests in Lake Seneca, New York. Simulations and field data show that the initial peak is primarily dependent on the operating pressure. A lower gun pressure results in a smaller peak amplitude and a slower rise time. The slope, the amplitude of the initial peak divided by the rise time, is used as a proxy for environmental impact and can decrease by as much as 50% when the air-gun pressure is reduced from 2000 to 1000 psi. The low frequencies are controlled by the total discharged mass, which is dependent upon the gun volume and pressure. Decreasing the operating pressure while simultaneously increasing the gun volume will reduce the high frequencies while maintaining the desirable low-frequency signals.
... Man-made conventional underwater actuators like thrusters are noisy which make them unfit for stealth operations and can potentially disturb the surrounding aquatic environment. The noise of the thrusters can cause interference in the communication between different aquatic species and may also cause trauma [1,2]. Biomimetic propulsive devices are thought to be better alternative to solve some aforementioned problems. ...
... The consequences of this trend experienced by the world fleet have been observed to impact the lowfrequency ambient noise levels as it is the dominant noise source in this frequency region, as identified by Wenz [3]. Namely, the measurements made in the Pacific Ocean indicate a 3-dB increase per decade (or 10 dB per half century) in terms of measured background noise levels, as summarized in Fig. 1 by Frisk, based on the compiled historical ambient noise data [4]- [6]. ...
Conducting noise trials with big merchant vessels could constitute serious economic and time losses for the ship operators. This study aims to introduce an experimental acoustic–visual device enabling economical and cost-effective noise trials in full scale. Noise emission and dynamics of propeller cavitation are investigated on a research vessel equipped with a customized submerged device called “Hydropod” that consists of hydrophones and a high definition, wide-angle underwater camera. Previously conducted noise trials following the international standards with an off-board hydrophone array are utilized for the validation of the adopted approach. The comparisons between the Hydropod measurements and conventional noise trial measurement results have shown promising correlations, except for a self-noise hump present in the noise spectra of the Hydropod measurements. Furthermore, by taking advantage of the replacement of the conventional propellers of the catamaran with a set of new profile technology (NPT) propellers, additional trials were conducted using the Hydropod. This enabled interpretation of the relative performance of both sets of propellers in terms of acoustics and cavitation extent. The NPT propellers were superior compared to the conventional propellers over the cavitation extent and resulting acoustic emissions.
... Understanding spatial and temporal fluctuations in behaviour is necessary to understand how a population uses its environment, and in turn how to effectively manage it (Stockin, Binedell, Wiseman, Brunton, & Orams, 2009). As reported in several studies, the dynamics of cohesion or dispersal influencing grouping patterns in dolphin species is mainly shaped by food availability (Benoit-Bird & Au, 2009;Heithaus & Dill, 2002;Karczmarski, Würsig, Gailey, Larson, & Vanderlip, 2005;Miyazaki, Kasuya, & Nishiwaki, 1973;Pearson, 2009), predation risks or human disturbances (Dolman, Evans, Notarbartolo di Sciara, & Frisch, 2010;Fossi & Lauriano, 2008;Gowans, Würsig, & Karczmarski, 2008;Hildebrand, 2005), intra-sexual competition and inter-sexual conflicts (Clutton-Brock, 2007), as well as habitat heterogeneity (Azzellino, Airoldi, Gaspari, & Nani, 2008;Tyne, Johnston, Rankin, Loneragan, & Bejder, 2015). Concerning the geomorphological complexity, the hydrographic characteristics and the anthropogenic disturbances in the northern Ionian Sea seem to drive not only the habitat suitability for the striped dolphin (Carlucci et al., 2016), but also its daily variations in group size through changes in aggregation patterns, depths and activity states. ...
Abundance, density, daily variation in group size, activity and habitat use of the striped dolphin in the Gulf of Taranto (northern Ionian Sea, central Mediterranean Sea) were investigated using data from sightings collected between April 2009 and December 2016 during standardized vessel-based surveys. Density and abundance were estimated in the survey area by means of conventional distance sampling, resulting in 0.97 specimens/km² (CV = 5.77%; 95% CI = 0.86-1.08 specimens/km²) and 615 specimens (CV = 5.77%; 95% CI = 549-689 specimens), respectively. Group size data were analysed using multivariate methods. The changes in group size, depth and percentage occurrence of activity between daily periods were investigated with non-parametric tests. The spatio-temporal distribution of the striped dolphin in each predominant activity was investigated by means of the ordinary Kriging method. Fifteen year-maps of spatial prediction were produced, allowing the identification of persistent areas. The results delineate a critical habitat of about 150 km² in the northernmost 'Taranto Valley' canyon system ranging between 140 and 910 m in depth. This critical habitat was persistently and regularly used by an important estimated population of striped dolphins for their day-to-day survival and maintenance in a healthy condition. The intense human use occurring in the area highlights the need for local, national and EU management to set a comprehensive strategy. The establishment of a SPAMI (Specially Protected Area of Mediterranean Importance) as an effective tool for the conservation of the species is suggested. The consequence of establishing a closed area could be reasonably accepted by local concurrent stakeholders. Indeed, limiting access through the establishment of this small closed area would result in the protection of a habitat acting as an ecological refuge for many other pelagic and demersal species of commercial interest, thus favouring their spill over.
... There is significant concern about the impact of anthropogenic noise, a substantial amount of which is due to seismic surveys (Hildebrand, 2005), on marine life. Several studies have documented behavioral changes and temporary or permanent threshold shifts in the hearing of marine mammals as a result of exposure to seismic surveys (e.g., Gordon et al., 2003;Weilgart, 2013). ...
Este artículo aborda la cuestión de la protección que diversas normas, nacionales e internacionales, dispensan a los animales marinos frente a la contaminación acústica de origen antropogénico. Se analiza, en particular, el régimen jurídico tuitivo de los cetáceos frente al ruido producido por los sónares de los buques de guerra.
The potential impact of underwater radiated noise from maritime operations on marine fauna has become an important issue. The most dominant noise source on a propeller-driven vessel is propeller cavitation, producing both structure-borne and radiated noise, with a broad spectrum that covers a wide range of frequencies. To ensure acceptable noise levels for sustainable shipping, accurate prediction of the noise signature is essential, and procedures able to provide a reliable estimate of propeller cavitation noise are becoming a fundamental tool of the design process. In this work, we investigate the potential of using computationally cheap methods for the prediction of underwater radiated noise from cavitating marine propellers. We compare computational and experimental results on a subset of the Meridian standard propeller series, behind different severities of axial wake, for a total of 432 experiments. The results indicate that the approaches employed can be a convenient solution for noise analysis during the design process.
First book dedicated to Biodiversity Beyond National Jurisdiction gathering a diverse crowd of authors from various backgrounds and professions. This book was conceived as a guide book for delegations before the start of the negotiations. It highlights many issues including governance, sustainable management, conservation on the seabed, conservation in the water column, marine pollution, sustainable use of biodiversity and marine genetic resources , polar zones, benefit sharing & dispute settlements.
The description of underwater soundscape is central to the understanding of the marine environment, both from the standpoint of the fauna and anthropic activities and its interactions with the atmosphere. Some of these sources produce signals whose patterns are periodically repeated over time (i.e., ship propellers in motion, odontocetes clicks, snapping shrimp, noise emanating from surface waves, etc.). As ocean noise is a combination of various sources sometimes sharing the same frequency band, it is necessary to develop efficient algorithms to process the increasingly voluminous data acquired. To this end, the theory of cyclostationarity is adopted as an effective tool for exposing hidden periodicities in low signal to noise ratio. This theory, widely used to analyze mechanical systems or communications, is extended and applied on underwater soundscapes. The method is demonstrated using data recorded in the Celtic Sea at the French coast of Brittany with practical experiments using field measurements obtained from recording stations.
In recent years, oceanic based research is gradually growing across the globe. Most researchers in this field aim at resolving the major challenges of Underwater Acoustic Sensor Networks like limited bandwidth, high propagation delay, 3D topology, media access control, routing, resource utilization, and power constraint neglecting spectrum utilization. However, most UAN designs consider the acoustic communication in underwater as a single network and only a very few consider the existence of other multiple acoustic systems in the ocean. Both the natural acoustic systems and artificial acoustic systems in the ocean use the acoustic means of communication leading to a heavily overcrowded spectrum. Despite the oversharing of channels the spectrum is still temporally and spatially underutilized. Unlike cognitive radio, spectrum allocation in cognitive acoustics is highly challenging due to the unique features of the underwater channel and the acoustic systems. The increasing intervention of anthropogenic activities in the oceans has resulted in an overshared, scarce, and inefficiently utilized spectrum. As an effort to calm down these adverse impacts, an underwater cognitive acoustic network-based spectrum decision strategy is proposed in this paper to aid in efficient spectrum utilization and allocation by multiple acoustic systems in the underwater environment. The proposed strategy is aimed at an environmentally friendly spectrum utilization model with much emphasis given to the primary users, the marine species. This paper considers all possible marine species and not just limit it to marine mammals. Finally, the scope of this paper is to provide an in-depth view of cognitive acoustics in UASN that can pay way for environmentally safe underwater research and marine habitat conservation in the future.
Coastal zones have large social, economic and environmental values. They are more densely populated than the hinterland and concentrate large economic assets, critical infrastructures and human activities such as tourism, fisheries, navigation. Furthermore, coastal oceans are home to a wealth of living marine resources and very productive ecosystems. Yet, coastal zones are exposed to various natural and anthropogenic hazards. To reduce the risks associated with marine hazards, sustained coastal zone monitoring programs, forecasting and early warning systems are increasingly needed. Earth observations (EO), and in particular satellite remote sensing, provide invaluable information: satellite-borne sensors allow an effective monitoring of the quasi-global ocean, with synoptic views of large areas, good spatial and temporal resolution, and sustained time-series covering several years to decades. However, satellite observations do not always meet the precision required by users, in particular in dynamic coastal zones, characterized by shorter-scale variability. A variety of sensors are used to directly monitor the coastal zone and their observations can also be integrated into numerical models to provide a full 4D monitoring of the ocean and forecasts. Here, we review how EO, and more particularly satellite observations, can monitor coastal hazards and their drivers. These include coastal flooding, shoreline changes, maritime security, marine pollution, water quality, and marine ecology shifts on the one hand, and several physical characteristics (bathymetry, topography, vertical land motion) of coastal zones, meteorological and oceanic (metocean) variables that can act as forcing factors for coastal hazards on the other hand.
The risks military sonar poses to cetaceans received international attention with a highly-publicized mass stranding of Cuvier's beaked whales (Ziphius cavirostris), Blainville's beaked whales (Mesoplodon densirostris), and northern minke whales (Balaenoptera acutorostrata) in the Bahamas in 2000. This was the first time that the US Government determined a stranding to be the result of mid-frequency active sonar use. Subsequently attention has been drawn to other mass strandings coincident with naval exercises, including events preceding the 2000 mass stranding. The list of species for which mass strandings have been linked to naval exercises has also increased to include other beaked whales, dwarf and pygmy sperm whales (Kogia spp.), pilot whales (Globicephala spp.), several dolphin species (Stenella sp. and Delphinus delphis), and harbor porpoises (Phocoena phocoena). In particular, there have been several mass strandings in the northern Indian Ocean coincident with naval exercises—including one of the largest (200–250 dolphins)—which have received little attention. Changes in beaked whale behavior, including evasive maneuvering, have been recorded at received levels below <100 dB re 1 μPa (rms) and mass stranding may occur at received levels potentially as low as 150–170 dB re 1 μPa. There is strong scientific evidence to suggest that a wide range of whale, dolphin and porpoise species can also be impacted by sound produced during military activities, with significant effects occurring at received levels lower than previously predicted. Although there are many stranding events that have occurred coincident with the presence of naval vessels or exercises, it is important to emphasize that even the absence of strandings in a region does not equate to an absence of deaths, i.e., absence of evidence does not mean evidence of absence. Strandings may be undetected, or be unlikely to be observed because of a lack of search effort or due to coastal topography or characteristics. There may also be “hidden” impacts of sonar and exercises not readily observable (e.g., stress responses). Due to the level of uncertainty related to this issue, ongoing baseline monitoring for cetaceans in exercise areas is important and managers should take a precautionary approach to mitigating impacts and protecting species.
Data on bycatch of harbour porpoise (Phocoena phocoena L.) in the commercial Danish set-net fisheries were sampled from 5,591km nets in the period 1992 to 1998 using independent observers. A total bycatch of 325 harbour porpoises was reported. Cluster analysis was used to stratify the sampled fishing trips and official catch statistics into a number of different m6tiers defined by the target species for the trips. Extrapolation of the observed bycatch rate to total fish landings of the Danish set-net fleet gave an average annual bycatch of 6,785 (CV 0.12) for the North Sea fisheries in the period 1994-1998. Sampling was not sufficient to estimate total bycatch for other areas. Bycatch was observed in Kattegat but not in the Baltic Sea. Generalised Linear Models were used to identify significant factors for bycatch in the North Sea. The bycatch rate, given as number per length of nets x soak time, was significantly lower in fisheries for flatfish compared to roundfish fisheries. The highest bycatch rate was in the cod fishery over wrecks and no bycatch was observed in the sole fishery. Significant seasonal variation of bycatch was identified with the highest bycatch rate in the first and third quarter of the year. Bycatch rates had not changed in the observed period and there was no significant difference in bycatch rates between sub-areas.
Small cetaceans are susceptible to incidental mortality in the various forms of gillnet fisheries throughout their range. Research conducted since 1994 has shown that acoustic alarms (pingers) emitting high-frequency pulsed sounds effectively reduce the number of harbor porpoise Phocoena phocoena casualties in sink gillnets. However, the mechanisms behind the effects of pingers were still not understood. Until now, advantages and risks associated with their widespread use could not be evaluated. Here we present the results of 2 field experiments: (1) theodolite-tracking of harbor porpoises exposed to a single PICE-pinger in Clayoquot Sound, Vancouver Island, Canada and (2) herring Clupea harengus capture rates in surface gillnets equipped with and without acoustic alarms (Dukane Netmark 1000, Lien, PICE) in the Baltic Sea herring fishery at Rugen Island, Germany. Our results show that harbor porpoises do not seem to react to an experimental net in their foraging area (n = 172 groups, median group size = 2 porpoises). Porpoise distance from the mid-point of the net was distributed around a median of only 150 m (range 4 to 987 m). A net equipped with an acoustic alarm, however, was avoided (n = 44 groups) within audible range (distance distribution median = 530 m, range 130 to 1140 m). The porpoises were thus effectively excluded from the ensonified area. Herring, one of the main prey species of harbor porpoises, were not affected by the acoustic alarms tested (n = 25 407 fish captured). The advantages and risks of using acoustic alarms to mitigate by-catch are discussed.
Humpback whale (Megaptera novaeangliae) entrapment in nets is a common phenomenon in Newfoundland. In 1991-1992, unusually high entrapment rates were recorded in Trinity Bay on the northeast coast of Newfoundland. The majority of cases occurred in the southern portion of the bay close to Mosquito Cove, a site associated with construction operations (including explosions and drilling) that presumably modified the underwater acoustic environment of lower Trinity Bay. This study reports the findings of the resulting assessment conducted in June 1992 on the impact of the industrial activity on humpback whales foraging in the area. Although explosions were characterized by high-energy signatures with principal energies under 1 kHz, humpback whales showed little behavioral reaction to the detonations in terms of decreased residency, overall movements, or general behavior. However, it appears that the increased entrapment rate may have been influenced by the long-term effects of exposure to deleterious levels of sound.
Large bycatches of harbour porpoises (Phocoena phocoena) occur in gillnet fisheries throughout the Northern Hemisphere. Several mitigation measures, including acoustic deterrent devices or 'pingers', have been used in efforts to reduce this bycatch. The potential exists for harbour porpoises to habituate to pingers, thus reducing their effectiveness over time. A field experiment was conducted to test the hypothesis that porpoises habituate to the sound produced by pingers. Porpoise echolocation and movements were monitored around a mooring equipped with a pinger (Dukane NetMark™ 1000) for three months in summer 1998 in the Bay of Fundy. Using a mean-shift model it was estimated that porpoises were initially displaced 208m from the pinger (p = 0.019), but this displacement diminished by 50% within four days (p = 0.019). Using a probability model it was demonstrated that the probability of porpoises within 125m of the pinger initially decreased when the pinger was turned on, but then increased to equal the control in 10-11 days. Echolocation rate (p < 0.001) and occurrence (p < 0.001) were significantly reduced in the vicinity of the pinger. These results indicate that porpoises habituated to the Dukane NetMark™ 1000 pinger and are not alerted to echolocate in the presence of nets by pingers.
Female sea otters (Enhydra lutris) with young observed along the coast from Point Lobos State Park to Lucia, California, spent 8 per cent of their daylight hours nursing their young, 20 per cent grooming their young, 10 per cent grooming themselves, 16 per cent feeding, 13 per cent swimming and 41 per cent resting. Nursing was always simultaneous with resting or with grooming of the pup. Females nursed their young an average of six times per day and each bout lasted about 9 minutes. The mean duration of food dives by females with young was 52 seconds. The peak period of birth was from December to February. Postpartum behavior of one female is described.
Two techniques have been used to obtain Physeter macrocephalus bearings, a directional hydrophone and a system of towed hydrophones. Directional hydrophones allow bearings to be measured directly, but necessitate stopping the survey vessel at each listening station. They are susceptible to boat and surface water noise and need to be rigidly mounted to the vessel. Towed hydrophone systems can be monitored while the boat is moving and are simple to deploy from any modest sized vessel. The collection of data does not require an experienced operator, but the determination of bearings relies on fairly complex signal processing. -from Authors
A three-dimensional array of hydrophones was anchored for 6 days (8 to 13 May 1971) in Kealakekua Bay on the island of Hawaii in order to listen to the underwater sounds of a resident population of spinner porpoises, Stenella cf. longirostris (Gray, 1828). Arrival-times for individual porpoise sounds were measured, and source locations were calculated to provide a three-dimensional indication of position for calling animals. Most sounds originated at depths less than 10 meters, and many of them were exchanges of sounds by porpoises within 10 to 15 meters of each other. Source level calculations indicated a wide range of levels that suggest intentional control of sound level. The three-dimensional array provided information that would not have been available by single hydrophone listening.
Horizontal directionality of ambient noise was measured at ranges up to
15 km from the south-eastern shore of Monterey Bay, California. Water
depths at the sites ranged from 8 to 175 m. A steerable cardioid
receiving pattern was formed using signals telemetered from dipole and
omnidirectional hydrophones suspended from tethered buoys. With no
nearby shipping, whenever the maximum of the cardioid pattern was
directed toward the beach, noise levels in the frequency range from 20
Hz to 70 Hz were greater than those obtained when the maximum was
directed seaward. This difference or anisotropy (seaward vs. shoreward),
which depends on range from the beach, on frequency and on surf
intensity, was 10 dB at 300 Hz at the 9 km site during very heavy surf.
Surf beat was clearly audible when the cardioid maximum was steered
shoreward at ranges as great as 2 km. During heavy surf, the
omnidirectional ambient noise levels also increased significantly in the
same frequency range at which the anisotropy is evident. The anisotropy
effects diminish both in magnitude and in frequency range with lower
wave height but are still observable during light surf. We have
concluded that intense breaking surf can contribute significantly to
ambient noise in fairly deep continental shelf waters.
False killer whales (Pseudorca crassidens) are deep-diving, pelagic, toothed whales that inhabit temperate and tropical oceans. Pseudorca prey on squid, large fish, and perhaps even dolphin (Tomich, 1986). They produce many types of sounds, including whistles, frequency-modulated sweeps, and pulses (Busnel and Dziedzic, 1968; Watkins, 1980).
It is commonly accepted that the ocean's ambient noise levels are rising due to increased human activities in coastal and offshore areas. It has been estimated that low-frequency noise levels increased more than 10 dB in many parts of the world between 1950 and 1975. [Ross, Acoustics Bulletin, Jan/Feb (1993)]. Several other sources cite an increase in manmade, or anthropogenic, noise over the past few decades. [D. A. Croll et al., Animal Conservation 4(1) (2001); Marine Mammal Commission Report to Congress (1999); C. W. Turl, NOSC Tech. Report 776 (1982)]. However, there are few historical records of ambient noise data to substantiate these claims. This paper examines several sectors of anthropogenic activities to determine their contributions to ambient noise. These activities include shipping, oil and gas exploration, military sonar development, and academic research. A series of indices for each of these industries is developed to predict ambient noise trends in the sea. It is found that the amount of noise generated by individual activities may have decreased overall due to new technologies and improved efficiency even if the intensity of such activities has increased.
In‐air and underwater sounds were recorded from Ross seals, O m m a t o p h o c a r o s s i, during January 1966 in the western Ross Sea, Antarctica, from Cape Hallet to Cape Adare. In‐air sounds from seals hauled out on ice ranged from 100–1000 Hz and included short (0.05–0.1 s) tonal pulses with downward sweeping frequency, and longer (1–1.5 s) calls with downward and upward sweeping frequency, somewhat like a police siren. Underwater vocalizations included pulses and siren calls that were similar to the in‐air sounds except that they had greater and mostly higher‐frequency ranges (1–4 kHz). The underwater calls were pulse modulated at a consistent rate of about 650/s, and usually were formed of two independently varying tones, each with separate sideband harmonics. Overlapping underwater sound sequences were heard from seals scattered throughout the areas sampled. The distinctive springtime siren calls would be useful for locating groups of these elusive seals.
The results of recent ambient‐noise investigations, after appropriate processing, are compared on the basis of pressurespectra in the frequency band 1 cps to 20 kc. Several possible sources are discussed to determine the most probable origin of the observed noise. It is concluded that, in general, the ambient noise is a composite of at least three overlapping components: turbulent‐pressurefluctuations effective in the band 1 cps to 100 cps; wind‐dependent noise from bubbles and spray resulting, primarily, from surface agitation, 50 cps to 20 kc; and, in many areas, oceanic traffic, 10 cps to 1000 cps. Spectrum characteristics of each component and of the composite are shown. Additional sources, including those of intermittent and local effects, are also discussed. Guidelines for the estimation of noise levels are given.
A model is developed for the acoustic source strength of blade rate line energy produced by single-screw merchant vessels. These source strengths are based on observed cavitation time histories on merchant vessels and on limitations imposed by considerations of propeller design procedures and ship vibration criteria. Relationships are given for the expected value of the blade rate source strength for ships of different lengths. These relationships are based on a small sample of merchant ship characteristics and are exercised for the estimated population of ships at sea. This calculation yields a statistical description of the distribution of source level and frequency of propeller blade rate acoustic energy for the fleet of signle-screw merchant vessels.
The ATOC acoustic source was installed on Pioneer Seamount during October and November 1995. The cable is terminated at the Pillar Point Air Force Station.
The applied research discussed in detail in this report supplements the work performed during the 1983 southbound and northbound migrations of the gray whale, Eschrichtius robustus, in the Monterey, California region. The objective of both phases has been to determine the degree of behavioral response of migrating gray whales to acoustic stimuli associated with oil and gas exploration and development activities. The results of that earlier work were presented in Bolt Beranek and Newman Inc. Report No. 5366* This companion document extends the 1983 research effort, adding to the statistical data base through measurements of behavioral response of the January 1984 southbound gray whale population to the same acoustic stimuli used in 1983 and to the operation of a single air gun. The playback sounds consisted of tape recordings of underwater acoustic signatures of a drilling platform, drillship, production plat-. form, semisubmersible drilling rig and a helicopter overflight. Analysis and interpretation of the resulting 1984 data both support and strengthen the findings of the 1983 research effort.
An investigation was made of the potential effects of underwater noise from petroleum-industry activities on the behavior of feeding humpback whales in Frederick Sound and Stephens Passage, Alaska in August, 1984. Test sounds were a 100 cu. in. air gun and playbacks of recorded drillship, drilling platform, production platform, semi-submersible drill rig, and helicopter fly-over noise. Sound source levels and acoustic propagation losses were measured. The movement patterns of whales were determined by observations of whale-surfacing positions.
Absolute sound pressure level measurements were made at sea on herds of four species of marine delphinids: the common dolphin, Delphinus delphis; the pilot whale, Globicephala macrorhynchus; the bottlenose dolphin, Tursiops truncatus; and the northern right whale dolphin, Lissodelphis borealis. Average source levels were similar for Delphinus, Globicephala, and Lissodelphis: 145-160 dB re 1 micropascal (per 120 Hz band). Peak levels varied from 170 to 180 DB for the four species, being the highest for Globicephala.
Comparison of long-term trends in mean wave height in the North Atlantic with values of annual mean atmospheric pressure gradient in the North Atlantic measured between the Iceland Low and the Azores High suggests, for the period of overlap between the data set of Bacon and Carter and of Sahsamanoglou (early 1950s to 1980), a correlation between these two measures. This paper, using monthly mean values of significant wave height (HS) derived from measurements at two sites, one oceanic (Ocean Weather Station Lima) and one coastal (Seven Stones Light Vessel), covering the period 1962–1988, investigates correlation between (firstly) annual mean values and (secondly) monthly mean values of HS and of pressure gradient. The annual mean values of pressure gradient are shown to be linked to the long-term changes in wave climate described by Bacon and Carter. The large annual cycles in the monthly mean values of both variates are found to be in phase; furthermore, correlation between the two variates independent of the annual cycle is found. Finally, the correlation between the annual means is used to generate a hindcast mean wave climate for Seven Stones Light Vessel (and also, tentatively, for the whole north-east Atlantic) from 1873 to the present, which suggests that present conditions are as high as have been observed since 1873.
Mass strandings of live whales have been explained by proposing many `natural' or human-related causes. I found that a recent stranding of Cuvier's beaked whale coincided closely in time and location with military tests of an acoustic system for submarine detection being carried out by the North Atlantic Treaty Organization (NATO).
Male humpbacks modify their sexual displays when exposed to man-made
noise.
SEISMOLOGYLast week an environmental group asked a federal judge to suspend a National Science Foundation (NSF)-funded sea-floor mapping expedition off Mexico that it claims led to the deaths of two whales. NSF rejects a link between the deaths and the air guns used by shipboard researchers to generate sound waves, but the incident has nonetheless reignited controversy over the impact of noise on marine mammals.
Preliminary investigations of the Atlantic walrus, Odobenus rosmarus rosmarus (Linnaeus)
- A G Loughrey
Loughrey, A. G. (1959). Preliminary investigations of the Atlantic walrus, Odobenus rosmarus rosmarus (Linnaeus). Canadian Wildlife Service Wildlife Management Bulletin Series 1, Number 14: 123
The effects of acoustic alarms on the by-catch of harbour porpoises in bottom set gill nets
- F Larsen
Larsen, F. (1997). The effects of acoustic alarms on the by-catch of harbour porpoises in bottom set gill nets. Danish Institute for Fisheries Research Report No 44-97pp
Functional aspects of cetacean communication Pp 270-307 in Cetacean Societies: Field Studies of Dolphins and Whales
- P L Tyack
Tyack, P. L. (2000). Functional aspects of cetacean communication. Pp 270-307 in Cetacean Societies: Field Studies of Dolphins and Whales. J. Mann (ed.), University of Chicago Press,Chicago
Mass stranding of cetaceans Pp 83-96 in CRC Handbook of Marine Mammal Medicine Acoustic tracking system fo rmonitoring under-ice movements of polar seals
- M T Walsh
- R Y Ewing
- G D Dell
Walsh, M. T., R. Y. Ewing, D. K. O'Dell and G. D. Bossart (2001). Mass stranding of cetaceans. Pp 83-96 in CRC Handbook of Marine Mammal Medicine. L. A. Dierauf and F. M. D. Gulland (ed.), CRC Wartzok, D., S. Sayegh, H. Stone, J. Barchak and W. Barnes (1992). Acoustic tracking system fo rmonitoring under-ice movements of polar seals. J Acous Soc Am 92(2): 682-687
Man-made Noise Pp 101-158 in Marine Mammals and Noise Ecology and behavior of the manatee (Trichechus manatus) in Florida
- C R J Greene
- S E W J Moore
- C R J Richardson
- C Greene
Greene, C. R. J. and S. E. Moore (1995). Man-made Noise. Pp 101-158 in Marine Mammals and Noise. W. J. Richardson, C. R. J. Greene, C. I. Malme and D. H. Thomson (ed.), Academic Press,San Deigo. rIWC/SC/56/E13 Hartman, D. S. (1979). Ecology and behavior of the manatee (Trichechus manatus) in Florida. Am. Soc. Mammal., Spec Publ. 5: 153 p