Investigating the Movement and Seasonal Occurrence of Cetaceans in Hawai‘i Using Sound

Abstract

This dissertation tests two methods to obtain information of the distribution and movement of cetaceans. The first method uses vessels of opportunity as platforms to conduct acoustic surveys between the main Hawaiian Islands, with the ultimate goal of providing a method that can be used in future studies to contribute to mapping distribution and habitat modeling of data-poor cetacean species in the areas of the ocean which are infrequently surveyed. The distribution of a well-studied species, the humpback whale Megaptera novaeangliae was mapped and analyzed in relation to remotely sensed data on ocean depth, sea surface temperature, sea surface height, wind speed, chlorophyll-A, and surface currents. The results agreed with previous research on humpback whales, indicating that acoustic surveys from vessels of opportunity are a viable method for collecting distribution data on cetaceans. The predicted species of odontocete whistles collected during vessel of opportunity surveys was determined using the Real-time Odontocete Call Classification Algorithm, and analyzed in respect to remotely sensed data. The sighting rate for odontocete surveys in this study is comparable to that of previous survey methods, and cryptic species are identified at a higher relative rate than when using visual sighting methods. The biases inherent in concentrating survey effort primarily in the calm waters on the leeward sides the Hawaiian Islands are discussed, as well as the drawbacks of relying on visual sighting methods for detecting species with low visual detection probability. In addition, the potential impacts of anthropogenic noise and ship strikes from commercial vessels are discussed during the case study of a high-speed craft. This dissertation also discusses a second methodology involving the use of DIFAR sonobuoys to track multiple singing humpback whales, with the end goal of learning more about the function about humpback song. This method is also applicable to other cetacean species.