The ambient acoustic environment in Laguna San Ignacio, Baja California Sur, Mexico (original) (raw)
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Previous research has speculated that diffuse ambient noise levels can be used to estimate relative cetacean abundance in certain locations when baleen whale vocal activity dominates the soundscape (Au et al., 2000; Mellinger et al., 2009). During the 2013 and 2014 humpback whale breeding seasons off Los Cabos, Mexico, visual point and line transects were conducted alongside two bottom-mounted acoustic deployments. As theorized, preliminary analysis of ambient noise between 100-1000 Hz is dominated by humpback whale song. It also displays a diel cycle similar to that found in the West Indies, Australia, and Hawai’i whereby peak levels occur near midnight and troughs occur soon after sunrise (Au et al., 2000; McCauley et al., 1996). Depending upon site and year, the median band-integrated levels fluctuated between 7 to 16 dB re 1 uPa when sampled in one hour increments. This presentation uses analytical models of wind-generated noise in an ocean waveguide to analyze potential relationships between singing whale density and diffuse ambient noise levels. It explores whether various diel cycle strengths (peak-to-peak measurements and Fourier analysis) correspond with trends observed from concurrent visual censuses. [Work sponsored by the Ocean Foundation.]
The Journal of the Acoustical Society of America
Passive acoustic monitoring of ocean soundscapes can provide information on ecosystem status for those tasked with protecting marine resources. In 2015, the National Oceanic and Atmospheric Administration (NOAA) established a long-term, continuous, low-frequency (10 Hz-2 kHz) passive acoustic monitoring site in the Cordell Bank National Marine Sanctuary (CBNMS), located offshore of the central United States of America (U.S.) west coast, near San Francisco, CA. The California Current flows southward along the coast in this area, supporting a diverse community of marine animals, including several baleen whale species. Acoustic data analysis revealed that both large vessels and vocalizing baleen whales contribute to the ambient soundscape of the CBNMS. Sound levels fluctuated by month with the highest levels in the fall and lowest levels in the summer. Throughout the year, very low-frequency (10-100 Hz) sound levels were most variable. Vessels and whales overlap in their contributions to ambient sound levels within this range, although vessel contributions were more omnipresent, while seasonal peaks were associated with vocalizing whales. This characterization of low-frequency ambient sound levels in the CBNMS establishes initial baselines for an important component of this site's underwater soundscape. Standardized monitoring of soundscapes directly supports NOAA's ability to evaluate and report on conditions within national marine sanctuaries.
Conservation Biology, 2012
The effects of chronic exposure to increasing levels of human-induced underwater noise on marine animal populations reliant on sound for communication are poorly understood. We sought to further develop methods of quantifying the effects of communication masking associated with human-induced sound on contact-calling North Atlantic right whales (Eubalaena glacialis) in an ecologically relevant area (∼10,000 km 2 ) and time period (peak feeding time). We used an array of temporary, bottom-mounted, autonomous acoustic recorders in the Stellwagen Bank National Marine Sanctuary to monitor ambient noise levels, measure levels of sound associated with vessels, and detect and locate calling whales. We related wind speed, as recorded by regional oceanographic buoys, to ambient noise levels. We used vessel-tracking data from the Automatic Identification System to quantify acoustic signatures of large commercial vessels. On the basis of these integrated sound fields, median signal excess (the difference between the signal-to-noise ratio and the assumed recognition differential) for contact-calling right whales was negative (−1 dB) under current ambient noise levels and was further reduced (−2 dB) by the addition of noise from ships. Compared with potential communication space available under historically lower noise conditions, calling right whales may have lost, on average, 63-67% of their communication space. One or more of the 89 calling whales in the study area was exposed to noise levels ≥120 dB re 1 μPa by ships for 20% of the month, and a maximum of 11 whales were exposed to noise at or above this level during a single 10-min period. These results highlight the limitations of exposure-threshold (i.e., dose-response) metrics for assessing chronic anthropogenic noise effects on communication opportunities. Our methods can be used to integrate chronic and wide-ranging noise effects in emerging ocean-planning forums that seek to improve management of cumulative effects of noise on marine species and their habitats.
Park Science
M ALE HUMPBACK WHALES (MEGAPTERA NOVAE-ANGLIAE) (fi g. 1) produce "songs"—long, patterned sequences of sounds—that are presumed to function as a reproductive display on the breeding grounds (Payne and McVay 1971; Winn and Winn 1978; Tyack 1981). Many preferred breeding areas are conservation hot spots protected by marine parks, and the whale-watching industry has fl ourished in those sites (Hoyt 2001). Noise generated from whale-watching boat traffi c can mask important aspects of whale communication. This raises concerns about the potential infl uence of noise on repro-ductive success and population growth. Gray whales may tempo-rarily or permanently abandon critical areas because of excessive exposure to boat noise (Bryant et al. 1984). Therefore, managers in parks created to protect and conserve whales are often faced with the task of managing noise-generating tourism activities, especially in breeding areas. Because whales are acoustic specialists (Richardson et al. 19...
Underwater vessel noise in a commercial and tourist bay complex in the Mexican Central Pacific
Ciencias Marinas
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...
Endangered Species Research
Anthropogenic noise negatively impacts many species. One of the more insidious effects of elevated noise levels is the reduction in area over which animals are able to acoustically communicate, often termed communication masking. This study utilizes modeling approaches to evaluate relative levels of masking for 4 baleen whale species from the combination of current ambient noise conditions and noise from discrete vessels operating in the Stellwagen Bank National Marine Sanctuary. Acoustic data were collected using bottom-mounted autonomous recorders. One day was analyzed for each of 5 different species-specific sound types, corresponding to peaks in occurrence of fin and humpback whale songs, humpback whale social sounds, minke whale pulse trains and North Atlantic right whale gunshots. Source levels for animals and 3 categories of vessels were calculated empirically; sound propagation was modeled using Bellhop ray tracing. An agent-based modeling framework was used to calculate changes in communication space (CS) in comparison to reference conditions (10 dB lower than current ambient noise). In these singleday snapshots, current ambient noise and noise from vessels for which automatic identification system (AIS) data were available contribute most heavily to loss of CS, followed by whale-watching and fishing vessels. Right whale gunshots experience the least amount of masking, while fin, humpback and minke whale signals experience masking levels of 80% or more. While these results incorporate several simplifying assumptions, this study further develops the framework by which to comparatively quantify masking, providing information on the relative degree of masking experienced between species and allowing for important insights on the relative contributions of different anthropogenic sound sources.
Frontiers in Marine Science
Soundscapes with minimal anthropogenic noise sources are key for the survival and effective communication of marine mammals. The Gulf of Tribugá is part of the breeding ground for humpback whale Stock G. Currently, no large-scale infrastructure exists on the Gulf's coastline, making it an area with high biodiversity and little anthropogenic noise. Whale-watching is one of the few human activities that contributes to the soundscape. By Morro Mico, on the southern limit of the Utría Natural National Park, an Ecological Acoustic Recorder (EAR, Oceanwide Science Institute) was deployed in the Gulf to record samples of acoustic activity from October to November 2018. It recorded for 10-min intervals with 20-min lapses for a duty cycle of 33.3%. One of the common peak frequencies of humpback whale song units from these recordings was used as input to an acoustic propagation model using the parabolic equation to simulate the communication space of a humpback whale when zero, one, and t...
Effect of anthropogenic low-frequency noise on the foraging ecology of Balaenoptera whales
Animal Conservation, 2001
The human contribution to ambient noise in the ocean has increased over the past 50 years, and is dominated by low-frequency (LF) sound (frequencies <1000 Hz) from shipping, oil and gas development, defence-related and research activities. Mysticete whales, including six endangered species, may be at risk from this noise pollution because all species produce and probably perceive low-frequency sound. We conducted a manipulative field experiment to test the effects of loud, LF noise on foraging fin blue (B. musculus) and (Balaenoptera physalus) whales off San Nicolas Island, California. Naive observers used a combination of attached tracking devices, ship-based surveys, aerial surveys, photo-identification and passive monitoring of vocal behaviour to examine the behaviour and distribution of whales when a loud LF source (US Navy SURTASS LFA) was and was not transmitting. During transmission, 12-30% of the estimated received levels of LFA of whales in the study area exceeded 140 dB re 1 µPa. However, whales continued to be seen foraging in the region. Overall, whale encounter rates and diving behaviour appeared to be more strongly linked to changes in prey abundance associated with oceanographic parameters than to LF sound transmissions. In some cases, whale vocal behaviour was significantly different between experimental and non-experimental periods. However, these differences were not consistent and did not appear to be related to LF sound transmissions. At the spatial and temporal scales examined, we found no obvious responses of whales to a loud, anthropogenic, LF sound. We suggest that the cumulative effects of anthropogenic LF noise over larger temporal and spatial scales than examined here may be a more important consideration for management agencies.