The number of marine watercraft is on the rise-from private boats in coastal areas to commercial ships crossing oceans. A concomitant increase in underwater noise has been reported in several regions around the globe. Given the important role sound plays in the life functions of marine mammals, research on the potential effects of vessel noise has grown-in particular since the year 2000. We provide an overview of this literature, showing that studies have been patchy in terms of their coverage of species, habitats, vessel types, and types of impact investigated. The documented effects include behavioral and acoustic responses, auditory masking, and stress. We identify knowledge gaps: There appears a bias to more easily accessible species (i.e., bottlenose dolphins and humpback whales), whereas there is a paucity of literature addressing vessel noise impacts on river dolphins, even though some of these species experience chronic noise from boats. Similarly, little is known about the potential effects of ship noise on pelagic and deep-diving marine mammals, even though ship noise is focused in a downward direction, reaching great depth at little acoustic loss and potentially coupling into sound propagation channels in which sound may transmit over long ranges. We explain the fundamental concepts involved in the generation and propagation of vessel noise and point out common problems with both physics and biology: Recordings of ship noise might be affected by unidentified artifacts, and noise exposure can be both under-and over-estimated by tens of decibel if the local sound propagation conditions are not considered. The lack of anthropogenic (e.g., different vessel types), environmental (e.g., different sea states or presence/absence of prey), and biological (e.g., different demographics) controls is a common problem, as is a lack of understanding what constitutes the 'normal' range of behaviors. Last but not least, the biological significance of observed responses is mostly unknown. Moving forward, standards on study design, data analysis, and reporting are badly needed so that results are comparable (across space and time) and so that data can be synthesized to address the grand unknowns: the role of context and the consequences of chronic exposures.

This study investigated intraspecific tooth rake scarring, an established indicator of received aggression by conspecifics, on bottlenose dolphins (Tursiops truncatus) to gain knowledge of aggressive interactions. The differences in tooth rake scarring between male and female dolphins on the east coast of Scotland were examined, and overall levels of scarring were compared with dolphins on the west coast of Scotland (Sound of Barra and Hebrides). Photographs were examined for evidence of tooth rake scarring using four different methods. East coast males displayed significantly higher scarring percentages (i.e., body area covered by tooth rake scarring), numbers of dorsal fin rake directions (i.e., whether tooth rake scars were vertical, horizontal, diagonal, or curved), and nick percentage (i.e., amount of the dorsal fin missing due to nicks) than females. Differences also existed between the three areas, with bottlenose dolphins around the Sound of Barra showing significantly lower levels of dorsal fin rake directions than those on the east coast or Hebrides. Observed sex differences are likely the result of intrasexual conflict between males over access to females. However, other factors such as sex-or age-specific behaviours or sexual coercion of females may also be involved. Such information could potentially be used to differentiate between the sexes. The differences in dorsal fin scarring between these populations suggests differences in aggressive interactions, possibly indicating differences in social structure. The lower scarring levels seen in the Sound of Barra group may support the suggestion that bottlenose dolphins on the west coast belong to two communities. However, this variability in conspecific aggression may also be the result of different social behaviours, age or sex ratios, habitat, resources, or individual behavioural differences.

The Covid-19 pandemic has brought about significant changes to most aspects of our lives. As a result of the quarantine enforced by governments and authorities worldwide, people had to suddenly adapt their daily routines, including work, study, diet, leisure and fitness activities to the new circumstances. A growing body of research indicates that the engagement with virtual reality (VR) activities can have a positive impact on users’ mental and physical wellbeing. This study aims to evaluate the impact of VR activities on users under lockdown due to the Covid-19 pandemic. An online survey was carried out to investigate the recreational use of VR during the lockdown period and to gather users’ opinions on its impact on their physical and mental health. Non-parametric tests were used to evaluate the statistical significance of the responses provided by the 646 participants. The results of the survey show that VR use has significantly increased during the lockdown period for most participants, who expressed overwhelmingly positive opinions on the impact of VR activities on their mental and physical wellbeing. Strikingly, self-reported intensity of physical activity was considerably more strenuous in VR users than in console users. Given the current uncertainty as to the duration and course of the pandemic, as well as the possibility of intermittent lockdown in the upcoming years, the outcomes of this study could have a significant impact towards the development and deployment of VR-based strategies aimed at helping the population cope with prolonged social distancing, with particular regards to vulnerable individuals.

AbstarctThe potential disturbance of dolphins from tourism boats has been widely discussed in the literature, in terms of both physical vessel presence and associated underwater noise. However, less attention has been paid to the potential impact of non-tourism vessels, despite these being much more widespread and occurring in greater numbers throughout coastal dolphin habitats. The Indo-Pacific bottlenose dolphin (T. aduncus) community using the Fremantle Inner Harbour, Western Australia, is exposed to high levels of vessel traffic. To investigate whether behavioural responses could be occurring, a non-invasive combination of visual and acoustic monitoring was conducted using a theodolite and an autonomous acoustic logger. Dolphins significantly increased their average movement speeds in high vessel densities, but only for some activity states. Behavioural budgets also changed in the presence of vessels, with animals spending greater time travelling and less time resting or socialising. Finally, multiple whistle characteristics varied with rising levels of broadband noise, and other contextual variables. Despite being acoustically specialised for higher frequencies, dolphins had the strongest acoustic variation during low-frequency noise. This study highlights the complexity of disturbance responses in this species, confirming the need for consideration of both surface and acoustic behaviour alongside appropriate contextual data.

The diversity, intensity, and periodicity of fish sounds can provide a wealth of information on spatial and temporal distribution of soniferous fish and, on occasion, which environmental factors these choruses are driven by. Such information can help predict species presence and understand their movement patterns in the long term. At three sites in Darwin Harbour, Australia, sea-noise loggers on the harbour floor recorded ambient noise over a 2-year period. Many fish calls and nine different chorus types were detected over 50 Hz to 3 kHz. Source species were speculated for four of the choruses and source levels, a precursor to passive acoustic abundance estimates, were identified for two of these. Other calls displayed similarities to choruses detected elsewhere in Australia. All choruses displayed diel cycles with semi-lunar patterns present for three of the chorus types. Time of sunset and temperature were also significantly related to the presence of the most predominant chorus and while not statistically significant, height of high tide and salinity also appeared related. A lack of frequency and temporal partitioning in calling across the choruses in hours of darkness (after sunset) illustrates the complexity of monitoring communities of different vocal species. The study has outlined some of the patterns biological sounds exhibit, which has significant implications for sampling strategies when using soundscapes for temporal and spatial predictive modelling.

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