William T. Ellison

Effect of anthropogenic low‐frequency noise on the foraging ecology of Balaenoptera whales

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 devel- opment, 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-fre- quency 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 distri- bution 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 peri- ods. 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.

Calibration and comparison of the acoustic location methods used during the spring migration of the bowhead whale, Balaena mysticetus, off Pt. Barrow, Alaska, 1984-1993

Between 1984 and 1993, visual and acoustic methods were combined to census the Bering-Chukchi-Beaufort bowhead whale, Balaena mysticetus, population. Passive acoustic location was based on arrival-time differences of transient bowhead sounds detected on sparse arrays of three to five hydrophones distributed over distances of 1.5-4.5 km along the ice edge. Arrival-time differences were calculated from either digital cross correlation of spectrograms (old method), or digital cross correlation of time waveforms (new method). Acoustic calibration was conducted in situ in 1985 at five sites with visual site position determined by triangulation using two theodolites. The discrepancy between visual and acoustic locations was <1%-5% of visual range and less than 0.7 degrees of visual bearing for either method. Comparison of calibration results indicates that the new method yielded slightly more precise and accurate positions than the old method. Comparison of 217 bowhead whale call locations from both acoustic methods showed that the new method was more precise, with location errors 3-4 times smaller than the old method. Overall, low-frequency bowhead transients were reliably located out to ranges of 3-4 times array size. At these ranges in shallow water, signal propagation appears to be dominated by the fundamental mode and is not corrupted by multipath.

Marine mammal noise exposure criteria: Initial scientific recommendations.

An expert panel reviewed the expanding literature on marine mammal (cetacean and pinniped) auditory and behavioral responses to sound exposure to develop comprehensive, scientifically based noise exposure criteria [Aquatic Mammals 33(4)]. They used precautionary extrapolation procedures to predict exposure levels above which adverse effects (both physical and behavioral) could be expected. Due to the paucity of data on long‐term exposures, criteria were developed for single exposure events only. Marine mammals were broken into functional hearing groups. Exposure types were lumped into three broad classes (single pulses, multiple pulses, and nonpulses). Levels estimated to induce permanent noise‐induced hearing loss were determined for each of 15 sound type/animal group combinations. For example, injury criteria for pinnipeds in water exposed to multiple pulses were 186 dB re 1 μPa2 ‐s (weighted SEL) and 218 dBpk re 1 μPa (unweighted peak SPL). Discrete behavioral disturbance thresholds could only be deter...

Acoustic Tracking of Migrating Bowhead Whales

An acoustic study was conducted off Point Barrow, Alaska in the springs of 1984 and 1985 on the bowhead whale, Balaena mysticetus, during their annual migration. Multi-channel tape recordings were made using arrays of sonobuoys, and whales were acoustically located using a customize hardware and software system specifically designed for performing sophisticated signal analyses. The system was field calibrated out to a distance of 4.5 km. The mean error in range to the source was 2.5%, while the mean error in bearing was 0.4 . At present, the acoustic analysis has concentrated on locating and tracking bowheads in order to census the whales and document their acoustic behavior as they move through and under the arctic ice. Results indicate that whales migrate through the area even during very rough ice conditions when visual observers see very few whales, many whales are more than 2.5 km offshore of the visual observation sites, whales that are within 2.5 km of the visual observers are often never seen, and whales use calls to communicate and maintain the cohesion of the herd.

Changes in Humpback Whale Song Occurrence in Response to an Acoustic Source 200 km Away

The effect of underwater anthropogenic sound on marine mammals is of increasing concern. Here we show that humpback whale (Megaptera novaeangliae) song in the Stellwagen Bank National Marine Sanctuary (SBNMS) was reduced, concurrent with transmissions of an Ocean Acoustic Waveguide Remote Sensing (OAWRS) experiment approximately 200 km away. We detected the OAWRS experiment in SBNMS during an 11 day period in autumn 2006. We compared the occurrence of song for 11 days before, during and after the experiment with song over the same 33 calendar days in two later years. Using a quasi-Poisson generalized linear model (GLM), we demonstrate a significant difference in the number of minutes with detected song between periods and years. The lack of humpback whale song during the OAWRS experiment was the most substantial signal in the data. Our findings demonstrate the greatest published distance over which anthropogenic sound has been shown to affect vocalizing baleen whales, and the first time that active acoustic fisheries technology has been shown to have this effect. The suitability of Ocean Acoustic Waveguide Remote Sensing technology for in-situ, long term monitoring of marine ecosystems should be considered, bearing in mind its possible effects on non-target species, in particular protected species.

Effects of mid-frequency active sonar on hearing in fish

Caged fish were exposed to sound from mid-frequency active (MFA) transducers in a 5 × 5 planar array which simulated MFA sounds at received sound pressure levels of 210 dB SPL(re 1 μPa). The exposure sound consisted of a 2 s frequency sweep from 2.8 to 3.8 kHz followed by a 1 s tone at 3.3 kHz. The sound sequence was repeated every 25 s for five repetitions resulting in a cumulative sound exposure level (SEL(cum)) of 220 dB re 1 μPa(2) s. The cumulative exposure level did not affect the hearing sensitivity of rainbow trout, a species whose hearing range is lower than the frequencies in the presented MFA sound. In contrast, one cohort of channel catfish showed a statistically significant temporary threshold shift of 4-6 dB at 2300 Hz, but not at lower tested frequencies, whereas a second cohort showed no change. It is likely that this threshold shift resulted from the frequency spectrum of the MFA sound overlapping with the upper end of the hearing frequency range of the channel catfish. The observed threshold shifts in channel catfish recovered within 24 h. There was no mortality associated with the MFA sound exposure used in this test.

An acoustic integration model (AIM) for assessing the impact of underwater noise on marine wildlife

In recent years there has been a heightened awareness of the environmental impact of noise, especially man‐made noise, on marine wildlife. The National Environmental Policy Act (NEPA), Executive Order 12114, The Endangered Species Act, The Marine Mammal Protection Act, and the Coastal Zone Management Act each provide for varying levels of regulation and control in protection of the environment and marine wildlife. In order to assess the environmental impact of a sound source, one must predict the sound levels that any given species will be exposed to over time in the locale of the source’s radiated field. This is a three‐part process involving (1) the ability to measure or predict an animal’s location in space in time, (2) the ability to measure or predict the sound field at these times and locations, and finally, (3) integration of these two data sets so as to determine the net acoustic impact of the sound source on any specific animal. This paper describes a modeling methodology for accomplishing this t...

Strategies for weighting exposure in the development of acoustic criteria for marine mammals

The Noise Exposure Criteria Group has been developing noise exposure criteria for marine mammals. Although the primary focus of the effort is development of criteria to prevent injury, the Group has also emphasized the development of exposure metrics that can be used to predict injury with accuracy and precision. Noise exposure metrics for humans have proven to be more effective when they account for psychophysical properties of the auditory system, particularly loudness perception. Usually noise is filtered using the A‐weighting function, an idealized curve based on the human 40‐phon equal loudness function. However, there are no empirical studies to show whether a comparable procedure for animals will improve predictions. The Noise Exposure Criteria Group panel has proposed to weight noise data by functions that admit sound throughout the frequency range of hearing in five marine mammal groupings—low frequency cetaceans (mysticetes), midfrequency cetaceans, high‐frequency cetaceans, pinnipeds in air, an...

Sound Exposure Guidelines

Chapters cannot be read stand-alone. Please see complete SpringerBrief at: http://link.springer.com/book/10.1007/978-3-319-06659-2.

A common sense approach to source metrics.

The analysis and assessment of the impact of anthropogenic sound on the ocean environment require a clear understanding of the spatial, spectral, and temporal properties of the sources that generate the sounds and the animals that are exposed. The mantra “spatial, spectral, and temporal” is one that applies to all acoustic assessment problems and should serve as the underlying basis for the analysis toolbox anyone brings to bear on these issues. Table 1 correlates the salient aspects of the three features of sound production, transmission, and reception with this mantra.