| Summary: | Dissertation (Ph.D.) University of Alaska Fairbanks, 2015 Cook Inlet beluga whales (CIBs) are a geographically and genetically isolated population residing in Cook Inlet, Alaska year round. The population declined by approximately 50% between 1994 and 1998 and was listed as endangered under the Endangered Species Act in 2008. The original decline was attributed to overharvest; however, the population has failed to rebound despite the virtual absence of harvest since 1998. This suggests that other factors, such as declining prey availability, increased predation, contaminants, disease, climate change, catastrophic events, habitat loss, unauthorized take, and underwater noise pollution, may be limiting the population's recovery. The goal of this dissertation research was to study the potential impacts of underwater noise on the CIB population. The objective of Chapter 1 was to study CIB acoustic behavior to gain a greater understanding of how CIBs utilize sound. The objective of Chapter 2 was to measure underwater sound levels in Cook Inlet to understand the background noise levels with which CIBs must cope. The objective of Chapter 3 was to document reactions of CIBs to noise disturbance utilizing local ecological knowledge to allow insight into the potential impacts of noise on beluga behavior. The results of Chapter 1 showed that belugas exhibit significant seasonal and spatial variation in calling behavior which suggested differences in habitat usage or differences in the surrounding environment, including background noise levels. The results of Chapter 2 showed that root mean square sound pressure levels exhibited high variation with the highest levels recorded in the 100 Hz frequency band. The seasonal differences in sound levels observed in this study were likely due to greater small vessel traffic and oil and gas development activities in the summer than the winter. In Chapter 3, participants reported observations of CIBs exhibiting avoidance reactions to noise sources including boats, planes, ...
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