If these walls could talk: Investigating bottlenose dolphin habitat use in fiord ecosystems

Abstract

Effective management of protected species requires a comprehensive understanding of their ecology. Within the Te Moana o Atawhenua-FiordlandMarine Area (FMA), Aotearoa-New Zealand, two of the four recognized bottlenose dolphin (Tursiops truncatus) sub-populations are considered to exclusively inhabit discrete fiord systems. Opportunistic sightings outside the Patea-Doubtful and Tamatea-Dusky fiord complexes, however, suggest they occupy a larger space than currently recognized. To investigate the presence of bottlenose dolphins in five neighboring fiord systems, passive acoustic monitoring (PAM) was conducted from February 2022 to November 2023. PAM effort included two instrumentation approaches: F-PODs to continuously detect click trains of odontocetes, and SoundTraps to provide broad spectrum recordings (15 of every 30 min, sampling rate: 96kHz). This study discusses the trade-offs between approaches in terms of cost, recording duration, and data collected. In addition, photo-identification of bottlenose dolphins in these neighboring fiords was used to identify the sub-population of individuals. The results demonstrate that bottlenose dolphins are regularly using fiords that are not formally considered part of their range within the FMA. A greater understanding of the spatial ecology of Fiordland bottlenose dolphin sub-populations necessitates consideration of threats and resources both inside and outside of their namesake fiord complexes.