[Show abstract][Hide abstract] ABSTRACT: Ice seals overwintering in the Bering Sea are challenged with foraging, finding mates, and maintaining breathing holes in a dark and ice covered environment. Due to the difficulty of studying these species in their natural environment, very little is known about how the seals navigate under ice. Here we identify specific environmental parameters, including components of the ambient background sound, that are predictive of ice seal presence in the Bering Sea. Multi-year mooring deployments provided synoptic time series of acoustic and oceanographic parameters from which environmental parameters predictive of species presence were identified through a series of mixed models. Ice cover and 10 kHz sound level were significant predictors of seal presence, with 40 kHz sound and prey presence (combined with ice cover) as potential predictors as well. Ice seal presence showed a strong positive correlation with ice cover and a negative association with 10 kHz environmental sound. On average, there was a 20-30 dB difference between sound levels during solid ice conditions compared to open water or melting conditions, providing a salient acoustic gradient between open water and solid ice conditions by which ice seals could orient. By constantly assessing the acoustic environment associated with the seasonal ice movement in the Bering Sea, it is possible that ice seals could utilize aspects of the soundscape to gauge their safe distance to open water or the ice edge by orienting in the direction of higher sound levels indicative of open water, especially in the frequency range above 1 kHz. In rapidly changing Arctic and sub-Arctic environments, the seasonal ice conditions and soundscapes are likely to change which may impact the ability of animals using ice presence and cues to successfully function during the winter breeding season.
PLoS ONE 09/2014; 9(9):e106998. DOI:10.1371/journal.pone.0106998 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Acoustic time series are incredibly powerful as independent data sets. Passive acoustic recordings provide information on environmental sound levels, the presence of vocalizing animals, surface conditions, marine precipitation, and anthropogenic activities within the area of acoustic coverage. Active acoustic systems provide a time series of acoustic backscatter from which biological scatter can be measured and quantified to provide estimates of relative abundance and numerical density. The combination of acoustic technology with other hydrographic sensors within an ocean observing system now affords the opportunity to develop an understanding of ecosystem dynamics ranging from the physical oceanographic conditions to the distribution and behavior patterns of top predators. This is especially critical in sub-Arctic regions like the Bering Sea where rapid changes associated with climate change are having impacts at multiple levels. Here we discuss the environmental parameters that are the best predictors of different marine mammal species as determined through generalized linear and general additive mixed models. Predictor variables considered were percent ice cover, ice thickness, sound level at five frequencies, and percent composition of 4 biologic scattering groups.
The Journal of the Acoustical Society of America 09/2012; 132(3):1915. DOI:10.1121/1.4755028 · 1.50 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Many Pennsylvania reservoirs are created by clearing valleys prior to damming streams. These impoundments are typically devoid of appropriate benthic habitat for fish. The Pennsylvania Fish and Boat Commission has been placing artificial habitat structures in reservoirs across Pennsylvania for 30 years in an effort to increase game-fish production. However, the effectiveness of these efforts is unknown. Active acoustic technology is being considered as an alternative to conventional survey methods for assessing the effectiveness of artificial structure in F.J. Sayers Reservoir in Howard, PA. An autonomous echosounder [(ASL Environmental Sciences, 460 kHz Acoustic Water Column Profiler (AWCP)] was deployed horizontally near artificial rock structures to monitor associated fish activity. The AWCP recorded acoustic backscatter at 1-s intervals continuously for two days. Data was analyzed by (1) manually counting fish tracks on an echogram for each hour and range and (2) calculating integrated volume backscatter values per hour for each range. Both analysis methods showed similar trends in fish activity during the study period. Results agreed with expected behavioral patterns for the species in this body of water; fish activity increased during the night and decreased during the day, with the exception of a mid-day increase on one day.
The Journal of the Acoustical Society of America 10/2011; 130(4):2430. DOI:10.1121/1.3654742 · 1.50 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Artificial structures increase bottom complexity in man-made reservoirs and aim to increase fishery production by providing improved refuge, forage, and reproduction habitat. Electrofishing is typically employed to assess the effectiveness of these structures but is limited to shallow water sites. Active acoustic technology is a non-invasive sampling method that is more flexible than electrofishing, as it is operational in both deep and shallow water sites. Active acoustics also provides a continuous data series at one location to obtain high-temporal resolution information. An acoustic water column profiler was deployed for 1 week at each of two sites: (1) a control site with no introduced structure and (2) a treatment site with artificial refuge habitat. Difference in fish abundance, vertical distribution, and diurnal behavior between the two sites was assessed from the volume backscatter time series. Variation in fish activity between the two sites was compared. This work demonstrates the utility of active acoustics in assessing the effectiveness of freshwater habitat alteration beyond the scope of conventional techniques. A more comprehensive evaluation of habitat restoration is crucial in guiding the development of future conservation efforts.
The Journal of the Acoustical Society of America 03/2010; 127(3):1862. DOI:10.1121/1.3384455 · 1.50 Impact Factor