Characterizing patterns in endangered cetacean populations of the Hawaiian Archipelago using passive acoustic data

Abstract

Cetaceans play a vital ecological role in the marine environment as highly mobile top predators, but many species lack sufficient baseline data required for effective management and conservation. Cetacean population studies rely on the ability to accurately detect and identify the species, determine their location, estimate the number of animals or groups, and evaluate patterns in distribution. For endangered cetacean species, this information can be critical to their survival. Vessel-based visual observer surveys are the primary methods for studying cetacean populations, but these methods are limited by daylight, cetacean behavior, and poor weather conditions. Passive acoustic monitoring provides a technological approach for studying cetaceans using their vocalizations that is complementary to traditional visual observation methods. For this dissertation work, I developed and applied analytical methods that advance the use of acoustic data for cetacean population studies of endangered false killer whales (Pseudorca crassidens) and sperm whales (Physeter macrocephalus) in the Hawaiian Archipelago. My research addressed three components: (1) the utility of acoustic data to discriminate whistle characteristics of sympatric false killer whale populations, (2) the development of a localization algorithm for shallow towed linear arrays to improve the accuracy of 3-D positional estimates of cetaceans, and (3) a comparison of the environmental factors that predict the distribution of foraging versus non-foraging sperm whales. Each component of this research contributes important information for these endangered cetacean populations and guides future use of acoustic data in cetacean population studies.