Movements and Spatial Use of Odontocetes in the western Main Hawaiian Islands: Results of a Three-year Study off O‘ahu and Kaua‘i

Abstract

A long-term assessment of odontocete populations throughout the main Hawaiian Islands has involved small-boat surveys using photo-identification, genetic sampling and satellite tagging, to address questions related to population structure and habitat use, among others. Prior to 2010 we had undertaken limited field operations off O‘ahu (in 2002 and 2003), and off of Kaua‘i (in 2003, 2005 and 2008). Navy training activities may take place throughout the Hawai‘i Range Complex, however many of the training exercises are undertaken in the western main Hawaiian Islands, in particular at the Pacific Missile Range Facility (PMRF) off Kaua‘i and Ni‘ihau. As part of an effort to reduce uncertainty regarding the population structure, range, and abundance of odontocetes in the western main Hawaiian Islands, to help inform Navy impact assessments, we undertook small-boat based research efforts off O‘ahu (in 2010) and off Kaua‘i (in 2011 and 2012). These efforts utilized a variety of field methods to obtain data sets relevant to assessing these population characteristics, including photo-identification, collection of biopsy samples for genetic studies, and satellite tagging. Over the three years of the project surveys were undertaken on 66 days (406 hours), covering 6,559 km. Overall there were 191 odontocete sightings, 183 of which were identified to species. Off O‘ahu there were 30 sightings of 10 species, while off Kaua‘i and Ni‘ihau there were 153 sightings of eight species. One hundred and two biopsy samples were collected from seven different species for genetics and toxicology studies. Thirty satellite tags were deployed on five species: pygmy killer whales, false killer whales, bottlenose dolphins, rough-toothed dolphins, and short-finned pilot whales. For all five species, tag data indicate that there are island-associated populations. Our efforts substantially increased what is known about the movements and habitat use of these five species of odontocetes in the western main Hawaiian Islands