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Maritime traffic is a major contributor of anthropogenic disturbance for cetaceans, especially for coastal populations, such as that of resident common bottlenose dolphins (Tursiops truncatus) in the Sado estuary (Portugal). Animals have been found to adjust their vocal behavior by changing vocal rates, or call frequency and/or duration, to overcome masking effects of underwater noise. To evaluate the potential impacts of boat traffic on the acoustic behavior of these dolphins, emission rates and acoustic characteristics of whistles and burst‐pulsed signals were analyzed with and without boats operating nearby. In this study, no significant differences were found for emission rates of each type of vocal element in the presence of vessels. However, significant differences were found in acoustic parameters, namely changes in frequency and duration, for whistles and for pulsed sounds (creaks, grunts, squeaks, and gulps). These changes, such as a shift in vocal frequencies and production of shorter signals, may represent behavioral strategies to compensate for the noisy environment. Although resident bottlenose dolphins in the Sado region seem to have developed some tolerance to vessel noise, continuous noise exposure and noise‐induced frequency shifts in vocal outputs could have indirect fitness costs for this population. [ABSTRACT FROM AUTHOR]

The changes in underwater sound levels as commercial vessels navigate through shipping lanes in the inland waters around the Gulf of Georgia and San Juan Islands were assessed. These in-situ measures build on previous, more experimental evaluations. Recordings from three acoustic moorings at Boundary Pass, Turn Point and Haro Strait, southern Vancouver Island, British Columbia, were used to compare sound field measures at vessels' closest point of approach before, during, and following a turn. Vessel types assessed included tankers, bulkers, vehicle carriers, containerships, and passenger vessels. A multi-variate linear regression confirmed the relationship between vessel speed and sound levels, showing that the course of the vessel was also influential. The slowest transit speeds, yet highest broadband (10 Hz to 100 kHz) and vessel noise levels were recorded as they manoeuvred at Turn Point. Vessel-derived sound emissions in the mid-to high-frequencies were also considerable. [ABSTRACT FROM AUTHOR]

Patterns of underwater human-generated noise events and durations of noise-free intervals (NFIs) are soundscape metrics that can potentially affect animal communication and behavior. Due to the arduous task of manual analysis, these metrics have not been described in Glacier Bay National Park and Preserve (GBNP). To surmount this challenge, we created a machine-learning (ML) model trained on 18 hr of labeled audio samples from a hydrophone operating in GBNP since 2000. The validated convolutional neural net transfer-learning model (GBNP-CNN) was used to classify several categories of sound sources in nearly 9,000 hours of data from the same hydrophone, enabling our study of vessel noise between 2017 and 2020. We focused on the occurrence and duration of NFI and the hourly proportion (HP) of vessel noise. As expected, shorter NFI and higher HP were found during daytime hours. The GBNP-CNN F1 score was 75%, largely due to the model’s confusion of vessel noise with harbor seal roars. Therefore, NFI lengths should be considered minimum estimates, but the errors do not qualitatively affect diurnal or seasonal patterns. In 2018, mean daytime NFI during peak tourism months (June–August) was less than half the duration compared to May and September (1.3 min vs. 2.9 min). In 2020, when large-vessel tourism was substantially reduced but small-craft activity continued, we found that HP decreased in June–August. In conjunction with other soundscape metrics, monitoring NFI trends using ML models such as GBNP-CNN will provide crucial information for management and conservation of acoustic habitats and sensitive species in GBNP. [ABSTRACT FROM AUTHOR]

Animal vocalizations can evolve structural features as long-term adaptations to noisy environments. Using such signals, cetaceans could mitigate masking from vessel noise. This study investigates whether beluga whales (Delphinapterus leucas) use ultrasonic high-frequency burst pulse (HFBP) calls to communicate in noisy conditions. We identified HFBP calls in three populations: St. Lawrence Estuary, Eastern High Arctic-Baffin Bay, and Western Hudson Bay. Focusing on the industrialized St. Lawrence, we investigated the effects of vessel noise on HFBP call rates compared to other call types. Ultrasonic calls, spanning a bandwidth of 36.4±6.5 to 144 kHz (Nyquist frequency), comprised 13% of the St. Lawrence beluga repertoire (n=25,435). Noise events (n=21) were defined as periods when at least one vessel was visible within 2 km of the hydrophone while belugas were within 500 m. Sound pressure levels were measured before, during, and after exposure. Generalized linear mixed models revealed consistent HFBP call rates before, during, and after vessel noise exposure, while contact calls and other call types declined during exposure (n=4,528). These findings suggest that ultrasonic signals that evolved in the Arctic-where ice-associated noise may have created a need for high-frequency communication-remain a viable communication channel in vessel noise, allowing belugas to exploit these signals to maintain communication. Understanding how belugas utilize signals in noisy environments can inform conservation strategies for noise-impacted marine mammals., (© 2025. Published by The Company of Biologists.)

Patterns of underwater human-generated noise events and durations of noise-free intervals (NFIs) are soundscape metrics that can potentially affect animal communication and behavior. Due to the arduous task of manual analysis, these metrics have not been described in Glacier Bay National Park and Preserve (GBNP). To surmount this challenge, we created a machine-learning (ML) model trained on 18 hr of labeled audio samples from a hydrophone operating in GBNP since 2000. The validated convolutional neural net transfer-learning model (GBNP-CNN) was used to classify several categories of sound sources in nearly 9,000 hours of data from the same hydrophone, enabling our study of vessel noise between 2017 and 2020. We focused on the occurrence and duration of NFI and the hourly proportion (HP) of vessel noise. As expected, shorter NFI and higher HP were found during daytime hours. The GBNP-CNN F1 score was 75%, largely due to the model’s confusion of vessel noise with harbor seal roars. Therefore, NFI lengths should be considered minimum estimates, but the errors do not qualitatively affect diurnal or seasonal patterns. In 2018, mean daytime NFI during peak tourism months (June–August) was less than half the duration compared to May and September (1.3 min vs. 2.9 min). In 2020, when large-vessel tourism was substantially reduced but small-craft activity continued, we found that HP decreased in June–August. In conjunction with other soundscape metrics, monitoring NFI trends using ML models such as GBNP-CNN will provide crucial information for management and conservation of acoustic habitats and sensitive species in GBNP.

In 2014, the South African government launched 'Operation Phakisa' under which port developments play a significant role in supporting ocean economic growth. These developments will likely increase vessel traffic to and from South African ports, making it imperative to monitor for changes in underwater sound budgets with potential negative effects on marine life. However, no soundscape studies have been conducted around South Africa, resulting in an absence of baseline measurements. This study provides a first description of the underwater soundscape in St. Francis Bay and Algoa Bay, Eastern Cape. Soundscape measurements identified major soundscape contributors, temporal patterns in broadband sound levels, and underlying environmental drivers. Applicability of modelled vessel noise and wind noise maps to predict large-scale spatial variation in sound budgets was assessed. Our study shows that sounds from biological sources and wind dominated at all recording sites, with fish choruses driving temporal patterns as a function of time of year and position of the sun. Sound from vessels was present at all sites but most notable in long-term spectral levels measured in Algoa Bay. Sound propagation models predicted a further increase in the contribution of vessel noise towards shipping lanes and east Algoa Bay. Our study provides a building block to monitor for shifts in sound budgets and temporal patterns in these two bays under a developing ocean economy. Furthermore, our study raises concerns that vessel noise is likely a significant contributor in shallow waters elsewhere along the South African coast where vessel density is known to be higher (i.e., Durban and Cape Town). [ABSTRACT FROM AUTHOR]

Noise generated by ship traffic is increasing around the world. Hence, there is need to effectively evaluate anthropogenic noise levels in marine habitats. In this study, the noise contribution of ships in the Santiago–Manzanillo bay complex, on the Pacific coast of central Mexico, was assessed. The semienclosed bay complex is one of the most important commercial ports in Mexico, and it is an area with high biological richness and tourism demand, including demand by the informal humpback whale watching industry. Bottom-fixed recording systems were deployed at the entrance to the bay, near the commercial port (Manzanillo Bay), and within the tourist area (Santiago Bay). Monthly acoustic records were obtained from September 2015 to August 2016. Boat categories confirmed by visual sightings were associated with their acoustic signals. According to the diagnostic frequency range, vessel noise was classified into noise coming from large ships (50–220 Hz) or from small vessels (290–500 Hz). Large ships were always detected at both stations, while, as expected, small vessels were more common in tourist areas. Vessel noise in the entire area ranged from 130 to 170 dB (RMS re 1 μPa) and was present up to a median of 81.8% of the time throughout the year, with higher prevalence from 1200 to 1600 hours. Marine traffic activities were constant in the area, but frequency content and sound pressure levels were not equally distributed across the bay. Therefore, it is important to consider the possible differential impacts on marine fauna inhabiting the area.

Models of cetacean communication range reductions associated with anthropogenic noises are complex. They often require assumptions related to the hearing abilities and vocalization source levels of the species concerned. The maximum range of a call is limited by transmission losses which reduce the signal amplitude until it is masked by ambient noise. We propose a simple method to estimate the proportional reductions in communication range associated with anthropogenic noise sources, relative to the maximum range under ambient noise-level conditions, that can be calculated using only noise-level measurements and is independent of the hearing sensitivity of the species concerned. The remaining communication range (% of maximum) = 10-Δ/k x 100 where Δ is the dB difference between the anthropogenic noise level and the ambient noise level while assuming a spreading loss of klog10(range). This enables indexing the remaining communication ranges and, by observation of plots of the data, identifying duty cycles associated with anthropogenic noises. The proposed method was tested with the analysis of underwater ferry noise in a baleen whale habitat in the Bay of Fundy, Canada. The relative communication range and duty cycle were estimated using data from autonomous underwater recorders. Three one-third octave band levels at the same frequencies as vocalizations of the local mysticete species were analyzed. Calls at 20 Hz would not be masked by ferry noises. Calls at 125 and 500 Hz would have severely reduced communication ranges for eight one-hour periods per day when the ferries were operating. Collection and analyses of only noise-level data are faster and much less expensive than more sophisticated studies. Computing remaining communication range analyses may be a useful first step in identifying and ranking anthropogenic noise sources and their potential for animal communication masking. [ABSTRACT FROM AUTHOR]

In 2014, the South African government launched ‘Operation Phakisa’ under which port developments play a significant role in supporting ocean economic growth. These developments will likely increase vessel traffic to and from South African ports, making it imperative to monitor for changes in underwater sound budgets with potential negative effects on marine life. However, no soundscape studies have been conducted around South Africa, resulting in an absence of baseline measurements. This study provides a first description of the underwater soundscape in St. Francis Bay and Algoa Bay, Eastern Cape. Soundscape measurements identified major soundscape contributors, temporal patterns in broadband sound levels, and underlying environmental drivers. Applicability of modelled vessel noise and wind noise maps to predict large-scale spatial variation in sound budgets was assessed. Our study shows that sounds from biological sources and wind dominated at all recording sites, with fish choruses driving temporal patterns as a function of time of year and position of the sun. Sound from vessels was present at all sites but most notable in long-term spectral levels measured in Algoa Bay. Sound propagation models predicted a further increase in the contribution of vessel noise towards shipping lanes and east Algoa Bay. Our study provides a building block to monitor for shifts in sound budgets and temporal patterns in these two bays under a developing ocean economy. Furthermore, our study raises concerns that vessel noise is likely a significant contributor in shallow waters elsewhere along the South African coast where vessel density is known to be higher (i.e., Durban and Cape Town).

The aim of this study was to explore an emerging discipline addressing the impact of anthropogenic noise on larval stages of marine organisms. We assessed the influence of boat noise on the feeding behaviour of the pelagic larvae of winter flounder (Pseudopleuronectes americanus, Walbaum, 1792). The hypothesis was that boat noise influences the feeding behaviour of P. americanus flounder larvae independently of prey density. Aquaria containing P. americanus larvae were placed in water baths in which boat noise was diffused for the "noise" treatment and compared to control aquaria with no sound emissions. Larvae were filmed using cameras placed above the aquaria and their behaviour was recorded. Larvae exposed to anthropogenic noise displayed significantly fewer hunting events than controls, and their stomach volumes were significantly smaller. This noise effect was the same at all prey densities used, suggesting that larval feeding behaviour is negatively impaired by anthropogenic noise. [ABSTRACT FROM AUTHOR]

Previously, catchabilty of walleye pollock was estimated for the accounting trawl RT/TM 57/360 by results of acoustic measurements of fish density in the towed layer under fishing vessel. However, fish reaction to noise field ahead of vessel was not accounted in that experiment. Besides, distortion of initial distribution of fish by the vessel noise could cause an error in fish stock estimations by methods of echo integration. Data of new experiment conducted for estimation of fish reaction to the vessel noise are presented using independent floating buoy equipped by scientific echo sounder. Distance of walleye pollock reaction to the vessel noise was estimated as 140-180 m that corresponds to the calculated value (150 m) used in modeling. Distortion of typical fish distribution was considerable: the fish density decreased in the upper layer and gradually increased in deeper layers as the fish moved down. The density decreasing in the layer 0-100 m was evaluated as 0.56, i.e. the echo integration method underestimated the fish density on more than 40 %, the decreasing in the layer 100-200 was less significant (0.86). Fish moved down under the noise effect in 10 times faster than at their daily vertical migration. The experimental data on walleye pollock density change under influence of passing fishing vessel are compared with the modeling results. Estimations of catchability coefficient for the accounting trawl РT/TM 57/360 are corrected taking into account the depth of trawling. The corrected coefficients of catchability for walleye pollock vary from 0.01 at the sea surface to 0.85 at the depth equal to the distance of its reaction to the noise.

This paper proposed an improved prediction method of inland waterway vessel noise considering the effects of water surface adsorption and embankment shielding. The method was established on the basis of the UK Calculation of Road Traffic Noise (CoRTN) method, and the effects of water surface adsorption and embankment shielding were integrated into the governing equations. The developed method was validated using the data measured at the 40 monitoring points along Da Yunhe Channel in China. The results showed that the improved method had a higher accuracy and precision than that of the unmodified CoRTN method. The predicted noise exposure level by the unmodified CoRTN method correlated with the measured values with an R2 of 0.74569, which was enhanced to 0.86457 by the improved method. The current research is the prime to forecast river vessel noise level on the basis of the CoRTN method considering water surface adsorption and embankment shielding influences in China. It is expected that the modified method could be a new tool for estimating vessel noise effect on the inhabitant around the urban inland waterways. [ABSTRACT FROM AUTHOR]

Recovery of the endangered Southern Resident killer whales of the Salish Sea is impeded by threats such as vessel disturbances and noise. Reduction of vessel disturbances is key for recovering the population, but recreational vessel operators have high rates of noncompliance with regulations intended to reduce noise. Through a survey of 115 recreational boaters in Washington state, this study was an exploratory analysis of the normative and instrumental factors that may influence compliance. Recreational boaters self-reported having high levels of compliance with vessel regulations. They shared characteristics including a strong sense of responsibility to follow the rules, support for vessel regulations, concern about orca conservation, and a belief that other boaters do not comply with vessel regulations. These characteristics may predispose them to be more motivated by normative factors, such as a sense of personal responsibility, social norms, and participation in rulemaking, rather than instrumental factors based in enforcement and deterrence. This reflects how normative motivations may be more important for groups with certain characteristics, illuminating differences in motivations within a population of resource users. Due to this, management interventions should address both normative and instrumental motivations for compliance. Interventions that appeal to normative motivations based on social norms and personal responsibility, or education and outreach that fill knowledge gaps about regulations, may most influence the behavior of the boaters surveyed in this study. Nevertheless, enforcement and deterrence may still be useful for shaping compliance by boaters who are less represented in this study, such as tourists or fishers. • Boaters reported high levels of compliance, motivated by normative factors. • Certain characteristics predispose boaters to be motivated by normative factors. • Boaters had a strong sense of responsibility and concern for orcas. • Education and outreach are important to fill gaps in awareness about regulations. • Interventions based on normative factors should be complemented by enforcement. [ABSTRACT FROM AUTHOR]

Vessel noise is an acute and chronic stressor of a wide variety of marine fauna. Understanding, modelling and mitigating the impacts of this pollutant requires quantification of acoustic signatures for various vessel classes for input into propagation models and at present there is a paucity of such data for small vessels (−1) by each vessel at Lizard Island, Great Barrier Reef, Australia. Radiated noise levels (RNLs) and environment-affected source levels (ASLs) determined by linear regression were estimated for each vessel and speed. From the slowest to fastest speeds, median RNLs ranged between 153.4 and 166.1 dB re 1 µPa m, whereas ASLs ranged from 146.7 to 160.0 dB re 1 µPa m. One-third octave band-level RNLs are provided for each vessel–speed scenario, together with their interpolated received levels with range. Our study provides data on source spectra of small vessels to assist in understanding and modelling of acoustic exposure experienced by marine fauna.

In commercial fishery, catching properties of fishing gears are developed mostly for effective catch of fish, rather than for precise measurement of fish distribution density in water, so a problem of catchability exists and this parameter should be determined for each fishing gear. Various methods for estimation of catchability for trawl survey systems are considered. The experimental method of its estimation (comparing of fish density in towed volume determined by other tools with trawl catch) is considered as the most authentic. Scheme and algorithm of the measurements and calculations are described for standard hydroacoustic tools, as scientific echosounder ЕК-60, and software is developed for recalculation of trawl catch to equivalent acoustic units of fish density in the towed volume of water. Results of the catchability estimation for the trawl RT/TM 57/360 used for walleye pollock stock assessment in the Okhotsk Sea are analyzed. Mean value of the catchability coefficient in this case varies from 0.42 to 0.81, generally increasing with depth but decreasing both at the sea surface and on the depth > 200 m. These results correspond well with the model of fish behavior in the noise field of vessel: the low catchability at the sea surface and its increasing with depth could be caused by avoiding reaction of fish to the noise and its moving to deeper layers. Besides, the catchability coefficient for pollock depends on fish size and time of day: it increases with the fish length but decreases for the largest individuals. Influence of the noise field of vessel on selectivity of survey trawls is modeled and there is shown that the depths of the maximum concentration of small-sized and large-sized pollock do not coincide. The developed software and received results are universal means for estimation of the catchability for trawls in all conditions of trawling, they allow to choose optimum mode for survey trawling in dependence on fish species, depth of trawling, and type of vessels and trawl.

Underwater noise radiated by two medium-tonnage research vessels of Pacific Fish. Res. Center (TINRO) belonged to the same project «Atlantic-833» (RV TINRO and Professor Kaganovsky) is measured by a calibrated hydrophone system. Tools and methods of the noise measurement and methods of the data processing are described in details. Diagrams of the noise spatial distribution, its amplitude-time and spectral-power parameters are presented and compared with those recommended by ICES for fishery research vessels and with similar parameters of other vessels. The maximum noise level is registered abeam of the vessels; the sound interference is observed at the sea surface in the beam vicinity. The noise spectrum is limited by the frequency 2000 Hz with high power in the band < 500 Hz; the spectral power decreases by 3 dB per octave for the frequencies > 200 Hz. The noise field at the sea surface has a classic «butterfly» shape for the frequency range 600-2000 Hz. The noise in 1/3-octave bands exceeds the level recommended by ICES for research vessels on 20-22 dB for the frequencies < 200 Hz and on 10 dB for the frequencies > 500 Hz, it exceeds the noise of diesel-electric RV Oscar Dyson (USA) on 18-24 dB for the frequencies < 1000 Hz and is similar to noise of factory trawler Prometey (USSR) and RV Miller Freeman (USA) for the frequencies most sensitive for fish. Distance of fish reaction to the sonar noise is determined for mass commercial species: it is the largest among research vessels for cod and pollock but is shorter than that one for RV Miller Freeman for herring (commercial trawler Prometey has the largest distance for all these species). For salmons, the distance of their reaction to sonar noise of TINRO’ vessels does not exceed that one recommended by ICES (20 m).

Vessel traffic is one of the most wide-spread anthropogenic contributors to ocean noise worldwide and has the potential to alter ecosystems upon which cetaceans and other acoustically sensitive marine organisms rely. Canada's S G aan K inghlas-Bowie Seamount Marine Protected Area (SK-B MPA) is one such area whose productive ecosystem could benefit from greater monitoring of human induced threats in order to inform management. Despite earning official designation as a Marine Protected Area under the Oceans Act in 2008, little remains known about vessel traffic in the region and the associated potential impacts on vulnerable marine species. Therefore, to increase our understanding of vessel traffic and accompanying noise at SK-B MPA, satellite AIS and acoustic data were investigated. The results of this study suggest that variations in ambient sound levels in the region are driven by near and distant shipping events, thus having implications for future management of the MPA. [ABSTRACT FROM AUTHOR]

This study investigated the emission of subaquatic noise from recreational tourism motorboats, schooners and a sea-bottom mounted water pump. Analyses demonstrated alterations in several whistle (IF: t = 2.42, P = 0.015; FF: t = −2.22, P = 0.025) and calls patterns (MIF: t = −3.13, P = 0.001; MAF: t = −3.49, P = 0.0005; FD: t = −2.21, P = 0.027; D: t = 2.89, P = 0.004), caused primarily by motorboats. Duration of clicks was also modified (D: t = −3.85, P = 0.0001), mainly by the water pump. The frequency range of all noises (0.43–35.8 kHz) overlaps that used by dolphins (1–48 kHz), causing sound emissions changes, with a considerable increase in number of whistles and a reduction in clicks trains. These changes may be a strategy developed by these dolphins to overcome the noise band. Mitigation measures, such as boating regulations and environmental education for the local community, boaters and tourists are needed to conserve the species. The Guiana dolphin population is apparently already suffering, evidenced by diminished residence time and reduced number of individuals entering the inlet during the presence of pleasure craft. [ABSTRACT FROM PUBLISHER]

Danish coastal waters are a hotspot for recreational boating and harbour porpoises (Phocoena phocoena), but as there is little data on the boats' speeds and distributions, it is difficult to determine where porpoises are likely to be affected by boat noise. To gain knowledge on the potential impacts of small boats we 1) used coastal observations to assess how boat speed is related to boat size, type, distance to marinas, and wave height, and 2) used satellite images to assess the spatial distribution of small boats in Kattegat, the Sound, the Belt Sea and the Western Baltic areas (see map in Sveegaard et al., 2015). This made it possible to determine how the probability of observing boats was related to distance to the coast and number of people living within a radius of 5 km from a given area. We found that boat speeds varied among marinas and that speed was positively correlated with distance to the marina. The relationship between boat speed and size depended on boat type, with motorboats being the fastest. The satellite image analysis showed that motorboats were the dominant type in coastal waters, constituting 61.4% of the observed boats. The probability of observing boats on a satellite image covering 0.25 km2 dropped from 0.13 by the shore to 0.04 at a distance of 5 km from shore. The probability of observing boats was >10% in 6.6% of the study area, and the probability of observing boats and porpoises in the same area was >10% in 3.0% of the study area. Coastal waters are important habitats for many aquatic species, e.g., fish, invertebrates and porpoises, that use sound for communication or navigation. Our study uses a combination of observation and satellite data to identity areas where boats overlap with harbour porpoise presence and thus where the animals may be affected by boat noise. The study also illustrates how combining these two methods can yield important information on the potential impacts of boats on wildlife. • Speed and distribution of small boats were investigated in Danish waters. • Boat speed increased with distance to marinas and varied among boat types. • Boats were most common close to the coast and near densely populated areas. • Harbour porpoises had a risk >10% of exposure to boats in 3% of the study area. • Boat noise may affect porpoises in coastal areas between Sweden and Denmark. [ABSTRACT FROM AUTHOR]

Southern right whales (Eubalaena australis) are listed as Endangered under the Australian EPBC Act 1999. They migrate to shallow, coastal waters during the winter to mate, calve and nurse their young. During this time, they are easily accessible to the boat-based whale-watching industry. The aim of the study was to determine if whale-watching at 300 m distance affects the behaviour of southern right whales. To achieve this, behavioural focal follows on mother-calf pairs were conducted using unmanned aerial vehicles (UAVs) in the presence and absence of a commercial whale-watching vessel. There was no significant effect of phase (control, before, during, after) on the whales' respiration rate, swim speed, nursing rate and duration, maternal rate of active behaviours, tactile contact or calf pectoral fin contact. There was a significant reduction in resting between control and after phases, for both mothers (from 62% to 30%) and calves (from 16% to 1%). At 300 m distance and slow speed, vessel noise was measured to be slightly above ambient noise at the lower TOL 0.25 kHz band, however, vessel noise was masked by ambient noise within the higher frequency TOL 2–10 kHz bands. A factor which may have contributed to a decline in resting after whale-watch approaches, was an increase in vessel speed upon departure, which consequently increased vessel noise. Based on this, we recommend that vessels maintain a slow speed (e.g., ≤10 knots) within 1 km distance from the whales whilst conducting whale-watch activities. • There was no effect of whale-watching on respiration rate, swim speed or nursing. • Resting for mothers halved after whale-watching compared to control data. • Resting for calves declined to near null after whale-watching compared to control. • Fast departure speeds after encounters appear to disturb resting behaviour. • We recommend that vessels maintain slow speed within 1 km to whales. [ABSTRACT FROM AUTHOR]

Mobile hydroacoustic surveys are increasingly used to assess the distribution and abundance of freshwater fish; yet, fish may avoid moving vessels, potentially introducing bias in these assessments. In this study, avoidance in boreal lakes and reservoirs was quantified by developing a simple method based on paired drift:drift (D:D) and drift:motor (D:M) transects. Two systems in eastern Manitoba, Canada were studied: Lac du Bonnet reservoir and Nopiming. Acoustic data were collected using a digital DTX echosounder (BioSonics, Seattle, WA, USA), with a downward facing 200-kHz split-beam transducer, deployed from 5.5-m vessels (Boston Whalers) modified for acoustic research. An avoidance coefficient ( Ac) was developed based on comparisons of acoustic fish densities while the vessel moved over the same transects by drifting, and by motoring at survey speeds. Ac did not differ significantly from 1 (no avoidance) at Nopiming (median of 0.81, n = 13), but did at Lac du Bonnet (median of 0.51, n = 31, P < 0.05). Variability in Ac was as high in transect pairs and was unrelated to fish depth (mean 6.9 m at Lac du Bonnet; 13.1 m at Nopiming) or survey speed (up to 3.70 m·s−1, 7 knots). Results indicated that fishes did not dive in the presence of the motoring vessel, nor was avoidance size-based. We did not detect any evidence of fish attraction to our drifting vessel. Our results suggest that boat avoidance during acoustic surveys of shallow boreal lakes may vary in relatively similar water bodies but can be quantified experimentally. [ABSTRACT FROM AUTHOR]

Globally billions of dollars are spent each year on attempting to reduce marine biofouling on commercial vessels, largely because it results in higher fuel costs due to increased hydrodynamic drag. Biofouling has been long assumed to be primarily due to the availability of vacant space on the surface of the hull. Here, it is shown that the addition of the noise emitted through a vessel’s hull in port increases the settlement and growth of biofouling organisms within four weeks of clean surfaces being placed in the sea. More than twice as many bryozoans, oysters, calcareous tube worms and barnacles settled and established on surfaces with vessel noise compared to those without. Likewise, individuals from three species grew significantly larger in size in the presence of vessel noise. The results demonstrate that vessel noise in port is promoting biofouling on hulls and that underwater sound plays a much wider ecological role in the marine environment than was previously considered possible. [ABSTRACT FROM AUTHOR]

Underwater noise is increasing globally, largely due to increased vessel numbers and international ocean trade. Vessels are also a major vector for translocation of non-indigenous marine species which can have serious implications for biosecurity. The possibility that underwater noise from fishing vessels may promote settlement of biofouling on hulls was investigated for the ascidianCiona intestinalis. Spatial differences in biofouling appear to be correlated with spatial differences in the intensity and frequency of the noise emitted by the vessel’s generator. This correlation was confirmed in laboratory experiments whereC. intestinalislarvae showed significantly faster settlement and metamorphosis when exposed to the underwater noise produced by the vessel generator. Larval survival rates were also significantly higher in treatments exposed to vessel generator noise. Enhanced settlement attributable to vessel generator noise may indicate that vessels not only provide a suitable fouling substratum, but vessels running generators may be attracting larvae and enhancing their survival and growth. [ABSTRACT FROM AUTHOR]

Underwater sound plays an important role in the settlement behaviour of many coastal organisms. Large steel-hulled vessels are known to be a major source of underwater sound in the marine environment. The possibility that underwater sound from vessels may promote biofouling of hulls through triggering natural larval settlement cues was investigated for the mussel, Perna canaliculus. The mussel larvae showed significantly faster settlement when exposed to the underwater noise produced by a 125-m long steel-hulled passenger and freight ferry. Median time to attachment on the substrata (ie settlement) was reduced by 22% and the time taken for all experimental larvae to settle was reduced by 40% relative to a silent control. There was no difference in the survival of the mussel larvae among the various noise treatments. The decrease in settlement time of the mussel larvae appeared to correlate with the intensity of the vessel sound, suggesting that underwater sound emanating from vessels may be an important factor in exacerbating hull fouling by mussels. [ABSTRACT FROM AUTHOR]

Abstract: There is concern that research vessels used in fish stock appraisals may have biased data due to fish avoidance reaction. One possible mechanism inducing this avoidance reaction is tonal noise. This paper assesses fish reaction to vessel noise on the basis of a detailed paper on the tonal auditory characteristics of cod . Specifically, narrow band underwater radiated noise from certain research vessels, but mainly “R.V. Scotia”, is used to establish a cod reaction range. This is then compared to the calculated reaction range using a 1/3rd octave band assessment as set forward in International Council for the Exploration of the Sea (ICES) Cooperative Research Report No. CRR 209. These comparisons were also carried out for another low-noise research vessel, namely “CEFAS Endeavour”. It is tentatively concluded from this paper that, based upon the “30dB above hearing threshold” criterion, vessel tonality is not a strong mechanism for fish reaction to the low-noise ICES compliant vessels. However, it should be appreciated that this generalisation is based upon one (sensitive) specific species of fish and two specific research vessels. It is considered that further analysis should be carried out on other commercially important, but noise-sensitive fish, such as herring. Also, narrow band underwater noise should be investigated for other fisheries research vessels – ideally including those where strong fish reactions have been observed viz. G.O. Sars and Oscar Dyson. It should also be noted that, in this paper, each tone has been considered separately from all others; whereas, in reality, vessel noise is rich in tones and harmonics. This paper has attempted to separate out the tonal audibility aspect from the general issue of vessel broadband radiated noise by solely looking at the tonal level above the spectrum level to gain some insight into the importance of this issue. Comments are also made on various issues including masking noise, very low frequency tonal noise and the associated issue of particle acceleration sensitivity for cod. [Copyright &y& Elsevier]

The article presents a study which investigates the effect of underwater noise pollution to cetacean. It notes that the study measured masking levels to assess the relative impact of noise from small vessels on the communication range of free-ranging delphinids. It states that small vessels with outboard engines having more than five knots of speed and approaches a distance closer than 50 meters to delphinids will reduce their acoustic communication range. It also states that noise emissions from the vessel should be measured in concluding its impact on cetaceans. It found that such noises significantly affect the communication of delphinids. Moreover, the study suggests on the implementation of vessel-quieting techniques and noise standards along with whale-watching guidelines.

The power of modern research vessels using diesel engines means significant levels of noise may be radiated underwater. At low frequencies a surveying vessel must not cause fish avoidance behaviour when it is using trawl or acoustic assessment methods. All the main mechanisms that form the essential propulsion system are described and discussed in terms of underwater radiated noise. Diesel engines, generators and propulsion motors contribute significantly to the low frequency spectrum and an illustration is given of underwater noise when an unsuitable propulsion system is used. Avoidance behaviour by a herring school is shown due to a noisy vessel, by contrast there is an example of no reaction of herring to a noise-reduced vessel. Propellers are major sources of both low and high frequency noise. The latter should not reduce echo sounder detection range, nor contaminate echo integrator recordings. Underwater noise levels from four vessels with different machinery and propulsion characteristics are seen in relation to ambient noise levels at 18 kHz. Fish detection is examined in relation to sea background noise and vessel self-noise. Calculated detection ranges for fish target strength classes from –30 to –60 dB at 38 kHz are shown for six vessels travelling at 11 knots, based on self-noise measurements. Echo sounder noise levels from several vessels at 120 and 200 kHz are tabulated. Beyond 100 kHz the effect of vessel-radiated noise is usually insignificant; levels up to that frequency are proposed in the International Council for the Exploration of the Sea (ICES) Cooperative Research Report No. 209 of 1995. [Copyright &y& Elsevier]

The autonomous underwater vehicle (AUV) Autosub-2 was deployed on eight missions ahead of RRS James Clark Ross in the northern Weddell Sea and in the Bransfield Strait, Southern Ocean, to assess avoidance of the research vessel by Antarctic krill Euphausia superba. The AUV was equipped with the same type of scientific echosounder as the research vessel (Simrad EK500 operating at 38 and 120 kHz) and measured the density of krill along transect acoustically (g m−2 wet mass) prior to the ship’s arrival. We hypothesised that if krill avoided the ship, perhaps in response to radiated noise, then the ship should detect less krill than the AUV which is known to have much lower noise levels than the ship. We were unable to detect any significant difference between the density of krill detected by the ship or the AUV, either at the transect level or at finer scales within transects. We conclude, therefore, that avoidance by krill of RRS James Clark Ross will not significantly bias acoustic estimates of krill abundance by this vessel. [Copyright &y& Elsevier]

Passive acoustic recorders were deployed over two years (February 2018–March 2020) in the Salish Sea to monitor the underwater soundscape. Seasonal cycles and differences between the open Strait of Juan de Fuca and protected inner waterways were pervasive during this period. A comparison between natural and human-derived noise demonstrated the impact of anthropogenic activities on the sound field. Elevated ambient noise levels during winter resulted predominantly from greater sea states and storm events. Abiotic additions were defined through correlations to wind speed, wave and precipitation measures. Vessel noise was a pervasive anthropogenic addition; commercial vessel noise was consistently present, whereas smaller vessels showed weekly and diurnal patterns, especially during the summer when their presence increased. A better understanding of the different soundscape constituents, and when each dominates, is crucial to understanding the human impact on underwater ecosystems and the organisms within them, leading to more effective mitigation measures. • Seasonal patterning in soundscape of the Salish Sea dominates. • Frequency range metrics used to describe natural and anthropogenic inputs • Generally elevated sound field in winter, predominantly from abiotic sources • Commercial vessel input is constant; smaller vessels add notably in the summer. • Spatial distinction between western Juan de Fuca and more protected inner waterways [ABSTRACT FROM AUTHOR]

Vessel noise is an acute and chronic stressor of a wide variety of marine fauna. Understanding, modelling and mitigating the impacts of this pollutant requires quantification of acoustic signatures for various vessel classes for input into propagation models and at present there is a paucity of such data for small vessels (<25 m). Our study provides this information for three small vessels (<6 m length and 30, 90 and 180 hp engines). The closest point of approach was recorded at various ranges across a flat, ≈10 m deep sandy lagoon, for multiple passes at multiple speeds (≈5, 10, 20, 30 km h−1) by each vessel at Lizard Island, Great Barrier Reef, Australia. Radiated noise levels (RNLs) and environment-affected source levels (ASLs) determined by linear regression were estimated for each vessel and speed. From the slowest to fastest speeds, median RNLs ranged between 153.4 and 166.1 dB re 1 µPa m, whereas ASLs ranged from 146.7 to 160.0 dB re 1 µPa m. One-third octave band-level RNLs are provided for each vessel–speed scenario, together with their interpolated received levels with range. Our study provides data on source spectra of small vessels to assist in understanding and modelling of acoustic exposure experienced by marine fauna. [ABSTRACT FROM AUTHOR]

Acoustic data was collected across 15 sites distributed through the coastal area of Rio de Janeiro, Brazil, encompassing regions of different natural characteristics. Noise levels and the acoustic complexity index were calculated. Quantity and composition of anthropogenic sound sources varied across recording sites, with at least one type of sound source being registered in each location. A cluster analysis using third-octave levels from eight frequency bands divided recording sites into two groups, one considered as impacted by anthropogenic noise and the other as less-impacted. The noisiest recording locations were those with higher numbers of anthropogenic sound sources, specifically large ships. It was evidenced that anthropogenic noise affects not only noise levels, but also low-frequency acoustic complexity, which decreased in the presence of vessel traffic. The constant noise input of human activities tended to mask natural variability in the soundscape at lower frequencies. • Previously unexplored coastal areas were investigated. • Noise levels and complexity index were calculated for 15 coastal locations. • Different locations were grouped together by level of noise impact. • Artificial sound sources increased noise and decreased complexity. • Anthropogenic noise decreased soundscape variability. [ABSTRACT FROM AUTHOR]

Large commercial vessel traffic is expected to continue growing over the next decades, making marine habitats noisier. This additional vessel noise could prevent the recovery of endangered marine species and populations and become a threat to others. Spatially constricted areas are places where both maritime traffic and species can concentrate, increasing the risks of negative impacts. We assessed sound amplitude and temporal trends in the daily movement of large ferries, container ships, bulkers, and tankers in the Cabot Strait, the main entrance way to the Gulf of St. Lawrence Seaway in Atlantic Canada. We used Automatic Identification System (AIS) and geophysical data as input for an acoustic model to produce 12 scenarios representing different regimes of vessel traffic and estimated equivalent continuous noise levels (L eq) over a 24-h period. Our results show that a 50% increase from the estimated median number of large vessel transits could lead to a 23% increase in the area affected by vessel noise, while doubling the number of transits could lead to a 58% increase. Cetaceans located <7–8 km from a vessel could experience sound pressure levels above the U.S. 120 dB re 1 μPa threshold for the onset of behavioral disturbance. Introducing speed restrictions could help reduce the acoustic footprint of the four vessel classes in this area and limit possible negative effects on marine mammals and other marine species. Image 1 • Large commercial vessel traffic has been growing in the Cabot Strait over the period 2013–2016. • Cetaceans located < 7–8 km from a vessel in the study area can be affected by behavioral disturbance. • Median levels of traffic can increase noise above background levels over 33% of the study area. • Doubling merchant vessels traffic could lead to a 23% increase in the area affected by noise. [ABSTRACT FROM AUTHOR]

This study developed a prediction model for estimating urban inland waterway traffic noise emission level. The model based on the Scandinavian Nord 2000 method, which was modified by adding two categories of traffic flow, comprising light and heavy vessels, as well as vessel average speed to the calculating equations. Meanwhile, the influences of the water surface and embankment were also considered in the established model. Model verification was conducted using the data surveyed at the 30 sampling points of Danjinlicaohe Channel in Jiangsu Province of China. A high correlation was found between the predicted and measured noise values L Aeq (Pearson correlation coefficient = 0.949, p < 0.01). And the mean difference between the predicted and measured noise values was 0.16 ± 1.28 dBA. The results showed that the proposed model had higher accuracy than the unmodified Nord 2000 method and can be applied for predicting vessel noise exposure level on inland waterway of China. Image 1 • An inland waterway traffic noise prediction model is developed for use in China. • The effects of water surface attenuation and embankment shielding are assessed. • The hourly basic noise level of vessel is modified. • The comparison has proved that the improved method has better precision and accuracy. [ABSTRACT FROM AUTHOR]