Marine renewable energy development raised concerns over the impact of underwater noise. Here we assess the acoustic impacts of an operating tidal current turbine (Paimpol-Bréhat site, France) on marine fauna. Its source level (SL) has been measured in situ using 19 drifting transects at distances between 100 m to 2400 m from the turbine. SL ranged from 118 to 152 dB re1 μ[email protected] m in third-octave bands at frequencies between 40 and 8192 Hz. It is comparable to the SL of a 19 m boat travelling at 10kt speed. This SL was used to estimate the impact of this noise type based on acoustic propagation simulations. The acoustic footprint of the device corresponds to a 1.5 km radius disk. Our results show that within this area of greatest potential impact, physiological injury of the hearing apparatus of invertebrates, fishes and marine mammals is improbable. Behavioral disturbance may occur up to 1 km around the device for harbor porpoises only. This is of little concern for a single turbine. However, greater concern on turbine noise impact, particularly on behavioral reactions has to be granted for a farm with up to 100 turbine. The lack of consolidated knowledge on behavioral disturbances identifies the needs for specific research programs.
Soundscapes and Acoustics
This paper is the first to address the environmental legal issues that could arise from the conduct of unilateral seismic operations in disputed maritime areas. And that should be surprising: such operations are ongoing in many places across the globe as states seek to enhance their domestic natural resource potentials and establish their sovereign control in the areas under dispute. But, the lack of previous legal scholarship on the topic is even more surprising when one realises the serious and multifaceted risks posed by seismic surveys on the marine environment. As this paper discusses, there are known environmental risks that include permanent injuries to marine organisms or even immediate death. Other effects may include temporary injuries that may or may not directly result in death but that may make marine organisms less fit, resulting in lower chances of survival. These risks are in addition to less well understood but nonetheless plausible risks to marine ecosystems, such as the potential for noise-derived behavioural disturbance. This could have an impact on animals’ feeding, movement and reproduction, and might also have short- or long-term effects on catch success rates. The paper examines the possible application of provisional measures of protection under Article 290 of the United Nations Convention on the Law of the Sea (UNCLOS). This provision enables a court or tribunal exercising jurisdiction under UNCLOS to prescribe provisional measures not only to preserve the rights of the disputants, but also, or even solely, to prevent serious harm to the marine environment. The analysis explores the foreseeable risks posed by unilateral seismic surveys and examines if Article 290 of UNCLOS provides adequate protection to the complainant state against such operations, pending the final settlement of the dispute. The paper reviews the existing environmental jurisprudence of the International Tribunal for the Law of the Sea (ITLOS) on provisional measures and comments on the potential to respond meaningfully to unilateral seismic exploration activities in disputed maritime areas through recourse to provisional measures of protection.
The seasonal occupancy and diel behaviour of sperm whales (Physeter macrocephalus) was investigated using data from long-term acoustic recorders deployed off east Antarctica. An automated method for investigating acoustic presence of sperm whales was developed, characterised, and applied to multi-year acoustic datasets at three locations. Instead of focusing on the acoustic properties of detected clicks, the method relied solely on the inter-click-interval (ICI) for determining presence within an hour-long recording. Parameters for our classifier were informed by knowledge of typical vocal behaviour of sperm whales. Sperm whales were detected predominantly from Dec-Feb, occasionally in Nov, Mar, Apr, and May, but never in the Austral winter or early spring months. Ice cover was found to have a statistically significant negative effect on sperm whale presence. In ice-free months sperm whales were detected more often during daylight hours and were seldom detected at night, and this effect was also statistically significant. Seasonal presence at the three east Antarctic recording sites were in accord with what has been inferred from 20th century whale catches off western Antarctica and from stomach contents of whales caught off South Africa.
Anthropogenic noise pollution is recognized as a major global stressor of animals. While many studies have assessed the unimodal impacts of noise pollution with a focus on intraspecific acoustic communication, little is known about noise pollution on the perception of visual and chemical information. The ‘distracted prey hypothesis’ posits that processing noise interferes with processing other information in the brain. Here, we found evidence for such a cross-modal effect of noise on the antipredator behaviour of a freshwater prey fish, the fathead minnow, Pimephales promelas. In laboratory trials, exposure to noise from a motorboat caused the total absence of the classical fright reaction of minnows to conspecific alarm cues, whereas an ambient noise control had no such impact. In natural habitats, the impairment of such antipredator behaviour due to noise pollution could have major fitness consequences. We discuss how our findings translate to animal ecology and the need for future studies that target specific management decisions regarding noise pollution.
Anthropogenic noise across the world's oceans threatens the ability of vocalizing marine species to communicate. Some species vocalize at key life stages or whilst foraging, and disruption to the acoustic habitat at these times could lead to adverse consequences at the population level. To investigate the risk of these impacts, we investigated the effect of vessel noise on the communication space of the Bryde's whale Balaenoptera edeni, an endangered species which vocalizes at low frequencies, and bigeye Pempheris adspersa, a nocturnal fish species which uses contact calls to maintain group cohesion while foraging. By combining long-term acoustic monitoring data with AIS vessel-tracking data and acoustic propagation modelling, the impact of vessel noise on their communication space was determined. Routine vessel passages cut down communication space by up to 61.5% for bigeyes and 87.4% for Bryde's whales. This influence of vessel noise on communication space exceeded natural variability for between 3.9 and 18.9% of the monitoring period. Additionally, during the closest point of approach of a large commercial vessel, <10 km from the listening station, the communication space of both species was reduced by a maximum of 99% compared to the ambient soundscape. These results suggest that vessel noise reduces communication space beyond the evolutionary context of these species and may have chronic effects on these populations. To combat this risk, we propose the application or extension of ship speed restrictions in ecologically significant areas, since our results indicate a reduction in sound source levels for vessels transiting at lower speeds.
Over the last decade the issue of underwater noise pollution has received increased attention from scientific bodies, the media, NGOs, and institutions at the national, supranational and international levels. This in turn, has led to the development of several regulatory initiatives that seek to mitigate the negative impact of this source of pollution. This article outlines and analyses existing legislation and management regimes that govern marine activities that generate noise. Best practices and specific mitigation measures are also addressed and assessed.
Destructive fishing using explosives occurs in a number of countries worldwide, negatively impacting coral reefs and fisheries on which millions of people rely. Documenting, quantifying and combating the problem has proved problematic. In March–April 2015 231 h of acoustic data were collected over 2692 km of systematically laid transects along the entire coast of Tanzania. A total of 318 blasts were confirmed using a combination of manual and supervised semi-autonomous detection. Blasts were detected along the entire coastline, but almost 62% were within 80 km of Dar es Salaam, where blast frequency reached almost 10 blasts/h. This study is one of the first to use acoustic monitoring to provide a spatial assessment of the intensity of blast fishing. This can be a useful tool that can provide reliable data to define hotspots where the activity is concentrated and determine where enforcement should be focused for maximum impact.
Canadian Arctic and Subarctic regions experience a rapid decrease of sea ice accompanied with increasing shipping traffic. The resulting time-space changes in shipping noise are studied for four key regions of this pristine environment, for 2013 traffic conditions and a hypothetical tenfold traffic increase. A probabilistic modeling and mapping framework, called Ramdam, which integrates the intrinsic variability and uncertainties of shipping noise and its effects on marine habitats, is developed and applied. A substantial transformation of soundscapes is observed in areas where shipping noise changes from present occasional-transient contributor to a dominant noise source. Examination of impacts on low-frequency mammals within ecologically and biologically significant areas reveals that shipping noise has the potential to trigger behavioral responses and masking in the future, although no risk of temporary or permanent hearing threshold shifts is noted. Such probabilistic modeling and mapping is strategic in marine spatial planning of this emerging noise issues.
An alternate management system is introduced which uses seasonal and spatially explicit multi-species quotas generated from small-scale cooperative fishery acoustic surveys to manage the Aleutian Islands walleye pollock (Gadus chalcogrammus) fishery while limiting impacts on the endangered Western stock of Steller sea lions (Eumetopias jubatus). This is a novel collaboration among scientists, industry, and Alaska Natives considering a cooperative management approach. The proposed system integrates the catch monitoring and accounting systems already in place in the federal groundfish fisheries off Alaska with cooperative acoustic survey biomass estimates to facilitate more refined spatial and temporal fishery management decisions. Conditions were examined under which such a system could operate successfully and results from field work conducted to assess technical requirements were discussed. During field trials biomass estimates from each survey were produced within 24-h of survey completion. This suggests spatial abundance estimates can be available in a timely manner for managing local fisheries. The proposed management system was found feasible and relatively easy to initiate because of highly motivated and cooperative industry partners, a well-established mechanism for setting allowable catch limits, and a robust catch accounting system already in place. In addition, high quality commercial echosounders required for this system are currently used by industry and, with proper controls on calibration and survey design, produce biomass estimates of sufficient quality. The application of this approach beyond this case study is also discussed for managing fisheries worldwide where fine temporal and spatial scale management could benefit the conservation of other protected species.
Hydroacoustic technologies are widely used in fisheries research but few studies have used them to examine the effects of Marine Protected Areas (MPAs). We evaluate the efficacy of hydroacoustics to examine the effects of closure to fishing and habitat type on fish populations in the Cabo Pulmo National Park (CPNP), Mexico, and compare these methods to Underwater Visual Censuses (UVC). Fish density, biomass and size were all significantly higher inside the CPNP (299%, 144% and 52% respectively) than outside in non-MPA control areas. These values were much higher when only accounting for the reefs within the CPNP (4715%, 6970% and 97% respectively) highlighting the importance of both habitat complexity and protection from fishing for fish populations. Acoustic estimates of fish biomass over reef-specific sites did not differ significantly from those estimated using UVC data, although acoustic densities were less due to higher numbers of small fish recorded by UVC. There is thus considerable merit in nesting UVC surveys, also providing species information, within hydroacoustic surveys. This study is a valuable starting point in demonstrating the utility of hydroacoustics to assess the effects of coastal MPAs on fish populations, something that has been underutilised in MPA design, formation and management.