Exploring Geographic Variation in Fin Whale (Balaenoptera physalus) Calls From Two Passive Acoustic Monitoring Sites Revealing Population Identities Across the Weddell Sea, Antarctica

• Main Author: Field, Victoria R.
• Format: Thesis
• Language: unknown
• Published: 2021
• Subjects: Antarctic; Southern Ocean; Weddell Sea; Weddell; Greenwich; Elephant Island; Antarc*; Antarctica; Balaenoptera physalus; Fin whale
• Online Access: https://epic.awi.de/id/eprint/55894/; https://epic.awi.de/id/eprint/55894/1/Field_MSc_Thesis_Fin_Whales_2021.pdf; https://hdl.handle.net/10013/epic.20b1ff1d-9081-493a-80ce-549fbcb25fd4; https://hdl.handle.net/

Currently, little is known about the population identity of fin whales (Balaenoptera physalus) in Antarctic waters but initial analyses of acoustic recordings from the Southern Ocean (SO) have shown that fin whale calls differ between regions, possibly representing different fin whale populations. In the Atlantic Sector of the Southern Ocean, the typical fin whale 20-Hz song is often accompanied by simultaneous higher frequency (HF) component at around 89Hz or 99Hz. However, the distribution of these call types throughout the area and whether there is a clear spatial separation between these call types is so far unknown. In this study fin whale calls were examined between two locations, the Greenwich Meridian and Elephant Island across the Weddell Sea (from 2009, 2011, 2013, and 2015) to gain further insights into the connections between fin whales in this region. The HF call component was found to be significantly (p-value < 2.2e^-16) unique in its frequency at the two locations with 99Hz (97.14Hz ± 3.19) at Greenwich Meridian and 86Hz (86.26Hz ± 1.36) at Elephant Island. The inter-pulse interval (IPI) of both low frequency (LF) (20-Hz) and HF calls were also found to differ between geographic regions, with a median IPI of 14.5 seconds at Elephant Island and median IPI around 10 seconds at Greenwich Meridian. Variation in song IPIs were also investigated between geographic locations, Elephant Island was determined to have a majority singlet song type and Greenwich Meridian was found to have mostly triplet songs. The occurrence of HF and LF calls showed a strong positive correlation, indicating that both call components are produced simultaneously. The characteristic elements for fin whale calls examined in this study all indicate that the fin whale calls recorded at Elephant Island and Greenwich Meridian belong to two distinct acoustic populations. An understanding of how potentially distinct fin whale stocks utilize different geographic regions is fundamental for management and conservation measures aiming to improve the conservation status of this vulnerable species.