Biology Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2749
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Item Fish Bioacoustics: From Basic Science to Policy(2024) Colbert, Benjamin; Bailey, Helen R; Popper, Arthur N; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Sound is critically important to fishes. Sound is used to communicate with conspecifics, to detect predators and prey, or to otherwise understand the world around them. Within this dissertation, I used a variety of methods to investigate multiple aspects of fish bioacoustics, including hearing, hearing in noise, the effects of anthropogenic sound, and the morphology of peripheral auditory structures.In Chapter 2, I reviewed international policy on the regulation of underwater sound and the effects of underwater sound on marine and aquatic habitats. I found that while there are increasing efforts to regulate underwater noise, the policy efforts are hampered by a lack of quantifiable metrics associated with impacts of anthropogenic sound in aquatic habitats and species. In Chapter 3, I measured auditory sensitivity of cyprinids using physiological methods. Auditory evoked potentials, a physiological measure of auditory sensitivity, have been used in previous studies to measure hearing sensitivity. However, while physiological methods have their place, they are measuring the sensitivity of the ear rather than the entirety of the auditory pathway. Therefore, I further measured hearing sensitivity of goldfish using behavioral methods that encompass the full auditory pathway. I found that physiological methods tend to underestimate actual hearing sensitivity at frequencies less than 1000 Hz. In Chapter 4, I investigated cyprinid hearing in noise, using both physiological and behavioral measures. Critical ratios were measured for four species of carp and goldfish using auditory evoked potentials. Behavioral methods were also used to measure critical ratios for goldfish. These data represent the first measurements of critical ratios for carp and the first comparative analysis between critical ratios measured using both physiology and behavior. I found that critical ratios for carp increase by as much as 25 dB between 300 Hz and 1500 Hz. I also found that physiological methods likely overestimate actual critical ratios for fish. In Chapter 5, I used micro-computed tomography (micro-CT) and three dimensional geometric morphometrics to compare the peripheral auditory structures of three species of carp. Three dimensional models of the tripus ossicle, the posterior most Weberian ossicle, and the sagitta otolith were created and the shape of these structures for silver carp (Hypophthalmichthys molitrix), bighead carp (H. noblis), and grass carp (Ctenopharyngodon idella) quantified and contrasted. I found that the shape of the tripus differed between the Hypophthalmichthys genus (i.e., silver and bighead carp) and Ctenopharyngodon (grass carp), demonstrating a possible phylogenetic signal in the shape of the Weberian ossicles. In Chapter 6, I studied the response of wild oyster toadfish (Opsanus tau) to underwater radiated noise from boats. I used passive acoustic monitoring to record toadfish vocalizations and vessel passages in the Chesapeake Bay, U.S.A. The effect of acute vessel passage was determined by comparing the number of calls after a vessel had passed to a control period. The effect of both aggregate vessel passage over an hour and environmental variables were investigated using generalized additive mixed models. I found that there was no significant effect on toadfish call rates from acute vessel passage but when vessel generated sound was higher over an hour long period (i.e., aggregate effect), call rate declined.Item Ambient sound affects movement and calls of bottlenose dolphins(2021) Fandel, Amber Desneige; Bailey, Helen; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Abundant oceanic shipping and more frequent and intense storms are increasing sound levels in aquatic habitats. Understanding how changing soundscapes affect protected species, especially those that use sound to communicate and navigate, is critical. This study utilizes passive acoustic monitoring to investigate the effects of changing ambient sound levels on bottlenose dolphin (Tursiops truncatus) movements, spatial utilization, and social calls in the Mid-Atlantic Bight, USA. By localizing dolphin whistles, I determined that their habitat use changed under higher ambient sound levels and that these elevated sound levels caused dolphins to alter the acoustic characteristics of their calls. The acoustic characteristics of individually identifiable calls (signature whistles) also varied between the sites and regions in which they were recorded. As changes in the underwater soundscape continue in the future, these findings will help inform resource managers about how protected marine mammals may be affected by anthropogenic activities and sounds.Item THE ACOUSTIC QUALITIES THAT INFLUENCE AUDITORY OBJECT AND EVENT RECOGNITION(2019) Ogg, Mattson Wallace; Slevc, L. Robert; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Throughout the course of a given day, human listeners encounter an immense variety of sounds in their environment. These are quickly transformed into mental representations of objects and events in the world, which guide more complex cognitive processes and behaviors. Through five experiments in this dissertation, I investigated the rapid formation of auditory object and event representations (i.e., shortly after sound onset) with a particular focus on understanding what acoustic information the auditory system uses to support this recognition process. The first three experiments analyzed behavioral (dissimilarity ratings in Experiment 1; duration-gated identification in Experiment 2) and neural (MEG decoding in Experiment 3) responses to a diverse array of natural sound recordings as a function of the acoustic qualities of the stimuli and their temporal development alongside participants’ concurrently developing responses. The findings from these studies highlight the importance of acoustic qualities related to noisiness, spectral envelope, spectrotemporal change over time, and change in fundamental frequency over time for sound recognition. Two additional studies further tested these results via syntheszied stimuli that explicitly manipulated these acoustic cues, interspersed among a new set of natural sounds. Findings from these acoustic manipulations as well as replications of my previous findings (with new stimuli and tasks) again revealed the importance of aperiodicity, spectral envelope, spectral variability and fundamental frequency in sound-category representations. Moreover, analyses of the synthesized stimuli suggested that aperiodicity is a particularly robust cue for some categories and that speech is difficult to characterize acoustically, at least based on this set of acoustic dimensions and synthesis approach. While the study of the perception of these acoustic cues has a long history, a fuller understanding of how these qualities contribute to natural auditory object recognition in humans has been difficult to glean. This is in part because behaviorally important categories of sound (studied together in this work) have previously been studied in isolation. By bringing these literatures together over these five experiments, this dissertation begins to outline a feature space that encapsulates many different behaviorally relevant sounds with dimensions related to aperiodicity, spectral envelope, spectral variability and fundamental frequency.Item SPATIAL AND TEMPORAL DYNAMICS OF THE CHESAPEAKE BAY SEA NETTLE(2018) Shahrestani, Suzan; Bi, Hongsheng; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The jellyfish Chrysaora chesapeakei forms large summer blooms in Chesapeake Bay, and has substantial ecological and economic impacts on local ecosystems. Limited information on this species is mostly due to difficulties collecting spatial information on jellyfish in dynamic coastal ecosystems. Spatial gaps of C. chesapeakei were addressed by applying a multi-scale approach across life stages and within a source-sink context, reflected by the ecology and habitat utilization of C. chesapeakei. An Adaptive Resolution Imaging System (ARIS, SoundMetrics, Inc.) was used to collect high-resolution data on medusae in 2016 and 2017, within a Patuxent River waterscape. Polyp settlement plates were deployed at eight sites to understand the distributional range of the sessile benthic stage in Chesapeake Bay, but polyps successfully overwintered at only one of the sites, indicating that settlement alone was insufficient to explain C. chesapeakei dispersal to new habitat. Using high-resolution sonar data, a multi-scale spatial analysis was conducted to understand medusae dispersion and abundance. Medusae were three times more abundant in 2017 than in 2016. However, differences in water-column concentration were not apparent at the fine-scale (<5m) where medusae were randomly dispersed in both years. At the mesoscale (10km), spatial dependency was observed in both years, with more transport of jellyfish to dispersal habitat in the high-abundance year (2017). Overall, polyp settlement and overwintering survival in potential habitat seem to control the spatial distribution of C. chesapeakei at the Bay-wide scale while medusae appear responsible for mesoscale dispersal to new habitat, demonstrating high dispersal to sink habitat in a high-density year and low dispersal in a low-density year.Item THE ROLE OF FREQUENCY, TIMING AND LEVEL DISTORTION ON BINAURAL PROCESSING IN SIMULATIONS OF COCHLEAR IMPLANT USERS WITH SINGLE-SIDED DEAFNESS(2017) Wess, Jessica Marie; Bernstein, Joshua GW; Gordon-Salant, Sandra; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Cochlear implants are a promising new treatment option for single-sided deafness. Cochlear implants for single-sided deafness have been shown to improve speech perception in noise and aid in sound localization. However, this intervention is not as good as acoustic hearing and listeners’ exhibit large amounts of variability in hearing outcomes. These limitations may be caused by certain distortions inherent in the processing of the sound signals by the cochlear implant. This dissertation examined the role that three key cochlear implant distortions might play in limiting speech perception in noise for listeners with single-sided deafness. The first distortion examined was the frequency mismatch between the cochlear implant and the acoustic ear. The next distortion examined was the effect of timing differences between the cochlear implant and the normal hearing ear. Finally, the effect of compression on hearing speech in spatial noise was investigated. These limitations and distortions could limit binaural processing ability in those with single-sided deafness who receive a cochlear implant. The goal of this dissertation was to examine the role of cochlear-implant distortions on binaural hearing using simulations of cochlear implant processing presented to normal-hearing listeners. Normal-hearing listeners were presented with vocoder simulations of cochlear-implant processing to one ear, and unprocessed signals to the other ear. These simulations were used to examine the ability to understand binaural speech signals in noisy environments and to examine auditory object formation in simulated free-field environments. These data provided insight into how CI distortions and mapping strategies can limit binaural benefits for those with single-sided deafness. Knowledge of these limitations could lead to better programming strategies to improve binaural hearing and quality of life for those with single-sided deafness who receive a cochlear implant.